[c-nsp] Redistributing on OSPF

[Tantsura, Jeff]

Why ???

As Oliver already mentioned

External Route Summarization
External route summarization is specific to external routes that are
injected into OSPF via redistribution. Also, make sure that external
ranges that are being summarized are contiguous. Summarization
overlapping ranges from two different routers could cause packets to be
sent to the wrong destination. Summarization is done via the following
router ospf subcommand:

summary-address ip-address mask


This command is effective only on ASBRs doing redistribution into OSPF

Jeff

-----Original Message-----
From: cisco-nsp-bounces at puck.nether.net
[mailto:cisco-nsp-bounces at puck.nether.net] On Behalf Of Piotr Marecki
Sent: Wednesday, January 26, 2005 1:16 PM
To: cisco-nsp at puck.nether.net
Subject: Re: [c-nsp] Redistributing on OSPF


> Hi,
>
> >
> > We are employing OSPF in our Network i.e. 3 locations each of them
in
> > 3 different areas and backbone routers on area 0. now we are having
a
> > problems in Summarizing E1 type of Routes we have employed the area
> > xx range x.x.x.x x.x.x.x command on the ABR but still we are getting
> > Breakup routes like /28 and /29 along with the summarized /24 or /22
> > routes.
> >
> > Can any one of you help me as to how we should go about in
> > summarizing the E1 Routes.
>
> you can't summarize externel routes anywhere in the OSPF network
except
> on the ASBR where you redistribute the routes into OSPF
> (http://www.cisco.com/warp/public/104/1.html#t30).
>
> area xx range <prefix> <mask> does not apply to external OSPF routes.
>
> oli
>

If summarizing routes is top priority there is always possibility to
change
area type to NSSA , where
ABR can summarize/filter during LSA7 to LSA5 translation .Of course not
always NSSA is viable solution ,
all depends on actual topology and network design.

regards

Piotr Marecki

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