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...

SDLC Intermittent Connectivity

Symptom User connections to hosts time out over a router configured to perform SDLC transport. Table 10-10 outlines the problem that might cause this symptom and describes solutions to that problem. Table 10-10 SDLC Intermittent Connectivity Table 10-10 SDLC Intermittent Connectivity Step 1 Place a serial analyzer on the serial line attached to the source station and monitor packets. Step 2 If duplicate packets appear, check the router configuration using the show running-config privileged exec...

SDLC Client Cannot Connect to Host over Router Running SDLLC

Symptom Users cannot open connections to hosts on the other side of a router configured to support SDLC Logical Link Control (SDLLC). Table 10-11 outlines the problems that might cause this symptom and describes solutions to those problems. Table 10-11 SDLC Client Cannot Connect to Host over Router Running SDLLC Table 10-11 SDLC Client Cannot Connect to Host over Router Running SDLLC SDLC physical or data link-layer problem Step 1 Use the show interface slot port exec command to check the state...

Network Analyzers

A network analyzer (also called a protocol analyzer) decodes the various protocol layers in a recorded frame and presents them as readable abbreviations or summaries, detailing which layer is involved (physical, data link, and so forth) and what function each byte or byte content serves. Most network analyzers can perform many of the following functions Filter traffic that meets certain criteria so that, for example, all traffic to and from a particular device can be captured Present protocol...

Ipx Rip Sap Updates Not Propagated by Router

Symptom Novell SAP packets are not forwarded through a router running IPX RIP. Clients might be unable to connect to servers over one or more routers, or they might intermittently be able to connect. Note Procedures for troubleshooting IPX RIP problems not specific to SAPs are described in the section IPX RIP No Connectivity over IPX RIP (12 of 30) 11 30 2000 11 15 42 PM Router earlier in this chapter. Additional problems relating to intermittent connectivity problems are described in the...

XNS Clients Cannot Connect to Servers over Router

Symptom Clients cannot make connections to XNS servers across a router. Clients might be able to connect to servers on their directly connected networks. Table 14-1 outlines the problems that might cause this symptom and describes solutions to those problems. Table 14-1 XNS Clients Cannot Connect to Servers over Router Table 14-1 XNS Clients Cannot Connect to Servers over Router Step 1 Use the show interfaces exec command to check the status of the router interfaces. Step 2 If the status line...

IP Enhanced IGRP Routes Missing from Routing Table

Symptom Routes are missing from the routing table of routers running Enhanced IGRP. Hosts on one network cannot access hosts on a different network. Hosts on the same network might or might not be able to communicate. The problem might occur in internetworks running only Enhanced IGRP or in an internetwork running Enhanced IGRP and another routing protocol. Table 7-14 outlines the problems that might cause this symptom and describes solutions to those problems. Table 7-14 IP Enhanced IGRP...

TCPIP Routes Learned from the Wrong Interface or Protocol

Symptom Routes in the routing table were learned from the wrong interface or protocol. For example, networks that should be reached through one interface are shown in the routing table to be reachable through another interface instead. This problem occurs only in a multiprotocol environment (see the section 'Split Horizon Example, later in this chapter). Table 7-4 outlines the problems that might cause this symptom and describes solutions to those problems. Table 7-4 TCP IP Routes Learned from...

Novell SAPs

The list of Novell SAPs in Table 8-14 is unverified information contributed from various sources. Novell, in an official capacity, does not and has not provided any of this information. Table 8-14 Novell SAPs, Their Descriptions, and Their Decimal and Hex Values Table 8-14 Novell SAPs, Their Descriptions, and Their Decimal and Hex Values NACS Async Gateway or Asynchronous Gateway Bridge Server or Asynchronous Bridge Server Point to Point (Eicon) X.25 Bridge Server Time Synchronization Server or...

Interpreting show line Output

The output from the show line line-number exec command is useful when troubleshooting a modem-to-access server or router connection. Figure 16-2 shows the output from the show line command. Figure 16-2 show line Command Output When connectivity problems occur, important output appears in the Modem state and the Modem hardware state fields. Note The Modem hardware state field does not appear in the show line output for every platform. In certain cases, the indications for signal states will be...

