HSRP Operations

[karl.jones]

Hi

I am looking to have a 3550switch with emi and a 3660 on the same LAN and perform HSRP between them with the 3550 being the Active router. The 3660 has frame spokes hanging off it. Even tho I am performing HSRP, will I still be able to route through the standby interfaces on the 3660 to get to the spoke routers.

Will it work?

Any advice would be greatly appreciated, plus any web example integrating router with switch would be good.

Best regards

[gvpelt]

Hi,

This is a tricky configuration.

All hosts will send the traffic to the 3550 switch/router, even if the traffic is for the spoke routers after the 3660 router.

Normally the 3550 switch/router will send an ICMP redirect to the host that this ip destination is reachable via the 3660 router, but with HSRP is not recommended and default disabled because of the redundancy.

The 3550 switch/router will not send the traffic back out the same interface to the 3660 router.

But you can do this!

What you can do is make an extra “transit” vlan and enable a routing protocol on this transit vlan.

So the traffic comes in vlan x on the 3550 switch/router and this traffic is send out to the 3660 router on the transit vlan.

For more info about HSRP and ICMP redirect see:

http://www.cisco.com/univercd/cc/td/doc/product/software/ios121/121newft/121t/121t3/dt_hsrpi.htm

[karl.jones]

I think I know what you mean with the transit vlan but have you got a web page for this.

Why wont the 3550 send the traffic back out the same int to the 3660.?? If this is not poss, this transit domain, would it be a vlan with no clients on that has a preffered metric routing between the router and the switch, so data isnt sent back out on the same int on the 3550 but across this transit vlan.

Is that how it works?

Thanks for reply

[gvpelt]

Sorry,

I was wrong, you can use HSRP without a transit vlan. The packet will route out the same interface.

Yes a transit vlan has no clients.

So a basic HSRP configuration is fine for your setup.

Good luke

GF