Access Layer Switches

Recall that access layer devices should have these features High port density to connect to end users Uplinks to higher layers of the campus network Layer 2 services (traffic filtering and VLAN membership) For small campus networks, the Catalyst 1900 or 2820 series switches can be used as access layer devices. Their smaller port densities can connect 10BaseT users and hubs, while connecting to distribution layer switches with 100BaseX uplinks. The Catalyst 2900XL and 3500XL switches are useful...

Additional InterVLAN Routing Configurations

Once a route processor has been configured for interVLAN routing, end-user stations can use the processor. Normally, an end-user device knows only about its local subnet and can communicate only with stations on the local network or VLAN. To reach another station on a different VLAN, packets must be forwarded to a router. Therefore, each end-user device should be configured with the router's IP address on the local VLAN. This configuration is known as a default gateway. In addition, a switch...

Address Resolution Scenario 1 Using Ip Arp to Resolve MAC Addresses

Workstation A needs to contact Workstation B, but only knows its IP address. IP ARP is used to find Workstation B's MAC address Step 1 A workstation generates an ARP request broadcast on its local LAN (switch port) to find a MAC address. Step 2 The switch floods the broadcast out all VLAN ports, as well as to the ELAN associated with the VLAN. This flooding occurs on the switch's ATM module. Step 3 The LEC contacts the BUS with a broadcast frame to be delivered. Step 4 The BUS sends the...

Anatomy of an HSRP Message

All routers in a standby group send or receive HSRP messages. These messages are used to determine and maintain the router roles within the group. HSRP messages are encapsulated in the data portion of User Datagram Protocol (UDP) packets and use port number 1985. These packets are addressed to an all router multicast address with a Time to Live (TTL) of one (1). Figure 9-5 shows the general format for an HSRP message. Anatomy of an HSRP Message 1 Octet 1 Octet 1 Octet 1 Octet The HSRP message...

Answers to Chapter 10 Do I Know This Already Quiz

1 Name the three types of traffic available in today's multimedia environment Unicast traffic, broadcast traffic, and multicast traffic. 2 What Layer 4protocol is used to carry multicast traffic The transport layer protocol UDP is used to carry multicast traffic. UDP is a simpler, more efficient protocol because there is no flow control, reliability, or error recovery added to IP. 3 What Class of IP address is used in a multicast environment IP multicast is Class D. 4 Describe the makeup of the...

Answers to Chapter 11 QA Section

1 Which Internet Request for Comment (RFC) deals with multicasts RFC 1112 is titled Host Extensions for IP Multicasting and was the original specification. RFC 2236, titled Internet Group Management Protocol, Version 2, is the most recent. 2 What is the name of the industry standard protocol that deals with multicast groups The Cisco proprietary protocol IGMP is the industry standard, and CGMP is the Cisco proprietary protocol. 3 What command enables multicast routing on a Cisco router At the...

Answers to Chapter 12 QA Section

A policy is a firm's documented standard of network access for their users. 2 What is the access layer defined as The access layer is defined at the point at which a user enters the network. 3 Is HTTP access normally enabled on a Cisco router What is the main purpose of using HTTP HTTP access is normally disabled on a Cisco router. The main purpose of using it is to make configuration easier. 4 Name at least two components relating to controlling access to network devices. Physical security,...

Answers to Chapter 13 Do I Know This Already Quiz

1 What is the main method of out-of-band management for Cisco switches The main method of out-of-band management is the console connection. 2 What is an application that uses SNMP to perform in-band management CiscoWorks 2000. 3 CDP operates at what layer of the OSI model CDP operates at the data link layer. 4 What is the command to verify that RMON is enabled on the switch show snmp 5 Using a troubleshooting model, what step is generally taken after ascertaining all the facts 6 What is the...

Answers to Chapter 2 Do I Know This Already Quiz

1 Describe the differences between Layer 2, Layer 3, and Layer 4 switching. In Layer 2 switching, frames are forwarded based on the Layer 2 source and destination MAC addresses. In Layer 3 switching, network layer source and destination addresses (IP, IPX, and so forth) are used. In Layer 4 switching, some application information is taken into account along with Layer 3 addresses. For IP, this information includes the port numbers from such protocol types as UDP and TCP. 2 What is multilayer...

Answers to Chapter 2 QA Section

1 Where is the most appropriate place to connect a block of enterprise servers Why A block of enterprise servers should be connected into the core, just as switch blocks are. This maximizes connectivity from the servers to all other devices in the network. In effect, all users will see the same number of switch hops to access a server. Connecting into the core also provides maximum scalability as more server blocks can be added in the future. 2 Describe the differences between Layer 2, Layer 3,...

Answers to Chapter 3 Do I Know This Already Quiz

1 What are the different Ethernet technologies and their associated IEEE standards Ethernet (10 Mbps, IEEE 802.3), Fast Ethernet (100 Mbps, IEEE 802.3u), and Gigabit Ethernet (1000 Mbps, IEEE 802.3z) 2 What benefits result with switched Ethernet over shared Ethernet Switched Ethernet ports receive dedicated bandwidth, have a reduced collision domain, and have increased performance due to segmentation or fewer users per port. 3 At what layer are traditional 10 Mbps Ethernet, Fast Ethernet, and...

