Apple Talk Connections to Services Drop

Symptom Users complain that their AppleTalk sessions suddenly drop for no apparent reason. Table 9-8 outlines the problem that might cause this symptom and describes solutions to that -problem. Table 9-8 AppleTalk Connections to Services Drop Table 9-8 AppleTalk Connections to Services Drop Excessive traffic load on internetworks with many routers can prevent some routers from sending RTMP updates every 10 seconds as they should. Because routers begin to age out routes after missing two...

Apple Talk Enhanced IGRP Clients Cannot Connect to Servers

Symptom Macintosh clients cannot connect to servers in an AppleTalk Enhanced IGRP network environment. Table 9-11 outlines the problems that might cause this symptom and describes solutions to those problems. Table 9-11 AppleTalk Enhanced IGRP Clients Cannot Connect to Servers Table 9-11 AppleTalk Enhanced IGRP Clients Cannot Connect to Servers Routers not establishing neighbors properly For information on troubleshooting this problem, see the section AppleTalk Enhanced IGRP Routers Not...

Apple Talk Enhanced IGRP Poor Performance

Symptom Network performance in an AppleTalk Enhanced IGRP environment is poor. Connections between clients and servers are slow or unreliable. Table 9-14 outlines the problems that might cause this symptom and describes solutions to those problems. Table 9-14 AppleTalk Enhanced IGRP Poor Performance AppleTalk Enhanced IGRP and RTMP are running simultaneously on the same interface Use the show running-config privileged exec command on network routers. Check the interface configurations to...

Apple Talk Enhanced IGRP Routers Not Establishing Neighbors

Symptom AppleTalk Enhanced IGRP routers do not establish neighbors properly. Routers that are connected do not appear in the neighbor table. Table 9-12 outlines the problems that might cause this symptom and describes solutions to those problems. Table 9-12 AppleTalk Enhanced IGRP Routers Not Establishing Neighbors Table 9-12 AppleTalk Enhanced IGRP Routers Not Establishing Neighbors AppleTalk Enhanced IGRP is not globally configured on the appropriate routers Step 1 Use the show running-config...

Apple Talk Enhanced IGRP Routes Missing from Routing Table

Symptom Routes are missing from the routing table of routers running AppleTalk Enhanced IGRP. Clients (Macintosh computers) on one network cannot access servers on a different network. Clients might or might not be able to connect to servers on the same network. The problem might occur in internetworks running only Enhanced IGRP or in an internetwork running Enhanced IGRP and RTMP. Table 9-13 outlines the problems that might cause this symptom and describes solutions to those problems. Table...

Apple Talk Interface Fails to Initialize Apple Talk

Symptom Router interface connected to a network will not initialize AppleTalk. Table 9-9 outlines the problems that might cause this symptom and describes solutions to those problems. Table 9-9 AppleTalk Interface Fails to Initialize AppleTalk Step 1 Use the show appletalk interface exec command. Check the output for a port configuration mismatch message. If the command output contains a mismatch message, the router configuration disagrees with that of the listed neighbor. If the command output...

Apple Talk Network Services Intermittently Unavailable

Symptom Network services are intermittently unavailable. Services come and go without warning. Table 9-6 outlines the problems that might cause this symptom and describes solutions to those problems. Table 9-6 AppleTalk Network Services Intermittently Unavailable Table 9-6 AppleTalk Network Services Intermittently Unavailable Duplicate network numbers or overlapping cable-range In AppleTalk, network numbers must be unique within an internetwork. If duplicate network numbers exist, packets might...

Apple Talk No Devices in Chooser

Symptom Zones appear in the Chooser, but when a service (such as AppleShare) and a zone are selected, no devices appear in the device list. Table 9-5 outlines the problem that might cause this symptom and describes solutions to that -problem. Table 9-5 AppleTalk No Devices in Choose Step 1 Use the show appletalk access-list exec command on routers in the path from source to destination. Step 2 Disable any access lists (or just those on a particularly suspect router) using the no appletalk...

Apple Talk Old Zone Names Appear in Chooser Phantom Zones

Symptom Old AppleTalk zone names continue to appear in the Chooser. Even after zone names are removed from the configuration, phantom zones continue to appear in the Chooser. Table 9-7 outlines the problems that might cause this symptom and describes solutions to those problems. Table 9-7 AppleTalk Old Zone Names Appear in Chooser (Phantom Zones) Table 9-7 AppleTalk Old Zone Names Appear in Chooser (Phantom Zones) Step 1 Use the show appletalk interface exec command. Check the output for a port...

Apple Talk Port Stuck in Restarting or Acquiring Mode

Symptom A router port is stuck in restarting or acquiring mode (as shown in the output of the show apple interface privileged exec command). The router cannot discover routes or poll neighbors on an attached cable. Table 9-10 outlines the problems that might cause this symptom and describes solutions to those problems. Table 9-10 AppleTalk Port Stuck in Restarting or Acquiring Mode Table 9-10 outlines the problems that might cause this symptom and describes solutions to those problems. Table...

Apple Talk Technology Basics

AppleTalk was designed as a client server distributed network system. In other words, users share network resources (such as files and printers) with other users. Computers supplying these network resources are called servers computers using a server's network resources are called clients. Interaction with servers is essentially transparent to the user because the computer itself determines the location of the requested material and accesses it without further information from the user. In...

Apple Talk Users Cannot Access Zones or Services

Symptom Users cannot access zones or services that appear in the Chooser. Users might or might not be able to access services on their own network. Table 9-2 outlines the problems that might cause this symptom and describes solutions to those problems. Table 9-2 AppleTalk Users Cannot Access Zones or Services Table 9-2 AppleTalk Users Cannot Access Zones or Services Step 1 Use the show appletalk interface exec command. Check the output for a port configuration mismatch message. If the command...

