© 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
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InterVLAN RoutingInterVLAN Routing
In this chapter, we discuss the following topics:
• InterVLAN routing issues
• Distribution layer topology
• Configuring interVLAN routing
© 1999, Cisco Systems, Inc. www.cisco.com BCMSN—6-4
InterVLAN RoutingInterVLAN 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
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Problem: Isolated Broadcast Domains
Problem: Isolated Broadcast Domains
VLAN10 VLAN20
172.16.20.4
VLAN30
• Because of their nature, VLANs inhibit communication between VLANs
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Solution: Routing Between VLANs
Solution: Routing Between VLANs
VLAN10 VLAN20
172.16.20.4
VLAN30
• Communications between VLANs require a routing processor
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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
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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
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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
? ?
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VLAN60
VLAN10 VLAN30VLAN20
Solution: Multiple LinksSolution: Multiple Links
• The router can support a separate interface for each VLAN
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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
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InterVLAN RoutingInterVLAN Routing
In this section we discuss the following topics:
• InterVLAN Routing Fundamentals
• Distribution Switch Topology
–External Route Processors
–Internal Route Processors
• Configuring InterVLAN Routing
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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
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External Route ProcessorExternal Route Processor
Switch C
Switch A Switch B
VLAN41Network 172.16.41.3
VLAN41Network 172.16.41.4
VLAN42Network 172.16.42.5
• 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
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Internal Route Processors Internal Route Processors
• Multilayer switches integrate Layer 2 and Layer 3 functionality in a single box
VLAN41Network 172.16.41.4
VLAN42Network 172.16.42.5
VLAN41Network 172.16.41.3
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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
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InterVLAN RoutingInterVLAN Routing
In this section we discuss the following topics:
• InterVLAN Routing Fundamentals
• Distribution Layer Topology
• Configuring InterVLAN Routing
–Locating and accessing the routeprocessor
–Configuring an interface
–Defining a default gateway
–Testing the link
© 1999, Cisco Systems, Inc. www.cisco.com BCMSN—6-18
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
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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
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Identifying the Route ProcessorIdentifying the Route Processor
• The hostname uniquely identifies each route processor within the network
Router(config)#hostname RSM143Router(config)exitRSM143#
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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
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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
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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
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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
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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
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Laboratory Exercise: Visual Objective
Laboratory Exercise: Visual Objective
Switch Block X
VLAN x1
VLAN x3
VLAN x2
VLAN x4
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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.
© 1999, Cisco Systems, Inc. www.cisco.com BCMSN—6-29
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.