© 1999, cisco systems, inc. 6-1 intervlan routing chapter 6

© 1999, Cisco Systems, Inc. 6-1

InterVLAN Routing

Chapter 6

© 1999, Cisco Systems, Inc. www.cisco.com BCMSN—6-2

ObjectivesObjectives

Upon completion of this chapter, you will be able to perform the following tasks:• Identify the network devices required to effect

interVLAN routing

• Configure a default gateway to ensure networkreachability

• Configure a route processor to facilitateinterVLAN routing


InterVLAN RoutingInterVLAN Routing

In this chapter, we discuss the following topics:

• InterVLAN routing issues

• Distribution layer topology

• Configuring interVLAN routing



In this section we discuss the following topics:

• InterVLAN Routing Issues

–Isolated Collision Domains

–Finding the Route

–Supporting Multiple VLAN traffic

• Distribution Layer Topology

• Configuring InterVLAN Routing


Problem: Isolated Broadcast Domains

Problem: Isolated Broadcast Domains

VLAN10 VLAN20

172.16.20.4

VLAN30

• Because of their nature, VLANs inhibit communication between VLANs


Solution: Routing Between VLANs

Solution: Routing Between VLANs

VLAN10 VLAN20

172.16.20.4

VLAN30

• Communications between VLANs require a routing processor


Problem: Finding the RouteProblem: Finding the Route

VLAN10

Network 172.16.10.0

172.16.10.3

VLAN20

Network 172.16.20.0

172.16.20.4

I need to send this packet to 172.16.20.4. That

address is not on my local segment.

I need to send this packet to 172.16.20.4. That

address is not on my local segment.

• InterVLAN communications introduce the problem of where end-user stations send nonlocal packets


Solution: Defining a Default Gateway

Solution: Defining a Default Gateway

VLAN10

Network172.16.10.0

172.16.10.3

VLAN20

Network 172.16.20.0

172.16.20.4

I know where network

172.16.20.0 is!

I know where network

172.16.20.0 is!

I will send the packet to

my default router.

I will send the packet to

my default router.

• End-user stations send nonlocal packets to a default router


VLAN20VLAN10

Problem: Supporting Multiple VLAN Traffic

Problem: Supporting Multiple VLAN Traffic

VLAN30

I have three distinct streams of traffic destined for

the same place!

I have three distinct streams of traffic destined for

the same place!

? ?

File Server A172.16.3.127

I need informationfrom File Server A.I need informationfrom File Server A.

I need informationfrom File Server A.I need informationfrom File Server A. I need information

from File Server A.I need informationfrom File Server A.

• Multiple VLANs interfacing with a single route processor require multiple connections or VLAN trunking

? ?


VLAN60

VLAN10 VLAN30VLAN20

Solution: Multiple LinksSolution: Multiple Links

• The router can support a separate interface for each VLAN


Solution: Inter-Switch LinkSolution: Inter-Switch Link

Eth 3/1.1 3/1.2 3/1.3

• The router can support a single ISL link for multiple VLANs

VLAN10 VLAN30VLAN20

Eth 3/0.1 3/0.2 3/0.3

VLAN60




• InterVLAN Routing Fundamentals

• Distribution Switch Topology

–External Route Processors

–Internal Route Processors



Distribution Layer Route Processors

Distribution Layer Route Processors

Distribution Layer

• The distribution-layer device is a combination of a high-end switch and a route processor


External Route ProcessorExternal Route Processor

Switch C

Switch A Switch B

VLAN41Network 172.16.41.3



• An external Cisco high-end router and a Catalyst 5000 switch with an NFFC or NFFCII

• Connected by multiple Ethernet connections or an ISL link


Internal Route Processors Internal Route Processors

• Multilayer switches integrate Layer 2 and Layer 3 functionality in a single box





Internal Route Processors (cont.) Internal Route Processors (cont.)

