HSRP like solution

[eugene2004]

There is a LAN core as two of Catalyst 65xx.

7206 is way to connect this core. 7206 uses two Gigabit interfaces. One attached to first 65xx the second is to second 65xx.

one moment we need only one 7206's interface and we'd like to have the other one as a standby. Because we need only one IP address (we can not have one IP on both interfaces of 7206). If one of 65xx goes down or STP makes some changes etc then one link to 7206 is disabled.

The question: how to organize HSRP like model inside one router between two interfaces?

[a.awan]

HSRP cannot be used between two interfaces of the same router to provide redundancy; it is meant to be more of an inter-gateway redundancy protocol. I can think of two solutions that can meet your requirements:

Solution 1:

Use the backup interface command on the standby interface. This will allow you to configure both interfaces with the same IP Address, however, the standby interface will not be in an operational state unless the primary interface goes down.

Solution 2:

Configure IRB and define a logical BVI interface with the single IP address you have. Make both Gigabit Ethernet interfaces part of the same bridge-group that corresponds to the BVI interface. There are two things to note here; one is that STP will be involved and link failover times might not be acceptable (30 seconds at least without any timer manipulation). The second thing to lookout is the affect of IRB on the performance of the router. I am not sure if IRB has been added to the CEF switching path or not.

[Kevin Dorrell]

I don't think there is a way to do HSRP between two interfaces of the same router.

However, there is an architecture I could suggest - I have never tried it myself, and it might be a bit messy to configure, but you could try it. no idea what the performance would be like, nor how scaleable it is, but here goes:

On each Gbit interface, create subinterfaces to represent each VLAN in the normal way, but don't give them IP addresses. Then pair the subinterfaces for each VLAN into a bridge, and enable IRB on the router. Set the IP address on the bridge interface. In theory, Spanning tree should take care of the redundant paths on each VLAN.

Has anyone ever tried this topology, and does it work? What are the scalability limitations?

Kevin Dorrell

Luxembourg