Answers to Chapter 3 QA Section

1 What are the different Ethernet technologies and their associated IEEE standards Ethernet (10 Mbps, IEEE 802.3), Fast Ethernet (100 Mbps, IEEE 802.3u), and Gigabit Ethernet (1000 Mbps, IEEE 802.3z) 2 What benefits result with switched Ethernet over shared Ethernet Switched Ethernet ports receive dedicated bandwidth, have a reduced collision domain, and have an increased performance due to segmentation or fewer users per port. 3 When a 10 100 Ethernet link is autonegotiating, which will be...

Answers to Chapter 4 Do I Know This Already Quiz

1 What is a VLAN When is it used A VLAN is a group of devices on the same broadcast domain, as a logical subnet or segment. VLANs can span switch ports, switches within a switch block, or closets and buildings. VLANs are used to group users and devices into common workgroups across geographical areas. VLANs help provide segmentation, security, and problem isolation. 2 What are two types of VLANs, in terms of spanning areas of the campus network End-to-end (spans entire campus network) and local...

Answers to Chapter 4 QA Section

1 What is a VLAN When is it used A VLAN is a group of devices on the same broadcast domain, as a logical subnet or segment. VLANs can span switch ports, switches within a switch block, or closets and buildings. VLANs are used to group users and devices into common workgroups across geographical areas. VLANs help provide segmentation, security, and problem isolation. 2 When a VLAN is configured on a Catalyst switch port, in how much of the campus network will the VLAN number be unique and...

Answers to Chapter 5 Do I Know This Already Quiz

1 What is EtherChannel What types of switch links can it be used with EtherChannel is a method for aggregating multiple physical Ethernet ports into a single logical link. EtherChannel can be used with full-duplex Fast Ethernet or Gigabit Ethernet links. 2 How is traffic distributed over an EtherChannel Traffic is distributed according to addresses contained in frames passing through the switch not according to port loads or equal distribution across the individual ports in a bundle. Switches...

Answers to Chapter 6 Do I Know This Already Quiz

1 What is the basic unit of ATM data What is its basic format (header, payload, and so forth) The basic ATM data unit is the cell. An ATM cell consists of a 5-byte header and a 48-byte payload. 2 What is an ATM edge device What Cisco devices can be used An ATM edge device interfaces native ATM to other media. For example, Cisco Catalyst switches (5000 and 6000) can be used to bridge between LAN ports and an ATM LANE module. Also, Cisco routers (4500 4700, 7500, for example) can bridge between...

Answers to Chapter 7 Do I Know This Already Quiz

1 Where can a router be placed in relation to switches for interVLAN routing External to the switches or internal (integrated) to a switch. 2 What types of links can be used to interconnect switches and an external router How many VLANs can be carried on each Links can be used with one VLAN per physical link, using any supported media. Trunk links can also be used to carry multiple VLANs over a single link, using such media as Fast Ethernet, Gigabit Ethernet, ATM LANE, and FDDI. 3 What trunking...

Answers to Chapter 8 Do I Know This Already Quiz

1 What devices make up the basis for Layer 3 switching as it relates in a Cisco environment Catalyst switches 2 What device is the definition of a Multilayer Switch Engine (MLS-SE) The Multilayer Switch Engine is a Supervisor III card in a Catalyst switch with a Netflow Feature Card (NFFC) enabled on it. On a Catalyst 6000, the PFC MSFC combination can also perform MLS. 3 What devices can be used as a Multilayer Switch Route Processor (MLS-RP) A Route Switch Module (RSM) and any Cisco router...

Answers to Chapter 8 QA Section

1 What devices are the basis for Layer 3 switching as it relates in a Cisco environment Catalyst switches. 2 What device is the definition of a Multilayer Switch Engine (MLS-SE) The Multilayer Switch Engine is a Supervisor III card in a Catalyst switch with a Netflow Feature Card (NFFC) enabled on it. 3 What devices can be used as a Multilayer Switch Route Processor (MLS-RP) A Route Switch Module (RSM) or any Cisco router that supports MLS in software (Typically, a 75xx, 72xx, 45xx, 47xx, or...

Answers to Chapter 9 Do I Know This Already Quiz

1 What is the name of the protocol that allows a set of routers that are working together to form one virtual-router Hot Standby Router Protocol or HSRP. 2 What is the minimum number of routers needed to perform HSRP The minimum number of routers needed is at least two. One functions as an active router and one as a standby. 3 In a properly functioning virtual router, what happens when the active router fails In a properly functioning HSRP environment, packets will still be routed in the event...

Answers to Chapter 9 QA Section

1 What is the name of the protocol that allows a set of routers that are working together to form one virtual router Hot Standby router Protocol or HSRP. 2 What problem makes HSRP necessary The fact that there isn't a dynamic protocol to discover new default gateways for hosts in the event of failure. 3 What is the minimum number of routers needed to perform HSRP The minimum number of routers needed is at least two. One functions as an active router and one as a standby. 4 What is the RFC that...

Backbone Fast Redundant Backbone Paths

In the network backbone, or Core layer, a different method is used to shorten STP convergence. BackboneFast works by having a switch actively determine if alternate paths exist to the root bridge in the event that the switch detects an indirect link failure. Indirect link failures occur when a link not directly connected to a switch fails. A switch detects an indirect link failure when it receives inferior BPDUs from its Designated Bridge on either its root port or a blocked port. (Inferior...

