Re: Using Policy Routing to stop DoS attacks

["Christopher L. Morrow" <chris () UU NET>]

On Fri, 28 Mar 2003, Andre Chapuis wrote:

> We could ask Cisco and Juniper to add a way of 'artificially' remove
> networks from the CEF table (with an ACL or so). That way, even with
> loose-RPF, the packet will be dropped based on source-address at the
> ingress without consuming CPU.

Keep in mind that this functionality would still be held to the same set
of restrictions as uRPF... and you CAN accomplish this with a blackhole
setup on your network. By blackholing source prefixes you COULD get this
same effect.

> Or maybe such a feature already exist

it kind of does... though with some real routing goo, not via an acl.

> Andr?
>
> At 09:06 25.03.2003 -0500, Christian Liendo wrote:
>
> > Looking for advice.
> >
> > I am sorry if this was discussed before, but I cannot seem to find this.
> > I want to use source routing as a way to stop a DoS rather than use access-lists.
> >
> > In other words, lets say I know the source IP (range of IPs) of an attack and they do not change.
> >
> > If the destination stays the same I can easily null route the destination, but what if the destination constantly 
> > changes. So I have to work based on the source IP.
> >
> > Depending on the router and the code, if I implement an access-list then the CPU utilization shoots through the roof.
> > What I would like to try and do is use source routing to route that traffic to null. I figured it would be easier on 
> > the router than an access-list.
> >
> > Has anyone else tried this successfully on ciscos and junipers?
> > Is it easier on the CPU than access-lists?
> > Is there a link I cannot find on cisco or google?
> >
> > Thanks
> > Christian Liendo
>
> ---------------------
> Andre Chapuis
> IP+ Engineering
> Swisscom Ltd
> Genfergasse 14
> 3050 Bern
> +41 31 893 89 61
> chapuis () ip-plus net
> CCIE #6023
> ----------------------