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Re: Nmap issues...? or router?
From: Josha Bronson <dmuz () slartibartfast angrypacket com>
Date: Sun, 7 Oct 2001 20:48:22 -0700

On Sun, Oct 07, 2001 at 02:39:31AM -0000, bluefur0r bluefur0r said:
After just completeing an audit for a company that has a DS-3
connection (shared) and a cisco router (2015), One of the first issues
that was found was this: When nmaping using -sS and all ports, 1 nmap
scan nmaping 1 host at a time appeared to completely destroy their
bandwidth... Has anyone heard of this? Could this be a Router or ISP
problem??? It took very long to complete because i needed to use the
-T Polite option. I'm just curious if anyone else has ever encountered
nmap using up all network resources for such a high volume connection.
Any help would be appreciated so this never happens again. *Luckily I
started after hours*

Yes, I've seen this before. During and internal audit, one laptop
scaning with nmap brought a LAN router to 100% CPU utilization. I think
that the router had to be rebooted, but I can't remember. The router was
a Cisco, of the 7000 series I believe.

Sorry for the lack of facts, it was a while ago...

I've meant to look into it again and try to pin down exactly what is
going on here, but there never really seems to be a good time to nail a
router that is in use, according to management.

I've also spoken about this with a few other folks who have seen the
same thing.

Anyway, someone with spare time and a test network with a Cisco router
should probably try and figure out what causes this. :)

josha.bronson(aka->dmuz) >> dmuz () angrypacket com
networks/systems/security && CCNA, RHCE 
josha.net || dmuz.angrypacket.com

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