Breakout Boxes Fox Boxes and BERTsBLERTs

Breakout boxes, fox boxes, and bit block error rate testers are digital interface testing tools used to measure the digital signals present at PCs, printers, modems, CSU DSUs, and other peripheral interfaces. These devices can monitor data line conditions, analyze and trap data, and diagnose problems common to data communication systems. Traffic from data terminal equipment (DTE) through data communications equipment (DCE) can be examined to help isolate problems, identify bit patterns, and...

Bridging Loops

Recall that a Layer 2 switch mimics the function of a transparent bridge. A transparent bridge must offer segmentation between two networks, while remaining transparent to all the end devices connected to it. For the purpose of this discussion, consider a two-port Ethernet switch and its similarities to a two-port transparent bridge. A transparent bridge (and the Ethernet switch) must operate as follows The bridge has no initial knowledge of the location of any end device therefore, the bridge...

Broadcast Traffic

In a broadcast design, an application sends only one copy of each packet using a broadcast address. If this technique is used, however, broadcasts either must be stopped at the broadcast domain boundary with a Layer 3 device or transmitted to all devices in the campus network. Broadcasting a packet to all devices can be inefficient if only a small group in the network actually needs to see the packet as demonstrated in Figure 10-3. Broadcast multimedia is dispersed throughout the network just...

Bundling Ports with Ether Channel

Fast EtherChannel is available on the Catalyst 1900, 2820, 2900, 2900XL, 3500XL, 4000, 5000, and 6000 families. Gigabit EtherChannel is supported only on the Catalyst 2900, 2900XL, 4000, 5000, and 6000 families. Most of the switch families support a maximum of four FE or GE links bundled in a single EtherChannel link. However, the Catalyst 6000 family supports up to eight bundled links for a total throughput of 1600 Mbps (FEC) or 16 Gbps (GEC). The Catalyst 6000 also supports up to 128...

Cells and SAR

All types of traffic are transported over ATM as small cells. Using cells of an optimal fixed size allows the following benefits Low latency, high throughput Small cells can be moved very quickly from switch to switch with a low propagation delay for the short serialized data from each cell. Fixed-size cells then can be relayed at a predictable rate. ATM switches also use hardware-based switching and reduced addressing and decision spaces to speed cell relay. Multiservice traffic Traffic from...

Cisco Discovery Protocol CDP

Cisco Discovery Protocol (CDP) is media- and protocol-independent and runs on all Cisco-manufactured equipment including routers, bridges, access and communication servers, and switches. With CDP, network management applications can retrieve the device type and the SNMP-agent address of neighboring devices (see Figure 13-5). Applications are now enabled to send SNMP queries to neighboring devices. Figure 13-5 A Typical Cisco Network Environment with CDP Enabled Figure 13-5 A Typical Cisco...

Collapsed Core

A collapsed core block is one where the core layer of the hierarchy is collapsed into the distribution layer. Here, both distribution and core functions are provided within the same switch devices. This situation is usually found in smaller campus networks, where a separate core layer (and additional cost or performance) is not warranted. Figure 2-9 shows the basic collapsed core design. Although the distribution and core layer functions are performed in the same device, keeping these functions...

Common Spanning Tree CST

The IEEE 802.1Q standard specifies how VLANs are to be trunked between switches. As well, it specifies only a single instance of STP for all VLANs. This instance is referred to as the Common Spanning Tree (CST) or the Mono Spanning Tree (MST). All BPDUs are transmitted over VLAN 1, the management VLAN. Having a single STP for many VLANs simplifies switch configuration and reduces switch CPU load during STP calculations. However, the STP can cause limitations, too. Redundant links between...

Configure Routing Processes

Once connectivity has been configured between the switch and a route processor, you must also configure routing. Routes are paths to distant networks known on the local route processor, along with metrics for path costs and the addresses of next-hop route processors. In this fashion, a router hands off packets destined for a remote network to a neighboring router who is closer to the destination. Routers are used by end-user devices when the destination is not attached to the local network...

Configuring a Rendezvous Point

One of the features that you have to configure if you use PIM in sparse mode is a Rendezvous Point (RP). The routers learn that they are RPs automatically. RPs are used by multicast senders in a sparse mode environment to announce their existence. Through the destination, receivers learn about new senders. Multi-RP environments can be configured for any given multicast group. One term used in the description of RPs is leaf routers. Leaf routers are either directly connected to a multicast group...

Configuring a VTP Management Domain

Before a switch is added into a network, the VTP management domain should be identified. If this switch is the first one on the network, the management domain will need to be created. Otherwise, the switch may have to join an existing management domain with other existing switches. Configuring a VTP Management Domain on an IOS-Based Switch The following command can be used to assign a switch to a management domain, where the domain-name is a text string up to 32 characters long. Switch(vlan)...

Configuring CGMP Leave

In some cases, you may want multicast group to be removed from the forwarding tables, freeing up bandwidth. The command to accomplish this, called CGMP leave, is as follows A multicast router sends out group queries periodically. In a normal participating mode, the multicast hosts would send a reply to these queries. If, after a given number of queries no response is given by any members of a group, that group is then eligible to be pruned from the forwarding tables of the switch.

Configuring HSRP Standby Preempt

The standby router automatically assumes the active router role when the active router fails or is removed from service. This new active router remains the forwarding router even when the former active router with the higher priority regains service in the network. The former active router can be configured to resume the forwarding router role from a router with a lower priority. To enable a router to resume the forwarding router role, enter the following command in interface configuration mode...

