Broadband connectivity drops.

[grambo1980]

sh ver | i IOS|(revision)

Cisco IOS Software, 2801 Software (C2801-ADVIPSERVICESK9-M), Version 12.4(3g), RELEASE SOFTWARE (fc2)

Cisco 2801 (revision 6.0) with 235520K/26624K bytes of memory.

Hello,

We've been seeing our WAN connection drop every 20 minutes or so. (Give or take 5-10 min)

This router is connected to a Time warner cable modem (Zyxel). We are using GRE over IPsec to tunnel the traffic.

Basically what we are seeing is we see the connectivity drop, and will not restore until the ARP table is cleared.

They've replaced the modem and done numerous config checks on it. and nothing comes back of intrest.

So one thing I did see that makes me think its an issue on TW side of things is when i do a debug arp I see alllll of TW's ARP traffic being forwarded from their upstream router. I don't see this traffic on any of our other routers with similar configurations. But this along with the fact that a "clear arp" litterly fixes the issue in seconds makes me think its the problem.

I honestly have never seen anything like this and would be intrested in any opinions.

I attached a quick log of a debug arp. I also X'd and Y'd out our real ip/mac.

Thanks.

[ed.mcandrew]

Well I'm confident that the drops have something to do with ARP requests from the modem... Every time (I mean EVERY TIME)I experience a drop, I see the following in the syslog... What's funny is that every now and again, there is an occassional "wrong cable", with no drop, but for each drop I see, there is an associated "wrong cable" message. But these are the ONLY messages like this that I'm seeing whatsoever. Not a kazillion like you had.

2008-12-18 12:15:59 Local7.Debug 10.0.0.254 415576: 1007097: Dec 18 12:15:55.455 PCTime: IP ARP req filtered src 192.168.1.1 0019.cb51.74a8, dst xx.xx.xx.185 0000.0000.0000 wrong cable, interface FastEthernet0/0

2008-12-18 12:15:59 Local7.Debug 10.0.0.254 415577: 1007098: Dec 18 12:15:57.475 PCTime: IP ARP req filtered src 192.168.1.1 0019.cb51.74a8, dst xx.xx.xx.190 0000.0000.0000 wrong cable, interface FastEthernet0/0

[Douglas Fernando Fischer]

Hello,

I can confirm that EVERY TIME that will happen a drop, I see a  ---- *Oct 28 14:11:21.992 NYC: IP ARP req filtered src 192.168.0.1 c417.feff.38e6, dst ??.??.??.?? 0000.0000.0000 wrong cable, interface FastEthernet0/0 ---- as said by ed.mcandrew.

And I can confirm also that the problem happens around 15 minutes, or 14 minutes and a few seconds as said by ed to.

I will try to force 10Mb to see if it goes to 2 hours...

And they (T.W.C.) also tried to convince us that "Everything is working OK with the modem", and all those automatic answers by-the-book.

What I did as a workaround to this was a kron to every minute "clear arp-cache".

It works, but causes some loss of packets between the start of drops and the next execution of "clear arp-cache".

I will fill myself with patience and try one more time, now with the logs and the experience of you on hand, a call to their support.

Lets see if we can solve this problem.

If I could solve this problem without depending of Time Warner Support, it would make me happy.

I was thinking in some thing around send and receiving gratuitous arp, broadcasts and etc...

Any sugestions?

[Douglas Fernando Fischer]

Just to inform

The modem that is been used in this connection is a ubee ddw3611com.Some how, my colleague in NYC reached a good technician at Time Warner. Believing or not, they exists.

This guy upgraded the firmware of the modem, and everything was OK.

I removed the "clear arp" every minute kron, and all is good.