Multiple ADSL - VRF DNS Issue

[nathanhagd]

Hi All,

I have a bit of a problem and was hoping someone might be able to help me out.

Basically I am trying to do a bit of a clean up at work and replacing  two dlink (home style) ADSL modems with a single Cisco 2901 router with  2 ADSL HWICs. On top of this I want to isolate the 2 connections from each other,  that is I don't want to use them as fail-over or anything just as 2  seperate connections. To do this I am using VRF tunnels.

So far I have been successful in the global config of the switch and  everything works. And when I put the lan, atm and dialer interface into  my VRF it connects up all fine.My issue that I am having is that DNS (which is being pulled from the  ISP via ppp ipcp dns) seems to just populate the global dns view, not  the view I created for the VRF. This results in DNS queries not being  able to be resolved but all other traffic is fine (i.e. I can ping and  access anything on the net, I just can't resolve names).

So my question is... If I have 2 ADSL connections, on two VRF  tunnels, how can I seperate their DNS information for each  connection/VRF tunnel? especially if that information is different as  they overwrite the global DNS config each time they connect.... I could  (and have successfully tested) statically assigning DNS servers to each  DNS view but I would rather rely on each ISP sending their DNS servers  as opposed to me hard coding them.

Hopefully that makes some sense and someone out there may have an idea, all help is appreciated.

[leighharrison]

Hi there Nathan,

From what I understand, is it that you've set the DNS on the router itself and the issue you've got is that when you ping an dns name from one vrf it's fine and from another it doesn't work?

If that's the case, then I think you may be a little limited as the DNS entry for the router is for the router itself to use.  The only way I can think of getting around it would be to plug the router into a switch, send a vlan down with each vrf and use a pc connected into either vlan and define DNS servers from there - 8.8.8.8 is always a good one.

Failing that, you could use the switch in the vrf without DNS and use that to do the pinging.

HTH

LH

[nathanhagd]

Hi Leigh,

Thanks for the reply.

What is happening is that any DNS request from the VRF is trying to resolve that DNS request through the global config, not the VRF. This is odd, because the VRF can actually see the name servers (it lists them as it tries to ping) but does not seem to send the actual DNS request through the VRF so the resolution never gets done.

Also, the DNS for the router is being populated by the carrier thought the PPP IPCP DNS Request Accept command on the dialer.