HSRP and non-Cisco Switches

[fvalpondi]

Hi everyone,

I just wanted to ask you about HSRP interoperating with non-Cisco switches.

I got two Cisco 2800s with four different interfaces (3x FastEth, 1x ISDN).

HSRP will be configured for three of them (the fourth is an ISDN connection, and as far as I know, HSRP does not work with ISDN interfaces).

Well, the both routers will be connected in each network to a non-cisco switch (i proposed Catalyst, but the Boss said it had to be with unmanaged D-Link).......

My question is:

- HSRP uses a well-known MAC address for identify the interfaces.

- The switch will register this MAC address in the MAC-Table for each router. It means that he active link will have the well-known HSRP-MAC address.

- What will happen if the router fails? After all, the HSRP-MAC address will still be in the Forwarding Table of the switch, right?

- Will it not be a problem for the switch this issue?

- Which solution do I have? The switch is non-managed......

Thanks a lot! ;-)

Best regards,

Fabio

[Giuseppe Larosa · Accepted solution]

Hello Fabio,

what Simon is saying is that when an HSRP switchover happens the new active device will send out a Gratuitous ARP.

The frame has a destination of broadcast and a MAC source = HSRP VIP MAC addres.

in this way switches CAM tables are updated.

This should work even with unmanaged switches like the ones you have to use.

Actually without that gratuitous ARP HSRP would be of no use with any type of LAN switches it is a needed step.

PCs ARP tables are not affected by this message because it restates known information

Hope to help

Giuseppe

[simontibbitts]

Hi Fabio.

Sorry I meant to say you will NOT have a problem!

Sorry for the typo!

Simon