• RSM can reside in slots 2 through 12 of a Catalyst 5000 switch

RSM

• RSFC is a daughter card on the Supervisor Engine IIG and IIIG

RSFC




• InterVLAN Routing Fundamentals

• Distribution Layer Topology


–Locating and accessing the routeprocessor

–Configuring an interface

–Defining a default gateway

–Testing the link


Locating the Route ProcessorLocating the Route Processor

Switch (enable) show module

• Specifying a particular module number displays information on that module

• Not specifying a module number displays information on all modules installed in the system

Mod Module-Name Ports Module-Type Model Serial-Num Status--- ------------- ----- --------------------- --------- --------- -------1 0 Supervisor III WS-X5530 010821493 ok2 24 10/100BaseTX Ethernet WS-X5225R 012145458 ok3 1 Route Switch WS-X5302 006825295 ok


Accessing the Route Processor

Accessing the Route Processor

Switch (enable) session 3

• Eliminates the need to connect a terminal directly to the RSM console port


Identifying the Route ProcessorIdentifying the Route Processor

• The hostname uniquely identifies each route processor within the network

Router(config)#hostname RSM143Router(config)exitRSM143#


Enabling an IP Routing Protocol Enabling an IP Routing Protocol

• Routing protocols determine optimal paths through the network and transport information across these paths

RSM141(config)#ip routingRSM141(config)#router igrp 1RSM141(config-router)#network 172.16.0.0

172.16.10.0 172.16.30.0

172.16.20.0 Network172.16.0.0


Configuring an VLAN Interface on an Internal Route Processor

Configuring an VLAN Interface on an Internal Route Processor

RTR144(config)#interface vlan41RTR144(config-if)#ip address 172.16.10.3 255.255.255.0RTR144(config-if)#exitRTR144(config)#interface vlan42RTR144(config-if)#ip address 172.16.20.3 255.255.255.0RTR144(config-if)#exit

• The internal route processor automatically encapsulates packets using ISL• Initial configuration requires a no shutdown command


RSM144(config)#interface fastethernet 0/1.1RSM144(config-if)#encapsulation isl 10RSM144(config-if)#ip address 172.16.10.3 255.255.255.0RSM144(config-if)#exitRSM144(config)#interface fastethernet 0/1.2RSM144(config-if)#encapsulation isl 20RSM144(config-if)#ip address 172.16.20.3 255.255.255.0RSM144(config-if)#exit

Configuring an VLAN Interface on an External Route Processor

Configuring an VLAN Interface on an External Route Processor

• Subinterfaces allow for routing multiple data streams through a single physical interface

• Initial configuration requires a no shutdown command

Slot

Interface FA 0/1Subinterface 0/1.1

Interface FA 0/1Subinterface 0/1.2

Subinterface NumberPort

VLAN10

VLAN20

Encapsulation Type and VLAN Number


Defining a Default GatewayDefining a Default Gateway

VLAN40

VLAN30

ASW31#config tEnter configuration commands, one per line. End with CNTL/ZASW31(config)#ip default-gateway 172.16.1.163

ASW41#config tEnter configuration commands, one per line. End with CNTL/ZASW41(config)#ip default-gateway 172.16.1.163

172.16.1.163

Default Gateway172.16.1.163

Default Gateway172.16.1.163

• Defining a default gateway facilitates interVLAN communications


Testing the LinkTesting the Link

PC41#ping 172.16.10.3Sending 5, 100-byte ICMP Echos to 172.16.10.3, time out is 2 seconds:!!!!!Success rate is 100 percent (5/5), round-trip min/avg/max 0/0/0/ ms

• The ping command tests connectivity to remote hosts


Laboratory Exercise: Visual Objective

Laboratory Exercise: Visual Objective

Switch Block X

VLAN x1

VLAN x3

VLAN x2

VLAN x4


Summary Summary

• InterVlan routing is a requirement to enable communication between devices in separate VLANs.

• Most devices are configured with the IP address of a default router to which all non-local network packets are sent.

• The Inter-Switch Link (ISL) protocol is used to facilitate multiple VLAN traffic over a single link.

• The distribution layer routing processor can be an internal or external router/switch topology.


Review Review

• List at least two problems that can impede communications between VLANs, and identify a solution for each problem.

• Identify at least two Cisco platform solutions for an internal route processor topology at the distribution layer.

• Compare and contrast the steps used to configure an interface on an RSM and an ISL link on an external router.

© 1999, cisco systems, inc. 6-1 intervlan routing chapter 6

Documents

intervlan routing slide

cisco systems

intervlan routing chapter

routing processor slide

vlans slide

vlan slide

default router slide

intervlan communications