Could it be an access list? Are you allowing UDP packets to pass through on port 53? This should be enough if there is no ACL issue:     ip domain name server.serve ip name-server 208.67.222.222 ip name-server 208.67.220.220 ip dns view default    dns forwarder 208.67.222.222    dns forwarder 208.67.220.220 ip dns server queue limit forwarder 1500 ip dns server     Then maybe put this access list on your WAN interface in: ip access-list extended DENY-DNS-FROM-WAN  permit udp host 208.67.220.220 any eq domain  permit udp host 208.67.222.222 any eq domain  deny   udp any any eq domain  permit ip any any   ... View more

I have the a similar problem. It is not exactly the same, but the Cisco 1801 router also stops serving DNS responses to clients. Clearing the hosts table seems to be the only solution. I have tried to resolve the issue. to no avail, by limiting the forwarding with the command: #ip dns server queue limit forwarder 'VARIOUS INTEGERS' I believe that my problem stems from running too much on the router. The memory  gets full and seems to cause this issue for me. I have turned off layer 7 filtering (using nbar), and I am watching now for improvement.  ... View more

Hello, I think you should implement Service Level Agreement tracking combined with route maps. It will track the state of you WAN interfaces, either up or down, and load balance through the up WAN interfaces. It would look something like this: ip sla 1  icmp-echo W.A.N.x source-interface Dialer1 timeout 1000 threshold 40 frequency 3 ip sla schedule 1 life forever start-time now ip sla 2  icmp-echo W.A.N.y source-interface Dialer2 timeout 1000 threshold 40 frequency 3 ip sla schedule 2 life forever start-time now ! ! track timer interface 5 !         track 100 interface Dialer1 ip routing delay down 15 up 10 !         track 200 interface Dialer2 ip routing delay down 15 up 10 ! ! no ip classless ip route 0.0.0.0 0.0.0.0 Dialer1 track 100 ip route 0.0.0.0 0.0.0.0 Dialer2 track 200 ! ! route-map dialer2 permit 10 match ip address 100 match interface Dialer2 !         route-map dialer1 permit 10 match ip address 100 match interface Dialer1 Ther'es not not much more to it than that. Just use the ol' NAT inside/outside configuration for all interfaces. Of course you can throw some OER/PfR in for added complexity. ... View more

jcarvaja, your disagreement is in error. These are layer three protocols. I linked to the documentation to provide the definative answer. The OSI model classification of protocols is not like a layer cake; in that you can't say because this protocol relies on a layer 4 TCP or UDP, that it must therefore be higher on the OSI model than layer 4. Rather the protocols are classified by the services they provide. RIP and BGP provide layer 3 services. ... View more