[c-nsp] DDOS, router acted "oddly".

[Drew Weaver]

More information, the traffic they sent looked like this:

1188461504.873821 y.y.y.y -> x.x.x.x UDP Source port: 45362  Destination port: 11067[Malformed Packet]

0000  00 18 8b 4e bf df 00 05 dd 27 58 40 08 00 45 00   ...N.....'X at ..E.
0010  00 1d 00 00 40 00 38 11 94 c9 c1 1b 56 c5 d1 33   .... at .8.....V..3
0020  c4 f2 b1 32 2b 3b 00 09 45 67 30 00 00 00 00 00   ...2+;..Eg0.....
0030  00 00 00 00 00 00 00 00 00 00 00 00               ............

-----Original Message-----
From: cisco-nsp-bounces at puck.nether.net [mailto:cisco-nsp-bounces at puck.nether.net] On Behalf Of Drew Weaver
Sent: Thursday, August 30, 2007 9:52 AM
To: cisco-nsp at puck.nether.net
Subject: [c-nsp] DDOS, router acted "oddly".

        I believe I know why I had the issue I had last evening when a 500Mbps DDOS hit our network. I believe it is due to queuing issues, but I am not sure, I wanted to ask you folks what you thought.

The topology of the 'attack ' is as such:

Attacker - Internet - 3Gbps aggregate(4 connections) - 2x Cisco GSR 12000 - 4x Gig-E - Catalyst 6509 - 100Mbps -- target host

So last evening we were hit with a 500Mbps DDOS attack, this shouldn't have been a big deal as we have over 3Gbps in aggregate bandwidth and this 500Mbps pushed our total utilization up to around 1300Mbps. However, we noticed that the DDOS was degrading connectivity for all hosts on the network.

* The (multiple) gig-e connections between the GSRs and the Catalyst 6509 were nowhere near their maximum capacity
* I see no errors in the log files of either of the two GSRs which were involved
* The 100Mbps port which the target host was connected to was obviously pegged.
* There were no errors logged on that particular catalyst (although I believe the problem is obviously with the GSRs)

I don't really see any "good?" reason why all of the traffic flowing through both of the GSR 12ks would have been reduced to a crawl unless there was some kind of queue backlash between the Catalyst and the GSR 12ks.

Does anyone have any advice or insight?

Thanks,
-Drew

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