Apple Talk Zones Missing from Chooser

Symptom Certain zones do not appear in the Chooser. The zones are not visible from multiple networks. In some cases, when the Chooser is opened, the zone list changes. Table 9-4 outlines the problems that might cause this symptom and describes solutions to those problems. Table 9-4 AppleTalk Zones Missing from Chooser Step 1 Use the show appletalk interface exec command. Check the output for a port configuration mismatch message. If the command output contains a mismatch message, the router...

Ara Ara Client Unable to Connect to ARA Server

Symptom An ARA client (such as a Macintosh) attempts to connect to an ARA server (such as a Cisco access server) and cannot initiate a remote session. The user might be able to connect briefly, but the connection is immediately terminated. Table 9-18 outlines the problems that might cause this symptom and describes solutions to those problems. Table 9-18 ARA ARA Client Unable to Connect to ARA Server Table 9-18 ARA ARA Client Unable to Connect to ARA Server Step 1 Use the show running-config...

ARA Cannot Send or Receive Data over ARA Dialin Connection

Symptom ARA connections are established, but users cannot send or receive ARA data over the link. Table 9-20 outlines the problems that might cause this symptom and describes solutions to those problems. Table 9-20 ARA Cannot Send or Receive Data over ARA Dialin Connection Table 9-20 ARA Cannot Send or Receive Data over ARA Dialin Connection Step 1 Use the show running-config privileged exec command to view the router configuration. If you are running Cisco IOS Release 10.2 or later, look for...

ARA Connection Hangs After Communicating At Message

Symptom An ARA client (for example, a Macintosh) tries to connect to an ARA server (such as a Cisco access server) over client and server modems. The client receives a connect message such as Communicating at 14.4 Kbps but then hangs for 10-30 seconds and finally shows a connection failed message. Table 9-19 outlines the problem that might cause this symptom and describes solutions to that problem. Table 9-19 ARA Connection Hangs After Communicating At Message Table 9-19 ARA Connection Hangs...

ARA Slow Performance from Dialin Connection

Symptom Performance on remote dialin ARA sessions is slow. Table 9-21 outlines the problem that might cause this symptom and describes solutions to that problem. Table 9-21 ARA Slow Performance from Dialin Connection Table 9-21 ARA Slow Performance from Dialin Connection Flow control is not enabled, is enabled only on one device (either DTE or DCE), or is misconfigured Step 1 Configure hardware flow control on the line using the flowcontrol hardware line configuration command. Hardware flow...

Aurp

AURP allows a network administrator to connect two or more AppleTalk internetworks through a foreign network (such as Transmission Control Protocol Internet Protocol TCP IP ) to form an AppleTalk wide-area network (WAN). The connection is called a tunnel, which functions as a single, virtual data link between the AppleTalk internetworks, as shown in Figure 9-6. A router that connects an AppleTalk internetwork to a tunnel (that is, a router that runs AURP) is called an exterior router. The...

AURP Routes Not Propagated Through AURP Tunnel

Symptom AppleTalk routes are not propagated through an AURP tunnel. Routes that are known to exist on one side of the tunnel do not appear in the routing tables of the exterior router on the other side of the tunnel. Changes on the remote network (such as a route going down) are not learned by the exterior router on the other side of the tunnel. Table 9-16 outlines the problems that might cause this symptom and describes solutions to those problems. Table 9-16 AURP Routes Not Propagated Through...

BGP Routers Not Advertising Routes

Symptom BGP routers are not advertising routes. Routing updates from a BGP router do not contain information about certain network destinations that should be advertised. Table 7-17 outlines the problems that might cause this symptom and describes solutions to those problems. Table 7-17 BGP Routers Not Advertising Routes Table 7-17 BGP Routers Not Advertising Routes Missing network router configuration command Step 1 Use the show running-config privileged exec command to view the router...

BGP Routes Missing from Routing Table

Symptom BGP routers and networks are not advertised to other routers. Routers do not receive routing information from other routers. Some hosts cannot communicate with hosts in other areas, and routing table information is incomplete. Table 7-16 outlines the problems that might cause this symptom and describes solutions to those problems. Table 7-16 BGP Routes Missing from Routing Table Table 7-16 BGP Routes Missing from Routing Table If BGP routers are not advertising routes properly, routing...

Cddi

The high cost of fiber-optic cable has been a major impediment to the widespread deployment of FDDI to desktop computers. At the same time, shielded twisted-pair (STP) and unshielded twisted-pair (UTP) copper wire is relatively inexpensive and has been widely deployed. The implementation of FDDI over copper wire is known as Copper Distributed Data Interface (CDDI). Before FDDI could be implemented over copper wire, a problem had to be solved. When signals strong enough to be reliably...

Cisco Product Documentation

Installation and configuration guides, switch software guides, configuration notes, and more. CDDI FDDI Adapters and Concentrators (Catalyst 1200 thru 6000 Series, Ethernet Switches) (LightStream, Catalyst 8510 MSR & 8540 MSR) (Access Gateways, CallManager, IP Phones) Access Servers and Access Routers Core High-End Routers (Cisco AGS+, Cisco 7x00 series routers, Cisco 1x000 series routers, Cisco Optical Regenerator, Cisco Optical Network System products) 10BaseT Hubs Internet Services...

Datagram Delivery Protocol

AppleTalk's primary network-layer protocol is the Datagram Delivery Protocol (DDP). DDP provides connectionless service between network sockets. Sockets can be assigned either statically or dynamically. AppleTalk addresses, which are administered by the DDP, consist of two components a 16-bit network number and an 8-bit node number. The two components are usually written as decimal numbers, separated by a period (for example, 10.1 means network 10, node 1). When an 8-bit socket identifying a...

Digital Network Architecture

Contrary to popular belief, DECnet is not a network architecture at all but is, rather, a series of products conforming to Digital's Digital Network Architecture (DNA). Like most comprehensive network architectures from large systems vendors, DNA supports a large set of both proprietary and standard protocols. The list of DNA-supported technologies grows constantly as Digital implements new protocols. Figure 11-1 illustrates an incomplete snapshot of DNA and the relationship of some of its...

