From: Colin Barber (Colin.Barber@telewest.co.uk)
Date: Sun Sep 08 2002 - 07:32:33 GMT-3
In OSPF you have the discard-route command. The question is why would you
want to remove these routes, unless asked to in a lab scenario? They are
generated to avoid possible routing loops. Okay your summary may not cause a
routing loop at the time you generate it but what about in 6 months time,
will you remember to update your routers?
I would always recommend keeping the automatically generated summaries to
null0, and if your IOS is not generating them then add static routes.
Colin
-----Original Message-----
From: Armand D [mailto:ciscoworks2001@yahoo.com]
Sent: 08 September 2002 06:49
To: Blanco Lam; Chris Hugo
Cc: ccielab@groupstudy.com
Subject: Re: Null Routes- And when it's safe to remove
How do you remove it ?
--- Blanco Lam <b@gclamb.com> wrote: > I think it's
safe to remove the null route.
>
> Without the default route, when routerb receives
> anything that's not in its
> routing table, it should just drop it.
>
> ---- Original message ----
> >Date: Sat, 7 Sep 2002 03:37:52 -0700 (PDT)
> >From: Chris Hugo <chrishugo@yahoo.com>
> >Subject: Null Routes- And when it's safe to remove
>
> >To: ccielab@groupstudy.com
> >
> >Hi Folks,
> >
> >I have a quick question that somebody can probably
> clarify in a heartbeat.
> >
> >Let's say you have two routers:
> >
> >routera------routerb
> >
> >routerb has the following routes in it's routing
> table:
> >
> >192.168.100.0/24
> >
> >192.168.200.0/24
> >
> >192.168.300.0/24
> >
> >Now on routerb I want to create A summary route
> using any IGP routing
> protocol.
> >
> >The summary route is:
> >
> >192.168.0.0/16
> >
> >By default a routing protocol will summarize that
> route and propagate the
> summarized route.
> >
> >Now what also happens is a null route is also from
> that specific routing
> protocol into the router that originated the route.
> Of course this makes cent$
> to avoid a routing loop.
> >
> >Now if routerb has a default route to router and
> routerb happens to lose ONE
> route to 192.168.1.0 a routing loop will easily form
> without a null route on
> routerb to 192.168.0.0.
> >
> >OK, now let's eliminate the default route on
> routerb but the summary route is
> still propagated from routerb. Is it totally safe to
> say I can remove the
> summary route without creating Possible routing loop
> if one route happens to
> fail. I know how to remove this route that is not my
> concern.
> >
> >I want to know if it is safe to remove this null
> route in this condition....
> >
> >Thank U..
> >
> >chris hugo
> >
> >
> >
> >
> >
> >---------------------------------
> >Do You Yahoo!?
> >Yahoo! Finance - Get real-time stock quotes
>
This archive was generated by hypermail 2.1.4 : Mon Oct 07 2002 - 07:43:46 GMT-3