Configuring HSRP Standby Priority

Each standby group has its own active and standby routers. The network administrator can assign a priority value to each router in a standby group, allowing the administrator to control the order in which active routers for that group are selected. To set the priority value of a router, enter the following command in interface configuration mode Router (config-if) standby group-number priority priority-value where group-number indicates the HSRP standby group. This number can be in the range of...

Configuring HSRP Tracking

To configure HSRP tracking, enter the following command in interface configuration mode Router(config-if) standby group-number track type-number interface-priority The command arguments for this command are defined as follows group-number This optional argument indicates the group number on the interface to which the tracking applies. The default number is 0. type This argument indicates the interface type (combined with the interface number) to be tracked. number This argument indicates the...

Configuring Internet Group Management Protocol IGMP

Internet Group Management Protocol (IGMP) is an important part of IP that must be supported by all multicast hosts on a network. Multicast routers use IGMP to keep track of multicast hosts on a network. Although two versions of IGMP are available, version 1 and version 2, IGMP version 2 is the default in all Cisco routers running IOS Release 11.3(2)T and later. To configure the multicast router to join a particular multicast group, enter the following command in the relevant interface...

Configuring IP Multicast

IP multicast and the task configuring it are somewhat advanced topics. Fortunately, the material on the CCNP Switching exam covers only the basics of configuring IP multicast. We will do the same here, but will list as optional a few of the advanced tasks. The two basic tasks in enabling multicast are Enabling IP multicast routing Enabling PIM on an interface Advanced tasks are optional and include the following Configuring a rendezvous point Configuring the Time To Live (TTL) threshold...

Configuring Multilayer Switching

The basic tasks for configuring multilayer switching include the following 2 Assigning a VLAN ID to a route processor interface. 3 Adding the interfaces to the same VLAN Trunking Protocol (VTP) domain as the switch. 4 Enabling MLS on every interface. 5 Configuring the MLS Management interface. Before you can configure MLS for a specific VLAN or interface, you must globally enable the MLSP that operates between the route processor and the switch. To enable MLSP on the route processor, enter the...

Configuring the LECS

The LECS is configured on a major ATM interface, not on a subinterface. First you must build the LECS database of ELANs and their associated LES NSAP addresses. Configure the LECS database with the following commands ATM(Config) lane database database-name ATM(lane-config-database) name elan1-name server-atm-address les1-nsap-address ATM(lane-config-database) name elan2-name server-atm-address les2-nsap-address ATM(lane-config-database) name The database-name argument is a text string that...

Console Port Connection

The console port is the local (out-of-band) console terminal connection to the switch a DB-25 female connector shown in Figure 13-2. Other switches may require different console cables in conjunction with modular plugs instead of the DB-25. Figure 13-2 The Catalyst 5000 Console Port Figure 13-2 The Catalyst 5000 Console Port To use the console port, connect via a straight-through cable, an EIA TIA-232 terminal (configured for 9600 baud, no parity, eight data bits, and one stop bit), modem, or...

Contents at a Glance

Chapter 1 All About the Cisco Certified Network Professional and Design Professional Certification 3 Chapter 2 Campus Network Design Models 15 Chapter 3 Basic Switch and Port Configuration 65 Chapter 4 VLANs and Trunking 97 Chapter 5 Redundant Switch Links 145 Chapter 6 Trunking with ATM LANE 203 Chapter 7 InterVLAN Routing 241 Chapter 8 Multilayer Switching 265 Chapter 9 Overview of Hot Standby Routing Protocol 301 Chapter 11 Configuring Multicast Networks 369 Chapter 12 Controlling Access in...

Controlling Routing Update Traffic

Controlling the routing table of the core block has several advantages Reduces the size of the routing table at the core block allowing it to process packets faster. Prevents users from getting to networks that have not been advertised unless they have a static or default route to get there. Prevents incorrect information from propagating through the core block. Two methods are available for controlling the routing information that is sent to the core block, as follows Route summarization...

Core Layer Policy

The core block is responsible for moving data quickly. All the devices that are designed to be core block solutions are optimized to move data as quickly as possible. For this reason, the core block should have little to no policy. The only policies that should be applied at the core block are those that relate to quality of service (QoS) commands for congestion management and congestion avoidance. QoS implementations vary, depending on hardware used and versions of IOS. Please see your...

Debugging Multicast

Many potential commands can be used when debugging multicast. We will go over a couple of the most important here. You can find documentation on other debugging commands at CCO (www.cisco.com). The first command of significance, show ip pim neighbor, displays the PIM neighbor table as demonstrated earlier in Example 11-1. Another relevant command, show ip mroute, shows the entries in the multicast routing table. The general syntax for this command is as follows DallasR1> show ip mroute...

Dense Mode Routing Protocols

The first method for multicast routing is based on the assumption that the multicast group members are densely distributed throughout the network and bandwidth is plentiful, meaning that almost all hosts on the network belong to the group. These dense mode multicast routing protocols rely on periodic flooding of the network with multicast traffic to set up and maintain the distribution tree. Dense mode routing protocols include the following Distance Vector Multicast Routing Protocol (DVMRP)...

Displaying MLS Cache Entries

To display the MLS cache entries, enter the following command in privilege EXEC mode This command might be used as a troubleshooting tool or just to check the status of a particular flow that you're interested in. This command can be further defined to show MLS cache entries for the parameters defined in Table 8-2. To remove entries from the MLS cache, enter the clear mls entry command in privilege EXEC mode. Table 8-3 lists how to remove MLS cache entries based on given criteria. Table 8-2...

