Cisco Router VRRP configuration question

[fgasimzade]

Hello everyone!

We are going to implement VRRP in our organization. Currently we have just 1 router with peer-to-peer subnet with our ISP

Say, we have an ip address of Gi0/1 1.1.1.1 and ISP has 1.1.1.2 (in real life these are public IP addresses)  and we use them to statically route our public IP addresses to the ISP

Now what we plan to do is to configure VRRP on this interface (gi0/1) and the second router's interface (gi0/1). The question is that if we are going to have our 1.1.1.1 IP as a virtual IP address, which addresses can I use for the interfaces on both routers? Can it be just any IP address from a single subnet or anything else?

Thank you!

[John Blakley]

You have to use something that is in the subnet of the virtual address that you're using. So technically, you'd need at a minimum a /29 from your ISP to use vrrp on the wan side.

VRRP will complain, as will HSRP, if you try to use a subnet different from the physical addresses:

FastEthernet0/0 - Group 10

  State is Init

  Virtual IP address is 192.168.30.2 (wrong subnet for this interface)

  Virtual MAC address is 0000.5e00.010a

  Advertisement interval is 1.000 sec

  Preemption enabled

  Priority is 100

  Master Router is unknown, priority is unknown

  Master Advertisement interval is unknown

  Master Down interval is unknown

HTH,
John

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[fgasimzade]

Thank you John,

It will complain, as I can see, but will it work?

[John Blakley · Accepted solution]

No it won't work. The group doesn't try to come up because of the error:

R2(config-if)#

*Mar  1 00:04:58.751: VRRP: vrrp_interface_state: Fa0/0 is Up

*Mar  1 00:04:58.751: VRRP: vrrp_swif_comingup: Fa0/0 now Up

*Mar  1 00:04:58.751: VRRP: Grp 10 Event - Interface UP

*Mar  1 00:04:58.751: VRRP: Grp 10 not ready to start

*Mar  1 00:04:58.755: VRRP: vrrp_interface_state: Fa0/0 is Up

*Mar  1 00:04:58.755: VRRP: vrrp_swif_comingup: Fa0/0 now Up

*Mar  1 00:04:58.759: VRRP: Grp 10 Event - Interface UP

*Mar  1 00:04:58.759: VRRP: Grp 10 not ready to start

R2(config-if)#

If I change it to the same subnet (real address is 192.168.12.2 and vIP is 192.168.12.50), the group comes up:

*Mar  1 00:06:03.647: %VRRP-6-STATECHANGE: Fa0/0 Grp 10 state Disable -> Init

*Mar  1 00:06:03.647: VRRP: vrrp_interface_state: Fa0/0 is Up

*Mar  1 00:06:03.647: VRRP: Grp 10 Event - Interface UP

HTH,
John

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[fgasimzade]

Thank you, John!