From: Sandro Ciffali (sandyccie@xxxxxxxxx)
Date: Mon Mar 18 2002 - 09:47:00 GMT-3
John,
Jeff Doyle Vol2 has a case study explaining the table maps, They are used
for the following conditions.
Let us say you are a transit AS and you do not run IBGP beween your AS
border routers. You rely completly on redistributing Ebgp learnt routes at
the border in redistributing them into IGP and then at the other end
redistributing IGP into EBGP again to give it to the next AS. There are BGP
attributes like originating AS, AS-Path, origin code, community etc. etc.
which will get lost in the process.
If you want to preserve all the above attributes, you got to use table map.
On the EBGP peer redistributing Ebgp into IGP create a route-map which maps
all the routes learnt by the ebgp peer, and set automatic-tag. This creates
an automatic tag that contains all the bgp info about the network. This
route-map is then applied as a table map under bgp.
Apply the similar table map under bgp process on the other end while
redistributing igp into Ebgp to get the bgp attrobutes back from the tag.
I do not know how much mature this solution is yet, I tried this couple of
days back using eigrp as my IGP, It never worked, Then i change my IGP as
OSPF (just like Doyle case study) now i got my as and as-path info back
however all the networks that were i before are now seen as e, But the ?
routes are fine.
Hope this helps.
Sandro
----- Original Message -----
From: "John Neiberger" <neiby@ureach.com>
To: <ccielab@groupstudy.com>
Sent: Sunday, March 17, 2002 11:24 PM
Subject: Table Maps
> Can someone please explain how table maps operate and the
> problem they are designed to solve? They are mentioned a
> handful of times in the lab list archives but those posts
> weren't very explanatory.
>
> On CCO, so far I've only found some info on QoS propagation
> through BGP and wasn't able to figure what exactly they were
> trying to accomplish, but perhaps I need to look a little more
> closely.
>
> In what type of situation would I want or need to use a table
> map?
>
> Thanks,
> John
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