[nsp] OSPF NBMA config: frame-relay map vs. static routes

From: Panu Suontausta (panu.suontausta@sonera.com)
Date: Thu Apr 12 2001 - 15:09:14 EDT


Hi,

I have a small Frame Relay hub-and-spoke topology with one hub router
and two spokes. OSPF is running and configured as NBMA, with the hub as
DR as appropriate. I noted that when I configure the spoke routers with
FR map statements for the other spoke router, everything works as
expected (i.e., I can reach the LAN interface of the other spoke from
the other etc.):

interface Serial0
 ip address 10.10.1.3 255.255.255.0
 no ip directed-broadcast
 encapsulation frame-relay
 frame-relay map ip 10.10.1.1 330
 frame-relay map ip 10.10.1.2 330

This Layer 2 mapping solution is the way that every Cisco doc that I can
find suggests.

Out of curiosity, I also tried to do the same thing with static host
routes - statics pointed towards the other spoke router's interface to
the NBMA cloud via the hub router:

interface Serial0
 ip address 10.10.1.3 255.255.255.0
 no ip directed-broadcast
 encapsulation frame-relay
 frame-relay map ip 10.10.1.1 330

ip route 10.10.1.2 255.255.255.255 10.10.1.1

Now the routing table remains unchanged, but e.g., the LAN interfaces in
the spokes are not reachable from each other. Trying to ping, local
router debug says "encapsulation failed". What's the reason this config
fails?

Just playing in the lab...many thanks in advance for helping me enjoy
the Easter holidays. :-)

panu



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