RE: [Flow-tools] Strange Router Export Issue

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Subject: RE: [Flow-tools] Strange Router Export Issue
Greg.Volk@edwardjones.com
Date: Thu May 19 2005 - 12:54:27 CDT

>
>I’ve got a strange issue that is just perplexing me. Basically 
>here’s my setup:
>
>I’ve got two 7513’s and one 7206. Each has one internet DS-3. The 
>7513’s also support other customer connections, but the 7206 is just 
>the DS-3. 
>
>Starting a couple of days ago, the 7206 started sending HUGE numbers 
>(10x normal) of flows to my flow-collector. I’ve dug into the raw 
>flow files and I just don’t see anything strange. All three routers 
>carry about the same traffic load according to bandwidth, but the 
>flows are out of the ball park for the 7206. It’s almost like the 
>router is counting traffic multiple times, but the config didn’t 
>change when this started.
>
>
>Anyone have any ideas on where I should look?
>

This sounds like a ddos attack to me. I've been hit with a ddos 
before on my internet router which happens to be a 7206VXR with a 
full DS3 attached to it. It added about 20% onto the router's CPU 
utilization and drove up the number of flows by at least 10x. The 
additional flows caused my flow-capture/flowscan system to fall 
behind to the point that I had to kill flow-capture until the ddos 
was over.




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