FDDITalk No Zone Associated with Routes

Symptom Routers on an FDDI ring have routes to networks across the ring, but no zones are associated with the routes. The output of the show appletalk route command indicates no zone set for those routes. Note On other media, routes with no zone set are the result of other problems, such as ZIP storms. See the sections AppleTalk Zones Missing from Chooser and AppleTalk Network Services Intermittently Unavailable in this chapter for more information. Table 9-17 outlines the problem that might...

Frame Format

FDDI frame formats (shown in Figure 5-7) are similar to those of Token Ring. Figure 5-7 FDDI Frame Format The fields of an FDDI frame are as follows Preamble Prepares each station for the upcoming frame. Start delimiter Indicates the beginning of the frame. It consists of signaling patterns that differentiate it from the rest of the frame. Frame control Indicates the size of the address fields, whether the frame contains asynchronous or synchronous data, and other control information....

General Problem Solving Model

When you're troubleshooting a network environment, a systematic approach works best. Define the specific symptoms, identify all potential problems that could be causing the symptoms, and then systematically eliminate each potential problem (from most likely to least likely) until the symptoms disappear. Figure 1-1 illustrates the process flow for the general problem-solving model. This process flow is not a rigid outline for troubleshooting an internetwork it is a foundation from which you can...

Internet Group Membership Protocol

Internet Group Membership Protocol (IGMP), defined in RFC 1112, relies on Class D IP addresses for the creation of multicast groups. By using a specific Class D address, an individual host dynamically registers itself in a multicast group. Hosts identify their group memberships by sending IGMP messages. Traffic is then sent to all members of that multicast group. Routers listen to IGMP messages and periodically send out queries to discover which groups are active on which LANs. To build...

Internet Routing

Routing devices in the Internet have traditionally been called gateways---an unfortunate term because elsewhere in the industry, the term gateway applies to a device with somewhat different functionality. Gateways (which we will call routers from this point on) within the Internet are organized hierarchically. Some routers are used to move information through one particular group of networks under the same administrative authority and control (such an entity is called an autonomous system)....

Internetwork Design Guide

Internetworking Design Basics Designing Large-Scale IP Internetworks Designing SRB Internetworks Designing SDLC, SDLLC, and QLLC Internetworks Designing APPN Internetworks Designing DLSw+ Internetworks Designing ATM Internetworks Designing Packet Service Internetworks Designing DDR Internetworks Designing ISDN Internetworks Designing Switched LAN Internetworks Designing Internetworks for Multimedia Appendix A Subnetting an IP Address Space Appendix B IBM Serial Link Implementation Notes...

Internetworking Case Studies

RIP and OSPF Redistribution Increasing Security on IP Networks Integrating Enhanced IGRP into Existing Networks Reducing SAP Traffic in Novell IPX Networks STUN for Front-End Processors Using ISDN Effectively in Multiprotocol Networks Using HSRP for Fault-Tolerant IP Routing Multicasting in IP and AppleTalk Networks Scaling Dial-on-Demand Routing Using the Border Gateway Protocol for Interdomain Routing HOME CONTENTS PREVIOUS NEXT GLOSSARY FEEDBACK SEARCH Copyright 1989-2000 Cisco Systems Inc.

Internetworking Terms and Acronyms

Cisco Systems Terms and Acronyms Copyright 1989-2000 Cisco Systems Inc. Cisco - Feedback Content-Type text html Cisco - Feedback Content-Type text html Did this (or your previous) CCO visit save you a call to Cisco Your feedback is vital to our goal of making CCO the most useful and informative website on the planet. Please let us know how we are doing and, more importantly, what we can improve. CCO's breadth of information & services CCO's perceived speed or responsiveness Overall...

IP Enhanced IGRP Router Stuck in Active Mode

Symptom An IP Enhanced IGRP router is stuck in Active mode. Multiple Stuck-in-Active messages are sent to the console DUAL-3-SIA Route 198.169.52.51 Stuck-in-Active For a more detailed explanation of Enhanced IGRP Active mode, see the section Enhanced IGRP and Active Passive Modes later in this chapter. Note Occasional messages of this type are not a cause for concern. This is how an Enhanced IGRP router recovers if it does not receive replies to its queries from all its neighbors. However, if...

IP Enhanced IGRP Routers Not Establishing Neighbors

Symptom Enhanced IGRP routers are not establishing neighbor relationships properly. Routing information is not distributed to routers. Table 7-13 outlines the problems that might cause this symptom and describes solutions to those problems. Table 7-13 IP Enhanced IGRP Routers Not Establishing Neighbors Table 7-13 IP Enhanced IGRP Routers Not Establishing Neighbors Misconfigured or missing network router configuration command Step 1 Use the show ip eigrp neighbors exec command on an Enhanced...

IPX Enhanced IGRP No Connectivity over IPX Enhanced IGRP Router

Symptom IPX Enhanced IGRP routers are blocking connections. Clients cannot connect to servers over one or more routers running IPX Enhanced IGRP. Note Procedures for troubleshooting connectivity problems not specific to IPX Enhanced IGRP routing are described in the section Novell IPX Client Cannot Connect to Server on Remote LAN earlier in this chapter. Table 8-8 outlines the problems that might cause this symptom and describes solutions to those problems. Table 8-8 IPX Enhanced IGRP No...

IPX Enhanced IGRP Routers Not Establishing Neighbors

Symptom IPX Enhanced IGRP routers do not establish neighbors properly. Routers that are known to be connected do not appear in the neighbor table. Note Procedures for troubleshooting IPX Enhanced IGRP problems not specific to establishing neighbors are described in the section 'IPX Enhanced IGRP No Connectivity over IPX Enhanced IGRP Router earlier in this chapter. Table 8-9 outlines the problems that might cause this symptom and describes solutions to those problems. Table 8-9 IPX Enhanced...

