Re: redistribution bgp>ospf

Hey Joseph

The way im doing this is ospf>bgp by using network statements that's a
given...

My problem is I don't know the full source address from BGP hence need ospf
to know outbound routing...

So with a small test im redistributing bgp>ospf and it's not mutual as
above, im tagging the bgp>ospf with the ebgp AS number and seeing the
correct amount of routes in the ospf rib on the internal devices

On Marc's point we're and end AS so not sure 100% if I can be used as
transit here..

We have two CE's which are meshed ibgp and peering to the same ebgp AS

Thanks

Tony

On 24 February 2013 17:32, Joseph L. Brunner <joe_at_affirmedsystems.com>wrote:

> Is this one Physical Location the ONLY location where your routes are
> actually being announced in the whole internet Tony?
>
> I would not do the ospf<->bgp redistribute thing - I would just throw a
> few static routes to "null0 254" into my router and use bgp network
> statements under the process to announce them. Why?
>
> Because why add risk and overhead when you don't need to?
>
> The ONLY time I would EVER redistribute ospf (or any igp) into bgp running
> with a carrier is *IF* I had several other ways out of my network and my
> network had private/internal networking between the places where I speak
> bgp - kind of like a huge company with datacenters in NYC and San Fran,
> etc. but the inside is connected via Fiber, MPLS, etc.
>
> Now, the redistribution of OSPF <-> BGP buys me:
>
> 1. My ospf network will use the "closest" exit point - via using E1
> metrics to carry the hop by hop cost of taking the exit they find to the
> Internet...
> 2. My bgp edge network will advertise routes to the WHOLE internet it can
> actually get to - and wont advertise them out when it can't get there - say
> that FIBER between my coasts is down.
>
> In tribute to the great Jimi Hendrix, I call this design "There must be
> some kind of way out of here".
>
> -Joe
>
> -----Original Message-----
> From: nobody_at_groupstudy.com [mailto:nobody_at_groupstudy.com] On Behalf Of
> Tony Singh
> Sent: Sunday, February 24, 2013 7:23 AM
> To: Cisco certification
> Subject: redistribution bgp>ospf
>
> Hi
>
> Just a quick sanity check...
>
> I'm redistributing bgp>ospf and using network statements to control how my
> ospf subnets are sent to my ebgp peer, now please correct my understanding
> but the ebgp peer see's the ospf routes coming from my AS number...and when
> I reset this connection I can see in debug ip bgp updates the update
> message for the original ospf routes when the ebgp peers synchronize will
> deny my originated prefixes coming back to due to = DENIED due to: AS-PATH
> contains our own AS;
>
> So therefore there is no risk if I redistribute bgp into ospf of double
> redistribution as the ebgp boundary would deny any originally originated
> prefixes in the first instance?
>
> in summary, I am using network statements to control ospf>bgp and bgp>ospf
> is using redistribute keyword with tag<as number> and I can see in ospf rib
> on internal devices only the tagged prefixes which I would expect.
>
> I have seen some examples using bgp community to tag & deny but this is
> only when using mutual redistribute command under both processes.
>
> Best Regards
>
> Tony
>
>
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Received on Sun Feb 24 2013 - 17:41:49 ART