Advanced Configuration and Management Guide

Overview of Standby Router Protocol (SRP)

SRP allows alternate paths to be provided to a host. To provide path redundancy between given hosts, a virtual router with its own unique IP addresses is created. The virtual router is created by assigning these unique IP addresses to ports on existing routing switches in the network—routing switches that could provide a path between the given hosts.

NOTE: Virtual IP router addresses are in addition to the IP address assigned to each IP interface.

For example, in Figure 13.1, suppose you want to provide continual connectivity between Host 1 and Host 3 with the use of redundant paths. A virtual router is created by assigning the same virtual router IP address to all physical interfaces that will provide redundant paths for that portion of the network. Virtual router IP address

192.53.5.1is assigned to interfaces A and B, and the virtual router IP address 192.55.4.1 is assigned to interfaces C and D. Notice that in both cases, these virtual addresses are in addition to their physical IP addresses.

The virtual IP address also serves as the default router for the hosts. Hosts 1 and 2 reference the virtual IP router address 192.53.5.1 as their default router and Host 3 references the virtual router IP address, 192.55.4.1.

If Router 1 goes down, then Router 2 provides connectivity between Host 1 and Host 3.

Host 1

Host 2

 

Default Router

Default Router

 

192.53.5.1

192.53.5.1

 

192.53.5.1

192.53.5.1

192.53.5.1

192.53.5.2 (A)

192.53.5.3 (B)

Virtual

Active

Standby

Router 1

Router 2

Router

 

Preference = 200

Preference = 60

 

192.55.4.2 (C)

192.55.4.3 (D)

 

192.55.4.1

192.55.4.1

192.55.4.1

Default Router 192.55.4.1

Host 3

Router 1:

Router 2:

IP Address for Interface A: 192.53.5.2

IP Address for Interface B: 192.53.5.3

Virtual Router IP address for Interface A: 192.53.5.1

Virtual Router IP address for Interface B: 192.53.5.1

IP Address for Interface C: 192.55.4.2

IP Address for Interface D: 192.55.4.3

Virtual Router IP address for Interface C: 192.55.4.1

Virtual Router IP address for Interface D: 192.55.4.1

Figure 13.1 SRP operating in an HP 9304M network

 

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