Local SRB Host Cannot Connect to Server

Symptom Connections fail over a router configured as an SRB connecting two or more Token Rings. Table 10-1 outlines the problems that might cause this symptom and describes solutions to those problems. Table 10-1 Local SRB Host Cannot Connect to Server Table 10-1 Local SRB Host Cannot Connect to Server A router interface configured for bridging fails to insert into a ring when it detects a ring number mismatch, and posts an error message to the console. Step 1 Get the ring number (specified in...

Local SRB Routing Does Not Function

Symptom Routed protocols are not forwarded properly by routers in a local SRB environment. SRBs bridge traffic normally. Table 10-2 outlines the problems that might cause this symptom and describes solutions to those problems. Table 10-2 Local SRB Routing Does Not Function Table 10-2 Local SRB Routing Does Not Function For detailed information on troubleshooting routing problems, refer to the chapters in this book that cover the routing protocols in question. For example, if you are running...

Media Problems Token Ring

Table 6-1 outlines problems commonly encountered on Token Ring networks and offers general guidelines for solving those problems. Table 6-1 Media Problems Token Ring Table 6-1 Media Problems Token Ring Step 1 Use the show interfaces token command to determine the status of the router's Token Ring interfaces. Step 2 If the status line indicates that the interface and line protocol are not up, check the cable from the router to the MAU.1 Make sure that the cable is in good condition. If it is...

Navigating Cisco Connection Documentation CDROM

Cisco Connection Documentation CD-ROM is a series of interconnected documents that you navigate by clicking on hypertext links and using the navigation tools---the toolbar, the navigation bar, and the document button bar. In addition, Cisco Connection Documentation CD-ROM offers a powerful search facility to allow you to jump directly to the information that interests you. Cisco Connection Documentation CD-ROM also provides several ways to return to documents that you have previously looked at....

Novell IPX Client Cannot Connect to Server on Remote LAN

Symptom Clients cannot make connections to servers on another network over one or more routers interconnected by LAN networks. Clients can connect to servers on their local network. Table 8-2 outlines the problems that might cause this symptom and describes solutions to those problems. Note If clients cannot connect to servers on their local network, refer to the section Novell IPX Client Cannot Connect to Server on Same LAN earlier in this chapter. If there is a WAN network between the local...

Novell IPX Client Cannot Connect to Server on Same LAN

Symptom Clients cannot make connections to servers located on the same LAN. Also, clients cannot connect to servers on remote networks. Table 8-1 outlines the problems that might cause this symptom and describes solutions to those problems. Table 8-1 Novell IPX Client Cannot Connect to Server on Same LAN Table 8-1 Novell IPX Client Cannot Connect to Server on Same LAN Step 1 Make sure the software on both clients and servers is the current version, is configured correctly, and has loaded...

Novell IPX Client Cannot Connect to Server over ISDN

Symptom Clients cannot connect to servers over an ISDN link. Clients can connect to local servers. Note Procedures for troubleshooting connectivity problems not specific to ISDN environments are described in the section Novell IPX Client Cannot Connect to Server on Remote LAN earlier in this chapter. Procedures for troubleshooting ISDN connectivity problems not specific to IPX environments are described in Chapter 17, Troubleshooting ISDN Connections. Table 8-4 outlines the problems that might...

Novell IPX Clients Cannot Connect to Server over PSN

Symptom Clients cannot connect to servers over a packet-switched network (PSN), such as Frame Relay, X.25, or SMDS. Clients can connect to local servers. Note Procedures for troubleshooting connectivity problems not specific to PSN environments are described in the section Novell IPX Client Cannot Connect to Server on Remote LAN earlier in this chapter. Table 8-3 outlines the problems that might cause this symptom and describes solutions to those problems. Table 8-3 Novell IPX Client Cannot...

Novell IPX Intermittent Connectivity

Symptom Connectivity between clients and servers is intermittent. Clients might be able to connect some of the time, but at other times no connectivity to certain servers or networks is possible. Table 8-12 outlines the problems that might cause this symptom and describes solutions to those problems. Table 8-lZ Novell IPX Intermittent Connectivity Table 8-lZ Novell IPX Intermittent Connectivity Step 1 Use the show running-config privileged exec command to view the router configuration. Look for...

Novell IPX Slow Performance

Symptom Slow network performance is experienced in a Novell IPX network. Table 8-13 outlines the problems that might cause this symptom and describes solutions to those problems. Table 8-lS Novell IPX Slow Performance Table 8-lS Novell IPX Slow Performance Novell servers not processing SAP updates as quickly as router is generating them Step 1 Use the show interfaces privileged exec command to check for output drops. Step 2 If there are excessive drops, use the show ipx servers exec command on...

Novell NetBIOS Applications Cannot Connect to Server over Router

Symptom Applications that use Novell NetBIOS (such as Windows 95) cannot connect to servers over a router. Clients cannot connect to servers on the same LAN. Table 8-5 outlines the problems that might cause this symptom and describes solutions to those problems. Table 8-5 Novell NetBIOS Applications Cannot Connect to Server over Router Table 8-5 Novell NetBIOS Applications Cannot Connect to Server over Router Missing ipx type-20-propagation commands Step 1 Use the debug ipx packet privileged...

Novell Technology Basics

As an NOS environment, NetWare specifies the upper five layers of the OSI reference model. It provides file and printer sharing, support for various applications, such as electronic mail transfer and database access, and other services. Like other NOSs, such as the Network File System (NFS) from Sun Microsystems, Inc., and LAN Manager from Microsoft Corporation, NetWare is based on a client server architecture. In such architectures, clients (sometimes called workstations) request certain...