Displaying VTP Domain Information

Sometimes seeing VTP domain information is useful. The show mls rp vtp-domain command allows you to see domain information for a specific VTP domain Router show mls rp vtp-domain vtp domain name The display resulting from this command (see Example 8-4) shows a subset of the show mls rp command display. The following information is a result of issuing the show mls rp vtp-domain command The name of the VTP domain(s) in which the MLS-RP interfaces reside. Statistical information for each VTP...

Distribution Layer Switches

Switches used in the distribution layer should offer these features Aggregation of access layer devices High Layer 3 throughput InterVLAN routing Robust Layer 3 functionality In the distribution layer, uplinks from all access layer devices are aggregated, or come together. Therefore, the distribution layer switches must be capable of processing the total volume of traffic from all the connected devices. These switches should have a port density of high-speed links to support the collection of...

Distribution Trees

For efficient transmission of multicast traffic, designated routers construct a tree that connects all members of an IP multicast group. A distribution tree specifies a unique forwarding path between the subnet of the source and each subnet containing members of the multicast group. A distribution tree has just enough connectivity so that there is only one loop-free path between every pair of routers. Because each router knows which of its lines belong to the tree, the router can copy an...

Do I Know This Already Quiz

The purpose of the Do I Know This Already quiz is to help you decide which parts of this chapter to use. If you already intend to read the entire chapter, you do not necessarily need to answer these questions now. The quiz helps you make good choices of how to spend your limited study time. The quiz is sectioned into five smaller quizlets, which correspond to the five major headings in the Foundation Topics section of the chapter. Although your answer may differ somewhat from the answers given,...

Dynamic Trunking Protocol

Trunk links on Catalyst switches can be manually configured for either ISL or 802.1Q mode. However, Cisco has implemented a proprietary point-to-point protocol called Dynamic Trunking Protocol (DTP) that will negotiate a common trunking mode between two switches. DTP is available in Catalyst supervisor engine software Release 4.2 and later. DTP negotiation should be disabled if a switch has a trunk link connected to a router because the router cannot participate in the DTP negotiation protocol....

Electing a Root Bridge

For all switches in a network to agree on a loop-free topology, a common frame of reference must exist to use as a guide. This reference point is called the Root Bridge. (The term bridge continues to be used even in a switched environment because STP was developed for use in bridges. Therefore, when you see bridge, think switch.) The Root Bridge is chosen by an election process among all connected switches. Each switch has a unique Bridge ID that it uses to identify itself to other switches....

Electing Designated Ports

By now, you should begin to see the process unfolding a starting or reference point has been identified, and each switch connects itself toward the reference point with the closest single link. A tree structure is beginning to emerge, but links have only been identified at this point. All links are still connected and could be active, leaving bridging loops. To remove the possibility of bridging loops, STP makes a final computation to identify one Designated Port on each network segment....

Electing Root Ports

Now that a reference point has been nominated and elected for the entire switched network, each non-root switch must figure out where it is in relation to the Root Bridge. This action can be performed by selecting only one Root Port on each non-root switch. STP uses the concept of cost to determine many things. Selecting a Root Port involves evaluating the Root Path Cost. This value is the cumulative cost of all the links leading to the Root Bridge. A particular switch link has a cost...

Enabling and Verifying Port Security Using the set CLI on set Command Based Switches

Use the following commands to enable and verify port security on a set command-based switch Switch (enable) set port security mod_num port_num enable mac address Switch (enable) show port mod_num port_num For example, consider the setup in Figure 12-5. Figure 12-5 Enabling and Verifying Port Security Example 12-8 demonstrates how to enable and then verify port security for the set command-based switch in Figure 12-5. Example 12-8 Enabling Verifying Port Security on a set Command-Based Switch...

Enabling CDP and Viewing CDP Information on an IOSBased Switch

CDP is enabled by default on all switch interfaces. To enable CDP, use the following interface configuration command (use the no form to disable CDP) Switch(config-if) cdp enable Switch(config-if) no cdp enable To view information learned from CDP advertisements of neighboring Cisco devices, use one of the following commands Switch show cdp interface type module port Switch show cdp neighbors type module port detail The first command displays CDP information pertaining to a specific interface....

Enabling PIM on an Interface

When you enable multicast routing on a route processor or router, it is processed on an individual interface basis. Enabling each individual interface used with a specific multicast routing protocol is necessary. The command to enable PIM on an interface is DallasR1> (config-if) ip pim dense-mode sparse-mode sparse-dense-mode The options for this command are defined as follows. dense-mode Enables dense mode of operation. Dense mode is used when all routers in the network will need to...

Enabling VTP Pruning on a CLIBased Switch

VTP pruning is enabled using the set vtp pruning enable command. If this command is used on a VTP server, pruning is enabled for the entire management domain. By default, VTP pruning is disabled. When pruning is enabled with this command, all VLANs become eligible for pruning on all trunk links, if needed. The default list of pruning eligibility can be modified. Like VLAN trunking, you can first clear VLANs from the eligibility list using the clear vtp pruneeligible vlan-range command. Then,...

Ether Channel Configuration

Before configuring switch ports into an EtherChannel bundle, you should make sure the switch module supports it. Use the show port capabilities module port command to do this. (This command is available on Catalyst software versions 4.x and later.) Example 5-1 demonstrates using the show port capabilities command to ensure the switch module supports EtherChannel bundling. Example 5-1 show port capabilities Command Output On this and other early Ethernet modules, only certain ports can be...

