Saturated serial interface - help!!

Unanswered Question
Mar 2nd, 2009

I've got a serial interface on a 2811 router that has been showing an rx load of 252/255 for about 60 hours.

I've got netflow enabled on it and when I put an ACL on the serial interface to block the offending IP address it does not seem to be working. I've got the log parameter on there and its not showing in the log and the rx load is not decreasing.

Netflow shows it as protocol 27 and the source and destination addresses are not any of the networks configured on this router.

What is going on here? Thanks for any help on this.

I realize that I posted in the network managemetn forum but I really need some direction on this. Thank you again in advance!

I have this problem too.
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pciaccio Mon, 03/02/2009 - 09:15

If you can try shutting the interface down to stop the flood and bring it back up to see if it starts back up again. Can you also submnit the ACL that you have applied to your serial interface on the input. Can you also provide information about the source and destination of your issue.....

justin.gerharte... Mon, 03/02/2009 - 09:23

access-list 111 deny 27 host host log

access-list 111 deny ip host any log

access-list 111 deny ip host any log

access-list 111 permit ip any any

The ACL 111 is from yesterdays attempt. Netflow today is showing source of and a destination of with a source port of 17.

justin.gerharte... Mon, 03/02/2009 - 09:46

The destination has changed to This traffic is also showing up on Fa 0/0 of the router but is not hitting the firewall according to tcpdump. I wouldn't expect to to based on the foreign IP addresses and routing.

Paolo Bevilacqua Mon, 03/02/2009 - 10:00

Hi, seek help from the upstream provider, first question is why you're receiving packets that are not your network. Either you're under a flood attack but not sure how,or something seriously wrong with your ISP.


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