ARP issues using VRRP on ARNs

[jacipaci]

Hi there

Has anyone come across this before? I have set up two Nortel ARNs running VRRP. The routers are switching over without issue in testing, however I have a problem with the LAN. The issue happens when the Backup becomes the Master. I'm unable to ping the virtual IP address without clearing the ARP entry on the PC as it is picking up the actual MAC address for both routers. However, it works fine in reverse when the Primary router again becomes the Master.. When I check the ARP table on the PC, there is a virtual MAC address associated with the IP address as there should be.
Any ideas?! Thanks, JC

 

[Jynxx]

I may be totally misunderstanding what you are saying...but how does the PC have an ARP table? The only devices to my knowledge that would contain an ARP table would be layer 3 devices...

Unless you mean that you have to clear the ARP entry FOR the PC's IP address on the router? If so, then that may very well be a bridging/forwarding table issue on the switch.

Do you mean that you flush the dns? If so, then I would think it to be a DNS issue vs an arp issue.

If you check the switch that the routers plug in to, what does it's bridging table look like?

 

[jacipaci]

Many thanks for the suggestions, its much appreciated but I sorted the issue. The reason the PC was losing connectivity to the ARNs was due to fact that the virtual address was matching the physical ethernet address of the Master router.

When using VRRP, a virtual MAC address is generated which is associated with the virtual IP address. As I had set it incorrectly, this meant that the PC was picking up both the actual physical MAC addresses of the two ARNs and the virtual MAC address generated by VRRP and then associating it with each of the IP addresses at various times depending on whether they were Master or backup at that stage.

What I ended up doing was to set the Virtual IP address on the ARN to match the default gateway of my PC's on both ARNs. This meant that no matter what router was physically up and running as Master, the default gateway always had its own MAC address. And therefore no confusion for the PCs on the LAN.

FYI, a PC does have ARP entries...if you haven't seen this before try an arp -a entry in DOS on your own PC.