From: dszarmach (dszarmach@comhs.org)
Date: Fri Dec 30 2005 - 12:16:01 GMT-3
With redistribution I remember reading a good rule somewhere:
"Never tell others about a route that you aren't using yourself"
-
Doug
________________________________
From: nobody@groupstudy.com on behalf of Bob Sinclair
Sent: Fri 12/30/2005 8:22 AM
To: Schulz, Dave; ccielab@groupstudy.com
Cc: Cisco certification
Subject: Re: Simple redistribution question
Dave,
Simple answer to a simple question: routes are redistributed because they
are
in the table via the source protocol, not because they are in the database of
the source protocol.
This can be tested on a router with three protocols, For example, RIP and
OSPF
into EIGRP. Suppose both the RIP and OSPF domains have the same prefix and
you vary the metrics as you redistribute RIP and OSPF into EIGRP. You should
see the routes from OSPF by default. Lower the AD for RIP to 109, and you
should see the metric for the RIP redistribution in EIGRP. Surely changing
the AD does not change the routes in the local database.
HTH,
Bob Sinclair
CCIE #10427, CCSI 30427
www.netmasterclass.net
----- Original Message -----
From: Schulz, Dave
To: Brian Dennis ; nobody@groupstudy.com ; ccie2k4 ; J. Holmes
Cc: Cisco certification
Sent: Friday, December 30, 2005 8:57 AM
Subject: RE: Simple redistribution question
Does redistribution take place because a route is in the routing table, or,
because the route is in the database for the protocol that is being
redistributed?
Dave
-----Original Message-----
From: nobody@groupstudy.com
To: ccie2k4; J. Holmes
Cc: Cisco certification
Sent: 12/27/2005 3:41 PM
Subject: RE: Simple redistribution question
To figure out why it doesn't work the way you explain below lets see
what would happen if it did work that way.
We'll say the local router is R1 and network in question is the
10.0.0.0/8 network learned via RIP from R2. R1 is running RIP and OSPF.
The RIP route (10.0.0.0/8) is redistributed into OSPF on R1. As per
your explanation below it now shows up in R1's routing table as an
external OSPF route by overtaking the RIP route due to the lower
administrative distance of OSPF.
Here in lies the problem. Since the RIP route that told R1 to reach the
10.0.0.0/8 via R2 is now not in the routing table, how would R1 know how
to reach the 10.0.0.0/8 network? Also since the 10.0.0.0/8 RIP route is
not in the routing table via RIP it can not be redistributed into OSPF.
This should explain why redistribution works the way I stated in an
earlier e-mail on this topic.
HTH,
Brian Dennis, CCIE #2210 (R&S/ISP-Dial/Security)
bdennis@internetworkexpert.com
Internetwork Expert, Inc.
http://www.InternetworkExpert.com
Toll Free: 877-224-8987
Direct: 775-745-6404 (Outside the US and Canada)
-----Original Message-----
From: nobody@groupstudy.com [mailto:nobody@groupstudy.com] On Behalf Of
ccie2k4
Sent: Tuesday, December 27, 2005 12:00 PM
To: J. Holmes
Cc: Cisco certification
Subject: Re: Simple redistribution question
Hi All,
Maybe I haven't quite understood the original question completely but
wouldn't the route show up as an OSPF route once its redistributed from
RIP
to OSPF on the router performing mutual redistribution hence leading to
a
loop. My thinking over here is based on the fact that OSPF has a lower
admin
distance than RIP hence it should overwrite the RIP route in the table.
Please correct me if I am incorrect on this. Thanks
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