OSPF Routers Not Establishing Neighbors

Symptom OSPF routers are not establishing neighbor relationships properly. The result is that routing information is not exchanged between routers. Table 7-11 outlines the problems that might cause this symptom and describes solutions to those problems. Table 7-11 OSPF Routers Not Establishing Neighbors Table 7-11 OSPF Routers Not Establishing Neighbors Step 1 Use the show ip ospf interfaces exec command to determine which interfaces have OSPF1 enabled. Step 2 If the output indicates that an...

Preparing for Network Failure

It is always easier to recover from a network failure if you are prepared ahead of time. Possibly the most important requirement in any network environment is to have current and accurate information about that network available to the network support personnel at all times. Only with complete information can intelligent decisions be made about network change, and only with complete information can troubleshooting be done as quickly and easily as possible. During the process of troubleshooting...

Protocol Address Assignment

To ensure minimal network administrator overhead, AppleTalk node addresses are assigned dynamically. When a Macintosh running AppleTalk starts up, it chooses a protocol (network-layer) address and checks whether that address is currently in use. If it is not, the new node has successfully assigned itself an address. If the address is currently in use, the node with the conflicting address sends a message indicating a problem, and the new node chooses another address and repeats the process....

RSRB Host Cannot Connect to Server Peers Not Open

Symptom Hosts cannot make connections to servers across a router configured as a remote source-routing bridge (RSRB). The output of the show source-bridge privileged exec command shows that SRB peers are not open. Note If you succeed in getting peers to open but hosts are still unable to communicate with servers, refer to the section RSRB Host Cannot Connect to Server (Peers Open) later in this chapter. Table 10-3 outlines the problems that might cause this symptom and describes solutions to...

RSRB Host Cannot Connect to Server Peers Open

Symptom Hosts cannot make connections to servers across a router configured as an RSRB. The output of the show source-bridge privileged exec command shows that SRB peers are open. The following is an example of output from the show source-bridge command Peers state lv pkts_rx pkts_tx expl_gn drops TCP TCP 150.136.93.93 open 2* 18 18 3 0 0 Table 10-4 outlines the problems that might cause this symptom and describes solutions to those problems. Table 10-4 RSRB Host Cannot Connect to Server (Peers...

RSRB NetBIOS Client Cannot Connect to Server

Symptom NetBIOS clients cannot connect to NetBIOS servers over a router configured as an RSRB. Table 10-6 outlines the problems that might cause this symptom and describes solutions to those problems. Table 10-6 RSRB NetBIOS Client Cannot Connect to Server Table 10-6 RSRB NetBIOS Client Cannot Connect to Server Step 1 For each router on which NetBIOS name caching is enabled, use the show rif exec command to determine whether the RIF entry shows the correct path from the router to both the...

RSRB Periodic Communication Failures

Symptom Communication failures occur periodically over a router configured as an RSRB. Table 10-6 outlines the problems that might cause this symptom and describes solutions to those problems. Table 10-5 RSRB Periodic Communication Failures Table 10-5 RSRB Periodic Communication Failures If you are not using local acknowledgment, misconfigured T1 timers can cause periodic timeouts. Step 1 Use a network analyzer to see how long it takes for packets to travel from one end of the network to the...

Sample Display

The following is sample output from the show interfaces tokenring command Router show interfaces tokenring TokenRing 0 is up, line protocol is up Hardware is 16 4 Token Ring, address is 5500.2000.dc27 (bia 0000.3000.072b) Internet address is 150.136.230.203, subnet mask is 255.255.255.0 MTU 8136 bytes, BW 16000 Kbit, DLY 630 usec, rely 255 255, load 1 255 Encapsulation SNAP, loopback not set, keepalive set (10 sec) ARP type SNAP, ARP Timeout 4 00 00 Ring speed 16 Mbps Single ring node, Source...

SDLC Router Cannot Communicate with SDLC Device

Symptom Router cannot communicate with an IBM SDLC device. Table 10-9 outlines the problems that might cause this symptom and describes solutions to those problems. Table 10-9 SDLC Router Cannot Communicate with SDLC Device Table 10-9 SDLC Router Cannot Communicate with SDLC Device Step 1 Use the show interfaces exec command to determine whether the interface and line protocol are up. Step 2 If the interface and line protocol are both up, troubleshoot link-layer problems as described later in...

Serial Lines Increasing Carrier Transitions Count on Serial Link

Carrier transitions appear in the output of the show interfaces serial exec command whenever there is an interruption in the carrier signal (such as an interface reset at the remote end of a link). Symptom Increasing carrier transitions count on serial link. Table 15-7 outlines the possible problems that might cause this symptom and describes solutions to those problems. Table 15-7 Serial Lines Increasing Carrier Transitions Count on Serial Link The following problems can result in this symptom...

Serial Lines Increasing Input Drops on Serial Link

Input drops appear in the output of the show interfaces serial exec command (refer to Figure 15-1) when too many packets from that interface are still being processed in the system. Symptom Increasing number of input drops on serial link. Table 15-3 outlines the possible problem that might cause this symptom and describes solutions to that problem. Table 15-3 Serial Lines Increasing Input Drops on Serial Link Table 15-3 Serial Lines Increasing Input Drops on Serial Link Input rate exceeds the...

Serial Lines Increasing Input Errors in Excess of 1 of Total Interface Traffic

If input errors appear in the show interfaces serial output (refer to Figure 15-1), there are several possible sources of those errors. The most likely sources are summarized in Table 15-4. Note Any input error value for cyclic redundancy check (CRC) errors, framing errors, or aborts above 1 percent of the total interface traffic suggests some kind of link problem that should be isolated and repaired. Symptom Increasing number of input errors in excess of 1 percent of total interface traffic....

