Chapter 10: Virtual Routers; Virtual Routers Overview - Extreme Networks ExtremeWare XOS Guide Manual

10 Virtual Routers
This chapter describes the following topics:
Virtual Routers Overview on page 241
●
Using Virtual Routers-BlackDiamond 10K Switch Only on page 244
●
Creating Virtual Routers on page 244
■
Adding Ports to a Single Virtual Router on page 244
■
Adding Ports to Multiple Virtual Routers on page 245
■
Adding Routing Protocols to a Virtual Router on page 245
■
Virtual Router Configuration Example on page 246
●

Virtual Routers Overview

ExtremeWare XOS supports virtual routers. This capability allows a single physical switch to be split
into multiple virtual routers. This feature separates the traffic forwarded by a virtual router from the
traffic on a different virtual router.
Each virtual router maintains a separate logical forwarding table, which allows the virtual routers to
have overlapping IP addressing. Because each virtual router maintains its own separate routing
information, packets arriving on one virtual router will never be switched to another.
However, virtual routers should not be connected together through a Layer 2 domain. Since there is a
single MAC address per switch in ExtremeWare XOS, this same MAC address is used for all virtual
routers. If two virtual routers on same switch are connected through a Layer 2 domain, the intermediate
Layer 2 switches will learn same MAC address of the switch on different ports, and may send traffic
into the wrong virtual router.
Ports on the switch can either be used exclusively by one virtual router, or can be shared among two or
more virtual routers. One reason to configure a port for the exclusive use of a single virtual router is to
be sure that only packets from that virtual router egress from that port. One reason to configure a port
to be shared by multiple virtual routers is to pass traffic from multiple virtual routers across a shared
link.
With multiple virtual routers contained on a single physical switch, some commands in ExtremeWare
XOS now require you to specify to which virtual router the command applies. For example, when you
use the ping command, you must specify from which virtual router the ping packets are generated.
Many commands that deal with switch management use the management virtual router by default. See
the ExtremeWare XOS Command Reference Guide for information on the defaults for individual
commands.
NOTE
The term virtual router is also used with the Virtual Router Redundancy Protocol (VRRP). VRRP uses the term to
refer to a single virtual router that spans more than one physical router, which allows multiple switches to provide
redundant routing services to users. For more information about VRRP, see
ExtremeWare XOS 11.3 Concepts Guide
Chapter 21.
241