Extent of VLANs

To implement VLANs, you must give some consideration to the number of VLANs you'll need and how best to place them. As usual, the number of VLANs will be dependent on traffic patterns, application types, segmenting common workgroups, and network management requirements. However, an important factor to consider is the relationship between VLANs and the IP addressing schemes used. Cisco recommends a one-to-one correspondence between VLANs and IP subnets. This recommendation means that if a Class...

External Router Support

If the switch supports an externally attached MLS-RP, the switch must be manually configured to recognize that MLS-RP. To manually include an external MLS-RP, enter the following command in privilege EXEC mode on the switch Switch (enable) set mls include ip-addr where ip-addr is the MLS IP address of the external router. To determine the IP address of the MLS-RP, enter the show mls rp command on the MLS-RP. Perform this command only for external routers. The MLS-SE automatically includes the...

Flow Masks

The MLS-SE uses flow mask modes to determine how packets are compared to MLS entries in the MLS cache. The flow mask mode is based on the access lists configured on the MLS router interfaces. The MLS-SE learns the flow mask through MLSP messages from each MLS-RP for which the MLS-SE is performing Layer 3 switching. MLS-SE supports only one flow mask for all MLS-RPs that are serviced by the MLS-SE. If the MLS-SE detects different flow masks from different MLS-RPs for which the MLS-SE is...

Foundation Summary

The Foundation Summary is a collection of tables and figures that provides a convenient review of many key concepts in this chapter. For those of you already comfortable with the topics in this chapter, this summary could help you recall a few details. For those of you who just read this chapter, this review should help solidify some key facts. For any of you doing your final preparation before the exam, the following tables and figures will hopefully be a convenient way to review the day...

Foundation Topics Access Policies

Access policies are the defining guidelines that are necessary to create a level of access control. An access policy is a firm's documented standard of network access for the firm's users. Access policies may vary widely just like the business itself. Different size businesses may require a different type of access policy. In general, a corporate network security policy, whether or not it covers access, is designed to protect to the level of the data it is securing. An access policy may define...

Foundation Topics ATM Review

This section presents a brief review of ATM concepts and operation. Although it is not necessary to know the intimate details of ATM, how to configure an ATM switch, or how the underlying ATM protocols work, you should understand ATM well enough to effectively design and configure LANE. ATM is designed to provide multiple service types (voice, video, and data) over single pipelines very efficiently. All traffic is transported as small fixed-size cells. As well, traffic is not moved based on...

Foundation Topics InterVLAN Routing Background

Several chapters have dealt with the foundations of network design, VLANs, and trunking. However, VLANs have been presented as isolated broadcast domains. The next two chapters discuss how to transport traffic between VLANs using Layer 3 functions. VLANs are typically configured on Layer 2 switches to form broadcast domains. VLANs can exist in one or more switches through the use of trunking. As well, VLANs usually represent subnetworks of Layer 3 protocols. Since Layer 2 switches do not use...

Foundation Topics Monitoring Cisco Switches

You can monitor and manage your Catalyst switches in a number of different ways. One way is primarily through a console port using either the command-line interface (CLI) or other methods for performing network management functions, such as Cisco Discovery Protocol (CDP), Embedded Remote Monitoring (RMON), or Switched Port Analyzer (SPAN). The console port is an EIA TIA-232 DCE interface to which you can connect a console terminal or modem. The type of connector, however, used depends on the...

Foundation Topics Switch Port Aggregation with Ether Channel

As discussed in Chapter 3, Basic Switch and Port Configuration, switches can use Ethernet, Fast Ethernet, or Gigabit Ethernet ports to scale link speeds by a factor of ten. Cisco offers another method of scaling link bandwidth by aggregating or bundling parallel links, termed the EtherChannel technology. Two to eight links of either Fast Ethernet (FE) or Gigabit Ethernet (GE) are bundled as one logical link of Fast EtherChannel (FEC) or Gigabit EtherChannel (GEC), respectively. This bundle...

Foundation Topics Switching Functionality

To understand how switches and routers should be chosen and placed in a network design, you should first understand how to take advantage of data communication at different layers. The OSI model separates data communication into seven layers, as shown in Table 2-2. Each layer has a specific function and a specific protocol so that two devices can exchange data on the same layer. A protocol data unit (PDU) is the generic name for a block of data that a layer on one device exchanges with the same...

Foundation Topics Virtual LANs

Consider a network design that consists of Layer 2 devices only. For example, this design could be a single Ethernet segment, an Ethernet switch with many ports, or a network with several interconnected Ethernet switches. A fully Layer 2 switched network is referred to as a flat network topology. A flat network is a single broadcast domain, such that every connected device sees every broadcast packet that is transmitted. As the number of stations on the network increases, so does the number of...

General Troubleshooting 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 13-7 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...

Gigabit Ethernet

Fast Ethernet can be scaled by an additional order of magnitude with the use of Gigabit Ethernet (which supports 1,000 Mbps or 1 Gbps) using the same IEEE 802.3 Ethernet frame format as before. This scalability allows network designers and managers to leverage existing knowledge and technologies to install, migrate, manage, and maintain Gigabit Ethernet networks. However, the physical layer has been modified to increase data transmission speeds. Two technologies were merged together to gain the...