Serial Lines Increasing Output Drops on Serial Link

Output drops appear in the output of the show interfaces serial command (refer to Figure 15-1) when the system is attempting to hand off a packet to a transmit buffer but no buffers are available. Symptom Increasing output drops on serial link. Table 15-2 outlines the possible problem that might cause this symptom and describes solutions to that problem. Table 15-2 Serial Lines Increasing Output Drops on Serial Link Table 15-2 Serial Lines Increasing Output Drops on Serial Link Input rate to...

Serial Lines Troubleshooting Serial Line Input Errors

Table 15-5 describes the various types of input errors displayed by the show interfaces serial command (see Figure 15-1), possible problems that might be causing the errors, and solutions to those problems. Table 15-5 Serial Lines Troubleshooting Serial Line Input Errors Table 15-5 Serial Lines Troubleshooting Serial Line Input Errors CRC errors occur when the CRC calculation does not pass (indicating that data is corrupted) for one of the following reasons Serial cable is too long or cable...

SRB Algorithm

SRBs are so named because they assume that the complete source-to-destination route is placed in all inter-LAN frames sent by the source. SRBs store and forward the frames as indicated by the route appearing in the appropriate frame field. Figure 10-3 illustrates a sample SRB network. Referring to Figure 10-3, assume that Host X wishes to send a frame to Host Y. Initially, Host X does not know whether Host Y resides on the same or a different LAN. To determine this, Host X sends out a test...

SRT Bridging Client Cannot Connect to Server

Symptom Clients cannot communicate over a router configured to perform SRT bridging. Packets are not forwarded by the SRT bridge. Note SRT bridging allows you to implement transparent bridging in Token Ring environments. It is not a means of translating between SRB on a Token Ring and transparent bridging on Ethernet (or other) media. Table 10-8 outlines the problems that might cause this symptom and describes solutions to those problems. Table 10-8 SRT Bridging Client Cannot Connect to Server...

Subnet Broadcast

Subnet broadcast (defined in RFC 922) supports the sending of packets to all the subnets of a particular network number. Packet duplication occurs when there are alternative paths in a network. In Figure 7-10, when Workstation A uses subnet broadcasting to send a packet to each workstation on Subnetwork 2, a duplicate packet also arrives. Whenever there is a duplicate path in the network, a duplicate packet is delivered. Because many multicast applications are data intense, packet duplication...

Table of Contents

Cisco Connection Documentation CD-ROM Help What is Cisco Connection Documentation CD-ROM Cisco Connection Documentation CD-ROM User Interface Navigating Cisco Connection Documentation CD-ROM Hypertext Links Table of Contents Illustrations Tables Searching the Current Document Searching Multiple Documents Configuring Adobe Acrobat Reader as a Helper Application

TCPIP Host Connections Fail Using Certain Applications

Symptom Connection attempts using some applications are successful, but attempts using other applications fail. For instance, you might be able to ping a host successfully, but Telnet connections fail. Table 7-6 outlines the problems that might cause this symptom and describes solutions to those problems. Table 7-6 TCP IP Host Connections Fail Using Certain Applications Table 7-6 TCP IP Host Connections Fail Using Certain Applications Misconfigured access lists or other filters Step 1 Use the...

TCPIP Local Host Cannot Access Remote Host

Symptom Hosts on one network cannot communicate with hosts on a remote network. The networks are separated by one or more routers and might include WAN or other links. One or more routing protocols are running on the routers. Table 7-3 outlines the problems that might cause this symptom and describes solutions to those problems. Table 7-3 TCP IP Local Host Cannot Access Remote Host Table 7-3 TCP IP Local Host Cannot Access Remote Host Default gateway is not specified or is misconfigured on...

TCPIP Poor Performance

Symptom Performance for one or more network hosts is slow. Connections to servers take an excessive amount of time to establish. Table 7-8 outlines the problems that might cause this symptom and describes solutions to those problems. Misconfigured resolv.conf file on DNS client Check the etc resolv.conf file on DNS clients. If the file is misconfigured, the client might wait until a query to one server times out before trying a second server, an NISi, or its host tables. This can cause...

TCPIP Routing Not Functioning Properly on New Interface

Symptom A new interface is added to a router, but when routing is configured, it does not function properly on the new interface. Table 7-5 outlines the problems that might cause this symptom and describes solutions to those problems. Table 7-5 TCP IP Routing Not Functioning Properly on New Interface Table 7-5 TCP IP Routing Not Functioning Properly on New Interface Step 1 Use the show interfaces privileged exec command to see whether the interface is administratively down Router show interface...

The Network Layer

IP is the primary Layer 3 protocol in the Internet protocol suite. In addition to internetwork routing, IP provides fragmentation and reassembly of datagrams and error reporting. Along with TCP, IP represents the heart of the Internet Protocol suite. The IP packet format is shown in Figure 7-2. The fields of the IP packet are as follows Version Indicates the version of IP currently used. IP header length (IHL)---Indicates the datagram header length in 32-bit words. Type-of-service Specifies how...

The Transport Layer

VINES provides three transport-layer services Unreliable datagram service Sends packets that are routed on a best-effort basis but not acknowledged at the destination. Reliable message service---A virtual-circuit service that provides reliable sequenced and acknowledged delivery of messages between network nodes. A reliable message can be transmitted in a maximum of four VIP packets. Data stream service Supports the controlled flow of data between two processes. The data stream service is an...

The Vlan Director Switch Management Application

The VlanDirector switch management application simplifies VLAN port assignment and offers other management capabilities for VLANs. VlanDirector offers the following features for network administrators Accurate representation of the physical network for VLAN design and configuration -verification Capability to obtain VLAN configuration information on a specific device or link interface Discrepancy reports on conflicting configurations Ability to troubleshoot and identify individual device...

Token RingIEEE 8025 Comparison

Token Ring and IEEE 802.5 networks are basically quite compatible, but the specifications differ in relatively minor ways. IBM's Token Ring network specifies a star, with all end stations attached to a device called a multistation access unit (MAU), whereas IEEE 802.5 does not specify a topology (although virtually all IEEE 802.5 implementations also are based on a star). Other differences exist, including media type (IEEE 802.5 does not specify a media type, whereas IBM Token Ring networks use...

