DoS attacks and CoPP

Unanswered Question
Mar 5th, 2007


i have a few questions regarding DoS attacks and CoPP.

1. i have gone through the cisco control plane policing guide and there seem to be no hard and fast rules for deploying it. is there a one-conf-fits-all kinda solution to this? which ensures that the resources on any router are always available for legitimate traffic passing through the router as well as telnet/ssh traffic. for example if i have a 3600 series router handling 15Mb/s of traffic (and its get stuck in case of a DoS attack) and i want to make sure that the telnet session is always responsive and the router never gets stuck and there are enough resources available on it to ensure that normal traffic is always there a CoPP policy which can ensure that?

2.during troubleshooting high cpu utilization, i've observed that the "show processes cpu" command shows that the 5sec utilization is 55% but the list of processes doesnt show any single process over 0.40%. how to interpret the output of this command to find out the process taking most of the CPU time? heres an example:

router#show proc cpu

CPU utilization for five seconds: 36%/30%; one minute: 34%; five minutes: 37%

router#show proc cpu | exc 0.0

5Sec 1Min 5Min TTY Process

0.31% 0.13% 0.12% 0 Net Background

0.71% 0.78% 1.47% 0 IP Input

1.19% 0.66% 0.52% 0 IP SNMP

0.55% 0.20% 0.16% 0 PDU DISPATCHER

2.07% 1.39% 1.17% 0 SNMP ENGINE

0.47% 0.14% 0.22% 0 SAA Event Proces

now this output doesn't say much for the 35% cpu utilization shown above. so how to interpret this output.

3.can anyone point out some best practices to protect router's resources against DoS attacks?

thank you


I have this problem too.
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gpulos Mon, 03/05/2007 - 05:54

please see the following link for cisco's response to some of the security threats you may face in IOS:

also, the following link for improving security on IOS routers for your type of attack:

(under the 'secure IP' section)

radiohead23 Tue, 03/06/2007 - 05:23

thank you medan, the info is very helpful. one more it possible to prioritize telnet traffic to the cpu in a router? i know we can police the traffic, but is it possible to prioritize it?


Danilo Dy Tue, 03/06/2007 - 05:46

I haven't tried that in the router and also in the switch. I know that Cisco have traffic prioritization but I'm not sure if it support up to the application level. Wait for the experts to reply :)


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