Gigabit Ethernet Port Cables Connectors

Gigabit Ethernet connections take a different approach by providing modular connectivity options. Catalyst switches with Gigabit Ethernet ports have standardized rectangular openings that accept Gigabit Interface Converters (GBICs). GBIC modules provide the media personality for the port so that various types of cables can be connected. In this way, the switch chassis is completely modular and requires no major change to accept a new media type. Instead, the appropriate GBIC module is...

Hierarchical Network Design

The campus network can be structured so that each of the three types of traffic flows or services outlined in Table 2-3 can be best supported. Cisco has devised a hierarchical approach to network design that enables network designers to logically create a network by defining and using layers of devices. The resulting network is efficient, intelligent, scalable, and easily managed. The hierarchical model breaks a campus network down into three distinct layers, as illustrated in Figure 2-6....

How to Best Use This Chapter

By taking the following steps, you can make better use of your study time Keep your notes and answers for all your work with this book in one place for easy reference. Take the Do I Know This Already quiz and write down facts and concepts (even if you never look at the information again). Use the diagram in Figure 2-1 to guide you to the next step.

How to Use This Book to Pass the Exam

One way to use this book is to start at the beginning and read it cover to cover. Although that would help you prepare, most people would not take that much time, particularly if you already knew a lot about some of the topics in the book. The rest of you might want to consider a different strategy on how to best use this book, depending on what training you have had. This book is designed to help you get the most out of the time you take to study. At the beginning of each chapter, you are...

HSRP Status

To display the status of the HSRP router, enter the following command in privileged EXEC mode. Router show standby type-number group brief The command options for this command are defined as follows type-number This optional argument indicates the target interface type and number for which output is displayed. group This optional argument indicates a specific HSRP group on the interface for which output is displayed. brief This option displays a single line of output summarizing each standby...

I

The conventions used to present command syntax in this book are the same conventoins used in the IOS Command Reference. The Command Reference describes these conventions as follows Vertical bars (I) separate alternative, mutually exclusive elements. Square brackets indicate optional elements. Braces indicate a required choice. Braces within brackets indicate a required choice within an optional element. Boldface indicates commands and keywords that are entered literally as shown. In actual...

IGMP Version

IGMP uses IP datagrams to transmit information about multicast groups. The datagram consists of a 20-byte IP header and an 8-byte IGMP message. According to the IGMPvl specification, one multicast router per LAN must periodically transmit Host Membership Query messages to determine which host groups have members on the querier's directly attached networks. IGMP query messages are addressed to the all-host group (224.0.0.1) and have an IP Time-To-Live (TTL) equal to one. This TTL ensures that...

Input Access Lists

As with output access lists, placing an input access list on an MLS-enabled interface purges the MLS cache of all existing flows for that interface. Because the default behavior for the input access list is to examine and route all incoming packets, however, all subsequent packets in the flow between Hosts A and B are routed. Most input access lists can be implemented as output access lists to achieve the same effect. Routers configured with Cisco IOS Release 11.3 or later will not...

InterVLAN Routing Configuration

This section presents a more detailed look at configuring interVLAN routing using both external and integrated Cisco route processors. Routing, in itself, is a complex and extensive topic. Only the basic routing protocol configuration is presented here, to provide simple but functional routing between VLANs. If you need further information on the various routing protocols, refer to the Interconnecting Cisco Network Devices (ICND) and Building Scalable Cisco Networks (BSCN) courses or course...

IP Extended Access List Overview

An extended access list follows many of the same principals of a standard access list. However, an extended list provides for a higher degree of control by enabling filtering based on the source address as well as the destination address, the protocol type, and the application or port number. Extended access lists have the following characteristics Top-down processing of the access list. As soon as a match is made in the access list, it stops processing and either permits or denies the packet...

IP Route Filtering

Consider the network device setup in Figure 12-7. The command syntax in Example 12-11 indicates that the routing process of Enhanced Interior Gateway Routing Protocol (EIGRP) will send the network of 140.20.0.0 255.255.0.0 in its routing updates out E0 0 (Ethernet) but will filter all other networks. If the core is connected to VLAN10, it will receive only 140.20.15.0 and only 140.20.15.0.0 will be allowed to traverse the core. Example 12-11 Configuring IP Route Filtering The options for the...

Issues with Traditional Methods

This section deals with various traditional methods that have been used, but for one reason or another are ineffective in some failure modes. These methods include default gateways, proxy ARP, RIP, and IRDP. In Figure 9-2, Router A is responsible for routing packets for Subnet A, and Router B is responsible for handling packets on Subnet B. If Router A goes down or otherwise becomes unavailable to the PC, the routing protocols used between the rest of the routers will converge at some point and...

Ive Learned Switching From Experience But I Will Not Be Taking the Bcmsn Course Now What

If you feel that you know a fair amount about switching topics already but are worried about the topics you have not worked with, some study strategies to follow are Use this book exactly as described in the opening pages of each of Chapters 2 through 13. Each chapter begins with a quiz that helps you assess the basic topics you need to study. The quiz also directs you to the appropriate sections of the chapter to increase your knowledge on specific topics rather than requiring you to read the...

Ive Taken BCMSNNow What

For starters, you've taken the best path to prepare yourself. However, retaining and recalling most of the material covered in an instructor-led course is difficult after some time has passed. To reinforce what you've learned in the course, here are some strategies to follow Use this book exactly as described in the opening pages of each of Chapters 2 through 13. Each chapter begins with a quiz that helps you assess the basic topics you need to study. The quiz also directs you to the...