Troubleshooting DECnet

This section presents protocol-related troubleshooting information for DECnet Phase IV connectivity and performance problems. The procedures outlined apply only to environments in which DECnet routing is enabled on the router, not to environments in which DECnet is being bridged (that is, bridging is enabled on the router interfaces and EtherType 6003 is being passed). This chapter does not discuss other Digital protocols, such as Maintenance Operation Protocol (MOP), local-area transport...

Troubleshooting Fiber Distributed Data Interface

FDDI Specifications Physical Connections Traffic Types Fault-Tolerant Features Frame Format CDDI Syntax Description Command Mode Usage Guidelines Sample Displays Troubleshooting Fiber Distributed Data Interface The Fiber Distributed Data Interface (FDDI) standard was produced by the ANSI X3T9.5 standards committee in the mid-1980s. During this period, high-speed engineering workstations were beginning to tax the capabilities of existing local-area networks (LANs)---primarily Ethernet and Token...

Troubleshooting Novell IPX

Novell Technology Basics Media Access The Network Layer The Transport Layer Upper-Layer Protocols Troubleshooting Novell IPX Novell IPX Client Cannot Connect to Server on Same LAN Novell IPX Client Cannot Connect to Server on Remote LAN Novell IPX Clients Cannot Connect to Server over PSN Novell IPX Client Cannot Connect to Server over ISDN Novell NetBIOS Applications Cannot Connect to Server over Router IPX RIP No Connectivity over IPX RIP Router IPX RIP SAP Updates Not Propagated by Router...

Troubleshooting TCPIP

Internet Protocols The Network Layer Addressing Internet Routing ICMP IRDP Distance Vector Multicast Routing Protocol Multicast Open Shortest Path First Protocol Independent Multicast Comparison of Multicast Routing Protocols Troubleshooting TCP IP TCP IP Local Host Cannot Access Remote Host TCP IP Routes Learned from the Wrong Interface or Protocol Split Horizon Example TCP IP Routing Not Functioning Properly on New Interface TCP IP Host Connections Fail Using Certain Applications...

Troubleshooting Token Ring

The Token Ring network was originally developed by IBM in the 1970s. It is still IBM's primary local-area network (LAN) technology, and is second only to Ethernet IEEE 802.3 in general LAN popularity. The IEEE 802.5 specification is almost identical to, and completely compatible with, IBM's Token Ring network. In fact, the IEEE 802.5 specification was modeled after IBM Token Ring, and continues to shadow IBM's Token Ring development. The term Token Ring is generally used to refer to both IBM's...

Tuning System Buffers

There are two general buffer types on Cisco routers hardware buffers and system buffers. Only the system buffers are directly configurable by system administrators. The hardware buffers are specifically used as the receive and transmit buffers associated with each interface and (in the absence of any special configuration) are dynamically managed by the system software itself. The system buffers are associated with the main system memory and are allocated to different-size memory blocks. A...

Upper Layer Protocols

The Internet Protocol suite includes many upper-layer protocols, representing a wide variety of applications, including network management, file transfer, distributed file services, terminal emulation, and electronic mail. Table 7-1 maps the best-known Internet upper-layer protocols to the applications they support. Table 7-1 Internet Protocol Application Mapping Table 7-1 Internet Protocol Application Mapping File Transfer Protocol (FTP) provides a way to move files between computer systems....

Using Extended ping Tests

The ping command is a useful test available on Cisco internetworking devices as well as on many host systems. In TCP IP, this diagnostic tool is also known as an Internet Control Message Protocol (ICMP) Echo Request. Note The ping command is particularly useful when high levels of input errors are being registered in the show interfaces serial display. See Figure 15-1. Cisco internetworking devices provide a mechanism to automate the sending of many ping packets in sequence. Figure 15-5...

Using the modem autoconfigure Command

If you are using Cisco Internetwork Operating System (Cisco IOS) Release 11.1 or later, you can configure your Cisco router to communicate with and configure your modem automatically. Use the following procedure to configure a Cisco router to automatically attempt to discover what kind of modem is connected to the line and then to configure the modem Step 1 To discover the type of modem attached to your router, use the modem autoconfigure discovery line configuration command. Step 2 When the...

Using the show controllers Command

The show controllers exec command is another important diagnostic tool when troubleshooting serial lines. The command syntax varies depending on platform For serial interfaces on Cisco 7000 series routers, use the show controllers cbus exec command For Cisco access products, use the show controllers exec command For the AGS, CGS, and MGS, use the show controllers mci exec command Figure 15-2 shows the output from the show controllers cbus exec command. This command is used on Cisco 7000 series...

VINES Client Cannot Connect to Server over PSN

Symptom Clients cannot connect to VINES servers across a packet-switched network (PSN). Clients can connect to local VINES servers. Table 13-2 outlines the problems that might cause this symptom and describes solutions to those problems. Table 13-2 VINES Client Cannot Connect to Server over PSN Table 13-2 VINES Client Cannot Connect to Server over PSN Step 1 Use the show running-config privileged exec command to view the configuration of the router. Step 2 For X.25 environments, make sure that...

VINES Clients Cannot Communicate with Servers over Router

Symptom Clients cannot connect to VINES servers over one or more routers. Clients might or might not be able to connect to servers on their directly connected networks. Table 13-1 outlines the problems that might cause this symptom and describes solutions to those problems. Table 13-1 VINES Clients Cannot Communicate with Servers over Router Table 13-1 VINES Clients Cannot Communicate with Servers over Router Step 1 Use the show interfaces exec command to check the status of the router...

