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Re: spare swamp space?

  • From: Jason Lixfeld
  • Date: Fri Aug 21 14:38:11 1998

I've got it up on 3 7206s as global options (meaning it is automatically
introduced to all interfaces) and it dropped my CPU by 3 points.

On Wed, 19 Aug 1998, Alex Bligh wrote:

:Steve,
:
:> I too have a similar setup for my network since we as well
:> run an Efnet irc server, however, CAR really won't do much if
:> you set it up inside your own network.  The smurf will still enter
:> and saturate your pipes.  The best thing to do is to have your upstreams
:> setup rate-limits on their side of your pipes so the feed coming into your
:> router is limited before it even hits your router.
:> 
:> Here is a question though,  what kind of CPU drain does rate-limiting cause
:> on the CPU of the routers running it? I flipped through CCO and couldn't find
:> any information regarding this...
:
:My limited experience is that if you run CEF on the interface concerned,
:life is bearable. If you don't, it isn't. If you run < 11.1.17?? CA
:where fast discards and routes to null0 were introduced, life is
:disastrous.
:
:Alex Bligh
:GX Networks (formerly Xara Networks)
:
:> 
:> 
:> Alex Bligh wrote:
:> 
:> > > servers, one for the outside world and one for our customers only.  The
:> > > public server will be connected via a T1 to a smurf tracing friendly
:> > > transit provider for external connectivity.  This T1 will be used for this
:> >
:> > OK, tell me where this falls down. Set up two IP addresses for your
:> > IRC server on the same machine. On the router upstream from the machine,
:> > allow only your customers to connect to one IP address, and anyone else
:> > to connect to the other IP. Now go to your border routers, enable CEF
:> > and configure something like:
:> >
:> > ! impose limits
:> > access-list 100 permit ip any host public-irc.my.net
:> > access-list 100 permit ip any host public-irc.my.net
:> > access-list 101 deny ip any host private-irc.my.net
:> > ! i/f config for borders
:> > interface myinterface
:> >  ip access-group 101 in
:> >  rate-limit input access-group 102 512000 512000 512000 conform-action transmit exceed-action drop
:> >
:> > Effectively this means that if your public IP gets smurfed, it's b/w
:> > usage internally on your network is limited. If your private IP gets
:> > smurfed, it all gets dropped (thinking about it if you made exceptions
:> > for IRC peering you could do the whole thing on one IP if your customers
:> > never use border router i/fs).
:> >
:> > If you are paying per bit, you'll still pay for smurfs, but they'll have
:> > to be 45Mb/s in size to cause any real damage. You'll probably find BGP
:> > flapping up and down as your T1 saturates is more of a problem.
:> >
:> > --
:> > Alex Bligh
:> > GX Networks (formerly Xara Networks)
:> >
:> >
:> 
:> --
:>                               \\|//
:>                              -(@ @)-
:> ==========================oOO==(_)==OOo=================================
:> Steven Nash                            uin: 9021398
:> Cisco Certified Design Specialist       em: snash@lightning.net
:> Network Engineer
:> Lightning Internet Services LLC
:> http://www.lightning.net
:> -=+===================================================================+-
:> 
:> 
:> 
:
:

--
Regards,  

Jason A. Lixfeld

Network Engineer, iDirect Network Operations

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