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Router Flooding Interface

 
 
Matt
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      07-10-2003
Is it normal for this to happen?

Upstream provider routs IPs to me.
I don't put a route in my router for those IPs.
My pipe gets flooded by traffic going around in circles between my
upstream and me.

Is that normal? Shouldn't my router just drop and ignore the traffic
if there is no default rout in for it and it's INCOMING?

 
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Barry Margolin
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      07-10-2003
In article <3f0dc6e4$(E-Mail Removed)>, Matt <(E-Mail Removed)> wrote:
>Is it normal for this to happen?
>
>Upstream provider routs IPs to me.
>I don't put a route in my router for those IPs.


Why not? Add a null0 route if you don't have a place to send them at the
moment.

>My pipe gets flooded by traffic going around in circles between my
>upstream and me.
>
>Is that normal? Shouldn't my router just drop and ignore the traffic
>if there is no default rout in for it and it's INCOMING?


No. Sometimes it's correct for packets to go back out the same interface
they came in on. Most of these cases happen on LANs rather than serial
interfaces, but the forwarding decisions are made without taking into
account the type of interface.

--
Barry Margolin, http://www.velocityreviews.com/forums/(E-Mail Removed)
Level(3), Woburn, MA
*** DON'T SEND TECHNICAL QUESTIONS DIRECTLY TO ME, post them to newsgroups.
Please DON'T copy followups to me -- I'll assume it wasn't posted to the group.
 
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Michael T. Hall
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      07-11-2003
With few exceptions, perimeter routers should always have a static route to
null0 for the set of all IP addresses under private control. Set the static
route to a high administrative distance, which will cause the route to serve
as a safety net. So, if one of your internal routes disappears from the
perimeter routing table, packets will drop. Otherwise, internal traffic can
cause congestion on your outside link (exactly like you're describing).

Michael


"Barry Margolin" <(E-Mail Removed)> wrote in message
newsUjPa.88$(E-Mail Removed)3.com...
> In article <3f0dc6e4$(E-Mail Removed)>, Matt <(E-Mail Removed)> wrote:
> >Is it normal for this to happen?
> >
> >Upstream provider routs IPs to me.
> >I don't put a route in my router for those IPs.

>
> Why not? Add a null0 route if you don't have a place to send them at the
> moment.
>
> >My pipe gets flooded by traffic going around in circles between my
> >upstream and me.
> >
> >Is that normal? Shouldn't my router just drop and ignore the traffic
> >if there is no default rout in for it and it's INCOMING?

>
> No. Sometimes it's correct for packets to go back out the same interface
> they came in on. Most of these cases happen on LANs rather than serial
> interfaces, but the forwarding decisions are made without taking into
> account the type of interface.
>
> --
> Barry Margolin, (E-Mail Removed)
> Level(3), Woburn, MA
> *** DON'T SEND TECHNICAL QUESTIONS DIRECTLY TO ME, post them to

newsgroups.
> Please DON'T copy followups to me -- I'll assume it wasn't posted to the

group.


 
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