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RE: Frame Relay and OSPF - Next Hop Confusion posted 06/30/2004
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Take a look at the "show frame map" and see if you have some extra
reachability that you shouldn't have.  Perhaps your router thinks
differently than you do!  (I hate when they do that!)

 
Scott Morris, CCIE4 (R&S/ISP-Dial/Security/Service Provider) #4713, CISSP,
JNCIP, et al.
IPExpert CCIE Program Manager
IPExpert Sr. Technical Instructor
swm@xxxxxxxxxx/smorris@xxxxxxxxxxxx
http://www.ipexpert.net
 
 

-----Original Message-----
From: nobody@xxxxxxxxxxxxxx [mailto:nobody@xxxxxxxxxxxxxx] On Behalf Of
Andrew Lissitz
Sent: Tuesday, June 29, 2004 8:21 PM
To: 'ccielab@xxxxxxxxxxxxxx'
Subject: Frame Relay and OSPF - Next Hop Confusion

First; I must say hello to everyone, and thanks for the great effort many of
you have put into your postings.  I have learned a lot from everyone. 

 

Second; hello Scott Morris and the IPExpert class of May 2004.  You all
taught me a lot as well.  Scott is sure to be routing diapers and honey-do
lists by now... perhaps there is a CCIE in re-routing requests to change
diapers and ... never mind ... his administrative distance is sure to be
higher than his wife's.  Bummer dude - I am in the same boat!

 

Third; my question to you all:

 

In my lab I have configured a frame relay network with multipoint
interfaces.  I am following a lab given by the IPExpert class.   The setup
has 1 core router and two remotes.  The routers are sharing the same address
space.

 

The core is configured with 1 multipoint sub interface.  The remotes are
configured to use serial 0.  There are no connectivity problems between the
remotes and cores.  There is however a problem when pinging from one remote
to another.  

 

It seems that the remotes think that each other are directly connected.
When I send a ping from a remote I saw that the core router would send an
ICMP redirects informing the remote router to connect directly.  It seems
that the routers think they are fully meshed when in fact they are not.  

 

I turned off icmp redirects @ the core but this did not help.  I would then
get an encapsulation failed message, so I added a frame map command.  This
did not help since the remotes think that they can reach each other directly
and that they do not need to go through the core.  I rebooted the routers
and they still believe themselves to be fully meshed.

 

The routing table also shows the networks located off of the remotes as
being reached via a next hop of each other.  Again, they are not fully
meshed so they can not get to each other directly and the routing of packets
fail.

 

How do I tell the routers that they are not installed in a full mesh?  

 

OSPF seems to believe the routers are fully meshed as well.

 

Please keep in mind that the lab does not allow for sub interfaces on the
remotes.  It also does not allow for OSPF network type commands.  I have
configured neighbor statements with priorities for the remotes.  I have
tried every combination of neighbor statement while always ensuring that the
core is the DR with the highest priority.

 

Another note related to OSPF:

 

There is redistribution of OSPF into RIP and RIP into OSPF @ two different
places (I know this is ugly but the lab says to do it...)  The
redistribution places are not these routers, and occurring on different
routers in my setup, although the redistributed networks are being
propagated to these routers via OSPF.  The core router is receiving these
updates.   Is this related?  

 

Any thoughts you all?  Thanks in advance for the responses and
consideration.  Kindest regards, 

 

Andrew Lissitz

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