6500 MSFC and HSRP subnet masks

[griffp]

I am currently configuring the routing interfaces on 6500 MSFCs.

When a standby IP is added to an interface how does the router know how you are subnetting the IP ranges?

For instance if I enter 10.10.10.1 as a standby IP how does it know whether I am using an 8, 16, 24 or even a 27 bit subnet mask?

It does not enforce entering a subnet mask when you add a standby IP.

[glen.grant]

I'm sure it looks at what is configured as the normal address on the interface and applies the same mask .

[griffp]

Thanks, I was afraid of that. I have 12 VLANs and a few of them have at least four secondary IPs.

I'll have to dig out quite a few IP addresses for this job.

[Kevin Dorrell]

For each VLAN, you will need three IP addresses for your routers (one for each plus the standby address), plus three for each secondary address range (again, one for each router, and one for the standby address). You enter the standby address for the secondary range like standby group-number ip ip-address secondary. As far as I can see from the doc, you use the same standby group number for the secondary addresses as you do for the primary addresses.

Kevin Dorrell

Luxembourg

[griffp]

Kevin,

Thanks for clearing that up. That confirms the way forward.