VINES Client on Serverless Network Cannot Connect to Server over PSN

Symptom Clients on a serverless network (that is, a network segment that has no attached VINES servers) cannot open a connection to a VINES server over a PSN. Table 13-3 outlines the problems that might cause this symptom and describes solutions to those problems. Table 13-3 VINES Client on Serverless Network Cannot Connect to Server over PSN Table 13-3 VINES Client on Serverless Network Cannot Connect to Server over PSN Step 1 Use the show running-config privileged exec command to view the...

Iso Clns Technology Basics

The world of OSI networking has a unique terminology End system (ES) refers to any nonrouting network device. Intermediate system (IS) refers to a router. Area is a group of contiguous networks and attached hosts that are specified by a network administrator or manager to be an area. Domain is a collection of connected areas. Routing domains provide full connectivity to all end systems within them. Addresses in the ISO network architecture are referred to as NSAP addresses and network entity...

IPX Enhanced IGRP Router Stuck in Active Mode

Symptom An IPX Enhanced IGRP router is stuck in Active mode. The router repeatedly sends error messages similar to the following DUAL-3-SIA Route 3c.0800.0c00.4321 Stuck-in-Active 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 these error messages occur frequently, you should investigate the problem. For a more detailed explanation of Enhanced IGRP...

Establishing a Reverse Telnet Session to a Modem

If you are running Cisco IOS Release 11.0 or earlier, you must establish a reverse Telnet session to configure a modem to communicate with a Cisco device. As long as you lock the data terminal equipment (DTE)-side speed of the modem (see Table 16-5 for information on locking the modem speed), the modem will always communicate with the access server or router at the desired speed. Be certain that the speed of the Cisco device is configured prior to issuing commands to the modem via a reverse...

Apple Talk Enhanced IGRP Router Stuck in Active Mode

Symptom An AppleTalk Enhanced IGRP router is stuck in Active mode. The router repeatedly sends error messages similar to the following to the console DUAL-3-SIA Route 2.24 Stuck-in-Active 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 these error messages occur frequently, you should investigate the problem. For a more detailed explanation of...

Ripigrp Routes Missing from Routing Table

Symptom Routes are missing from the routing table. Hosts on one network cannot access hosts on a different network. Error messages stating host or destination unreachable are generated. The problem might be occurring in an internetwork running only RIP or IGRP, or a combination of the two. Table 7-9 outlines the problems that might cause this symptom and describes solutions to those problems. Table 7-9 RIP IGRP Routes Missing from Routing Table Table 7-9 RIP IGRP Routes Missing from Routing...

Troubleshooting Iso Clns

This section presents protocol-related troubleshooting information for ISO CLNS protocol connectivity and performance problems. It describes specific ISO CLNS symptoms, the problems that are likely to cause each symptom, and the solutions to those problems. Note Discussions of host configuration problems in this chapter assume that the host is a UNIX system. Equivalent actions might also be applicable to non-UNIX hosts, but the discussions do not specifically address non-UNIX end-station...

Adobe Acrobat Reader

In order to view the scalable Portable Document Format (PDF) versions of graphics and tables on Cisco Connection Documentation CD-ROM, you need to have Adobe Acrobat Reader configured as a helper application of Verity Mosaic. The Adobe Acrobat Reader installer is copied to the same location as the Cisco Connection Documentation CD-ROM applications on the Macintosh, Windows, SunOS, and Solaris platforms when you install Cisco Connection Documentation CD-ROM. Run the Adobe Acrobat Reader...

TCPIP Problems Forwarding BOOTP and Other UDP Broadcasts

Symptom Problems occur when forwarding BOOTP or other UDP broadcast packets. UDP broadcasts sent from network hosts are not forwarded by routers. Diskless workstations cannot boot. Table 7-7 outlines the problems that might cause this symptom and describes solutions to those problems. Table 7-7 TCP IP Problems Forwarding BOOTP and Other UDP Broadcasts Figure 7-12 A Misconfigured Access List Sample Network Missing or misconfigured ip helper-address Step 1 Use the debug ip udp privileged exec...