From: ccie2be (ccie2be@nyc.rr.com)
Date: Mon Jul 28 2003 - 09:38:47 GMT-3
Hi,
I'd like to verify something. It seems to me that when doing redist between
routing protocols which tagged redistributed routes as External, like OSPF and
Eigrp, it's not necessary to configure route filters to prevent routes which
have been redist from being redist back into the their original routing
protocol.
For example, if the following topology exists
EIGRP domain
---------R1-----------------R2-------------
OSPF domain
and 2-way redistribution is configured at both R1 and R2, there's no need for
route filters because an OSPF route which is redist by R1 into the Eigrp
domain is marked as External and therefore will not be redistributed back
into the OSPF domain at router R2. In other words, routers doing redist, by
default, filter routes tagged as External. What I'd like to confirm is that
this is true in all cases, not just the ones I've come across ( I've done 2 or
3 practice labs where this was true).
Also, I'd like to confirm that if the above is true, then the following is
also true.
RIP domain
---------R1-----------------R2-------------
Eigrp domain
In this situation, route filters are only needed when redist RIP into Eigrp on
R1 and R2 because when an Eigrp is redist into RIP, RIP doesn't distinquish
between "native" RIP routes and routes redist into RIP and therefore would
redist those routes back into the Eigrp domain unless a route filter were
configured to prevent that.
I'm hoping someone in Group Study will either confirm this theory or debunk it
and explain why this is true or false.
Thanks in advance, Raj
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