Kl

LAN (local access network) segmentation model, 2530 LAN Emulation (LANE), 111 LAN Emulation Client (LEC), 214 LAN Emulation Configuration Server (LECS), 215217 LAN Emulation Server (LES), 215-216 LANE (LAN Emulation), 111 address resolution, 218 ATM, 213-214, 248-249 configuring, 220-227 membership, 216-220 components, 219-220 viewing, 224-227 VLAN connectivity, 253 lane server-bus ethernet command, 223 Layer 2 switching, 20 Layer 3 switching, 22, 48 Layer 4 switching, 22 Layer 3 routing, 21...

LAN Segmentation Model

Referred to as network segmentation, localizing the traffic and effectively reducing the number of stations on a segment is necessary to prevent collisions and broadcasts from reducing a network segment's performance. By reducing the number of stations, the probability of a collision decreases because fewer stations can be transmitting at a given time. For broadcast containment, the idea is to provide a barrier at the edge of a LAN segment so that broadcasts cannot pass or be forwarded on...

LANE Component Redundancy SSRP

Although LANE can be implemented as separate components dispersed throughout a network, each component is still a single point of failure. The ATM Forum's LANE 1.0 standard only allows a single LECS for a network, and a single LES and BUS for each ELAN. However, Cisco has implemented a redundancy protocol for LANE that allows multiple LECS, LES, and BUS components. Simple Server Redundancy Protocol (SSRP) provides communication between the primary active component and one or more standby...

LANE Components

To understand how LANE works within a larger switched network, you should first understand how emulated LANs (ELANs) differ from virtual LANs (VLANs). Recall that virtual LANs are used on Catalyst switches as a means to segment traffic into logical networks. VLANs can also be trunked between switches. Similarly, ELANs are used by ATM devices to segment traffic into logical networks. However, ELANs exist only within the ATM domain. ELANs and VLANs remain separate except where they are physically...

LANE Configuration

This section discusses the procedures for configuring the various LANE components on Cisco Catalyst switches. The order that the components are configured is important because each component is dependent upon another. On Cisco ATM devices, ELANs are configured on ATM subinterfaces. This configuration makes it possible to support many ELANs over a single ATM link. As well, the LANE components necessary for a specific ELAN must be configured on the respective subinterface for that ELAN (ATM 0.1,...

Layer 3 Core

Layer 3 switching can also be used in the core to fully scale the core block for large campus networks. This approach also overcomes the problems of slow convergence, load balancing limitations, and router peering limitations. Figure 2-11 shows a network design using a Layer 3 core. Notice that the network structure is identical to one using a Layer 2 dual core. The main difference is that the core devices operate at Layer 3. Also notice that the core switches can have direct links to each...

Layer 4 Switching

Devices involved in Layer 4 switching perform the following functions Packets are forwarded using hardware switching, based on both Layer 3 addressing and Layer 4 application information. Layer 3 protocol types (UDP or TCP, for example) in packet headers are examined. Layer 4 segment headers are examined to determine application port numbers. Switching at Layer 4 allows finer control over the movement of types of information. For example, traffic can be prioritized according to the source and...

Managing Multicast Traffic

In the world of multicasting, the concept of sending a multicast within a single broadcast domain is a somewhat trivial process. However, when we extend this into multiple segments within a campus environment over multiple switches and routers, we complicate matters significantly. The sending process specifies a destination address defined as a multicast address. The device driver in the sending server converts this address to the corresponding Ethernet address and sends the packet out on the...

Mapping IP Multicast Addresses to Ethernet

Ethernet frames have a 48-bit destination address field. To avoid invoking the Address Resolution Protocol (ARP) to map multicast IP addresses to Ethernet addresses, the IANA designated a range of Ethernet addresses for multicast. The lower 23 bits of the Class D address are mapped into a block of Ethernet addresses that have been reserved for multicast. This block includes addresses in the range 00 00 5e 00 00 00 through 00 00 5e ff ff ff. The IANA allocates half of this block for multicast...

MLS Caching

MLS caching is a process that occurs based on individual flows. In this section, we will walk through the process, step by step, in order to gain an intimate knowledge of just what occurs. The Switching Engine (SE) is involved in the process to maintain the cache for MLS flows. Packets in a flow are compared to the cache. Cache entries are based on one-way flows. In other words, a flow from Host A to Host B would be one flow and a flow in the reverse direction would be another flow. This action...

Modifying STP Timers on a CLIBased Switch

Use the following commands to modify STP timers on a CLI-based switch Switch(enable) set spantree hello interval vlan Switch(enable) set spantree fwddelay delay vlan Switch(enable) set spantree maxage agingtime vlan The Hello Timer triggers periodic hello messages to be sent to other bridges and sets the interval that a bridge expects to hear a hello from its neighboring bridges. BPDUs are sent every 2 seconds by default. The Hello Timer can be modified per VLAN with the set spantree hello...

Modifying STP Timers on IOSBased Switches

The following commands can be used on an IOS-based switch to modify STP timers Switch(config) spanning-tree vlan vlan-list hello-time seconds Switch(config) spanning-tree vlan vlan-list forward-time seconds Switch(config) spanning-tree vlan vlan-list max-age seconds The Hello Timer defaults to 2 seconds and can be set from 1 to 10 seconds per VLAN. The Forward Timer defaults to 15 seconds and can be set from 4 to 200 seconds per VLAN. The Max Age Timer defaults to 20 seconds and can be set from...