I am using a Cisco 1801. I have a /30 network with one static public IP on my end and the other useable IP being the gateway on the ISP's side.
The connection works fine for a few hours, after which it just drops comms and I get no data flow. I'll power cycle the Cisco 1801 and still no data flow, but the CD light is on solid.
The odd thing is that to establish data flow again, I have to remove the Cisco 1801 and plug in a netgear router. I then plug the Cisco 1801 back in and everything works fine for a few more hours. I'm continually having to do this to get the Cisco 1801 to work.
The ISP says it's a layer 2 problem because when my connection goes down they can't see any MAC address coming from my end. Even after power cycling the Cisco 1801, they still can not see any MAC address on my end. When I plug the netgear router in, they then can see a MAC address on my end.
Is it my Cisco 1801 that's the problem or something on the ISP's side?
Is it possible that the few hours that it works is 4 hours? If it does run for 4 hours and then fail I would guess that it might be a problem in the ARP cache.
If you could give us some more information, what kind of interface, configuration of the router, pehaps show interface, and maybe show ARP, then we might be better able to see what is causing this problem.
You could try using a locally administered MAC address (replace the 1801's MAC with the MAC of the Netgear).
In the cable broadband environment, some providers enforce the use of a single MAC at the destination.
If you originally registered the Netgear as your router, something at the ISP may be trying to keep it as the only valid device.
It's pretty thin, as suggestions go, but if it comes down to the "beat your head against the wall" stage of troubleshooting, give it a shot.
It could also be a flakey 1801 (or interface). Substituting the Netgear gives the 1801 time to cool off so it's ready for another couple hours (then it heats up, flakes out, gets a break , cools off ......).
Make sure there's plenty of "breathing room" around the 1801.
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