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 Post subject: Configuring VRRP in VRFs
PostPosted: Mon Jun 30, 2014 4:16 pm 
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Joined: Sun Jun 01, 2014 8:26 am
Posts: 4
Hi all. I am trying to configure VRRP in subinterfaces which are using VRF forwarding. Both routers have the same VRF IP addressing and is connected through trunk port to the "EtherSwitch Router". I keep getting duplicate address notification and is unable to get VRRP working correctly.

Can anyone shed some light on this?




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 Post subject: Re: Configuring VRRP in VRFs
PostPosted: Sun Jul 13, 2014 2:20 pm 
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Joined: Sun Jun 01, 2014 8:26 am
Posts: 4
Bump. Any advice is appreciated.


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 Post subject: Re: Configuring VRRP in VRFs
PostPosted: Sat Aug 02, 2014 7:07 pm 
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Joined: Sat Aug 02, 2014 6:04 pm
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thedudeabides wrote:
Hi all. I am trying to configure VRRP in subinterfaces which are using VRF forwarding. Both routers have the same VRF IP addressing and is connected through trunk port to the "EtherSwitch Router". I keep getting duplicate address notification and is unable to get VRRP working correctly.

Can anyone shed some light on this?


so both routers are using the same IP address on their subint? This will cause the conflict (they need to be different IP but same subnet). For Example: I setup a lab w/ a 3825 w/ trunk links to R1/R2 using VRF YES (10.10.10.0/29):

Interface configs:
Code:
R2:
interface FastEthernet0/0.109
encapsulation dot1Q 109
ip vrf forwarding YES
ip address 10.10.10.3 255.255.255.248
vrrp 1 ip 10.10.10.1

R1:
interface GigabitEthernet1/0.109
encapsulation dot1Q 109
ip vrf forwarding YES
ip address 10.10.10.2 255.255.255.248
vrrp 1 ip 10.10.10.1
vrrp 1 priority 120


When I configured R2 as 10.10.10.3, w/ .2 as R1 and .1 as the VIP:

Code:
R2#show vrrp brief
Interface          Grp Pri Time  Own Pre State   Master addr     Group addr
Fa0/0.109          1   100 3609       Y  Backup  10.10.10.2      10.10.10.1


However, when changing it, because they are multicasting from the same source address, it will cause a conflict, and you can see in the attachments where there are 2 separate messages from 10.10.10.2 by looking at the priority value being advertised in the message. Both Routers will get the message literally say "wut? 10.10.10.2 is me, must be duplicate! And as a result, you will see this in the debug on both sides as a result:

Code:
R2#
*Mar  1 01:00:31.703: VRRP: Grp 1 sending Advertisement checksum 66F1
*Mar  1 01:00:31.747: VRRP: Duplicate source IP 10.10.10.2 on interface Fa0/0.109
*Mar  1 01:00:32.567: VRRP: Duplicate source IP 10.10.10.2 on interface Fa0/0.109


Solution: Change the IP address on one of the router's subinterface to another address in the subnet.

Hope this helps :)




Attachments:
File comment: R2 with the 100
R2.JPG
R2.JPG [ 174.29 KiB | Viewed 2214 times ]
File comment: R1 with the 120
R1.JPG
R1.JPG [ 165.01 KiB | Viewed 2214 times ]
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