Xns Xns Broadcast Packets Not Forwarded by Router

Symptom XNS servers do not respond to broadcast requests from clients. Table 14-2 outlines the problems that might cause this symptom and describes solutions to those problems. Table 14-2 XNS XNS Broadcast Packets Not Forwarded by Router Table 14-2 XNS XNS Broadcast Packets Not Forwarded by Router Caution Because debugging output is assigned high priority in the CPU process, it can render the system unusable. For this reason, use debug commands only to troubleshoot specific problems or during...

Addressing

As with all network-layer protocols, the addressing scheme is integral to the process of routing IP datagrams through an internetwork. An IP address is 32 bits in length, divided into either two or three parts. The first part designates the network address the second part (if present) designates the subnet address and the final part designates the host address. Subnet addresses are present only if the network administrator has decided that the network should be divided into subnetworks. The...

CSU and DSU Loopback Tests

If the output of the show interfaces serial exec command indicates that the serial line is up but the line protocol is down, use the CSU DSU loopback tests to determine the source of the problem. Perform the local loop test first, and then the remote test. Figure 15-9 illustrates the basic topology of the CSU DSU local and remote loopback tests. Figure 15-9 CSU DSU Local and Remote Loopback Tests Figure 15-9 CSU DSU Local and Remote Loopback Tests Note These tests are generic in nature and...

Show interfaces fddi

To display information about the FDDI interface, use the show interfaces fddi exec -command show interfaces fddi number accounting show interfaces fddi slot port accounting (Cisco 7000 series and Cisco 7200 series) show interfaces fddi slot port-adapter port accounting (Cisco 7500 series routers) number---Port number on the selected interface. accounting---(Optional) Displays the number of packets of each protocol type that have been sent through the interface. slot---Refers to the appropriate...

Serial Lines show interfaces serial Status Line Conditions

You can identify five possible problem states in the interface status line of the show interfaces serial display (see Figure 15-1) Serial x is down, line protocol is down Serial x is up, line protocol is down Serial x is up, line protocol is up (looped) Serial x is up, line protocol is down (disabled) Serial x is administratively down, line protocol is down Figure 15-1 Output of the HDLC show interface serial Command Table 15-1 shows the interface status conditions, possible problems associated...

Apple Talk Configuration and Troubleshooting Tips

This section offers configuration and troubleshooting tips that can help you prevent or more easily repair problems in AppleTalk internetworks. It consists of information on preventing AppleTalk problems, preventing internetwork reconfiguration problems, changing zone names, using AppleTalk Discovery Mode, and forcing an interface up to allow a router to start functioning if the network is misconfigured. Table 9-1 lists suggestions to help you avoid problems when configuring a router for...

Translational Bridging Client Cannot Connect to Server

Symptom Clients cannot communicate over a router configured as a translational bridge. Note In certain situations, replacing existing translational bridges with Cisco translational bridges can cause interoperability problems. Some translational bridge implementations map functional addresses between media (such as local-area transport LAT functional address 0900.2B00.00FA on Ethernet) to a broadcast address on the Token Ring side (such as C000.FFFF.FFFF). Cisco does not support this...

OSPF Routes Missing from Routing Table

Symptom OSPF routes and networks are not being advertised to other routers. Routers in one area are not receiving routing information for other areas. Some hosts cannot communicate with hosts in other areas, and routing table information is incomplete. Table 7-12 outlines the problems that might cause this symptom and describes solutions to those problems. Table 7-12 OSPF Routes Missing from Routing Table Table 7-12 OSPF Routes Missing from Routing Table Follow the procedures outlined in the...

IPX Enhanced Igrp Sap Updates Not Propagated by Router

Symptom Novell SAP packets are not forwarded through a router running IPX Enhanced IGRP. Clients might be unable to connect to servers over one or more routers, or they might connect only intermittently. Note Procedures for troubleshooting IPX Enhanced IGRP problems not specific to SAPs are described in the section IPX Enhanced IGRP No Connectivity over IPX Enhanced IGRP Router earlier in this chapter. Table 8-10 outlines the problems that might cause this symptom and describes solutions to...

Clocking Problem Solutions

Table 15-8 outlines suggested remedies for clocking problems, based on the source of the problem. Table 15-8 Serial Lines Clocking Problems and Solutions Table 15-8 Serial Lines Clocking Problems and Solutions Step 1 Determine whether the CSUs at both ends agree on the clock source (local or line). Step 2 If the CSUs do not agree, configure them so that they do (usually the line is the source). Step 3 Check the LBO1 setting on the CSU to ensure that the impedance matches that of the physical...

Show interfaces serial

To display information about a serial interface, use the show interfaces serial privileged exec command show interfaces serial number accounting show interfaces serial number channel-group accounting (Cisco 4000 series) show interfaces serial slot port channel-group accounting (Cisco 7500 series) show interfaces serial type slot port-adapter port serial (ports on VIP cards in the Cisco 7500 series) show interfaces serial type slot port-adapter port t1-channel accounting crb (CT3IP in Cisco 7500...

HSRP Hosts Cannot Reach Remote Networks

Symptom Hosts cannot reach hosts on remote networks. Routers in the network are running HSRP. Table 7-18 outlines the problems that might cause this symptom and describes solutions to those problems. Table 7-18 HSRP Hosts Cannot Reach Remote Networks Table 7-18 HSRP Hosts Cannot Reach Remote Networks Default gateway is not specified or is incorrectly specified on local or remote hosts Step 1 Determine whether local and remote hosts have a default gateway specification. Use the following UNIX...

Ipx Rip No Connectivity over Ipx Rip Router

Symptom IPX RIP routers are blocking connections. Clients cannot connect to servers over one or more routers running IPX RIP. Note Procedures for troubleshooting connectivity problems not specific to IPX RIP routing are described in the section Novell IPX Client Cannot Connect to Server on Remote LAN earlier in this chapter. Table 8-6 outlines the problems that might cause this symptom and describes solutions to those problems. Table 8-6 IPX RIP No Connectivity over IPX RIP Router Table 8-6 IPX...