From: mannan venkatesan (venkat_m@xxxxxxx)
Date: Tue Oct 17 2000 - 12:07:26 GMT-3
Hi,
I was playing in ospf over FR lab and came across an interesting problem(I
was trying to simulate the problem we had in our client production network).
I configured R1 as hub (sub-ifs) and R2 and R3 as spoke (physical
interface). Here the config,
R1 :
interface Serial0.1 point-to-point
ip address 10.1.0.1 255.255.0.0
ip ospf network broadcast
frame-relay interface-dlci 100
!
interface Serial0.2 point-to-point
ip address 10.2.0.1 255.255.0.0
ip ospf network Point-to-multipoint
frame-relay interface-dlci 103
router ospf 10
network 10.0.0.0 0.255.255.255 area 0
R2 :
interface Serial0
ip address 10.1.0.2 255.255.0.0
encapsulation frame-relay
ip ospf network Point-to-multipoint
frame-relay map ip 10.1.0.1 106
router ospf 10
network 10.0.0.0 0.255.255.255 area 0
R3:
interface Serial0
ip address 10.2.0.2 255.255.0.0
encapsulation frame-relay
ip ospf network Point-to-multipoint
frame-relay map ip 10.2.0.1 106
router ospf 10
network 10.0.0.0 0.255.255.255 area 0
It worked fine with this config. Then I changed OSPF network type to
"Broadcast" in s0 of R3 and s0.2 of R1. R3 became DR and R1 became BDR.
After I changed OSPF network type to "Broadcast" in s0.1 of R1 and s0 of R2.
As soon as I entered network type 'broadcast' in R2, the network broke. I
couldn't access any of the routers for 5 minutes.
Now 'sh ip ospf nei' command shows,
R1:
Neighbor ID Pri State Dead Time Address Interface
10.1.0.2 1 FULL/BDR 00:00:39 10.1.0.2 Serial0.1
10.2.0.2 1 FULL/BDR 00:00:37 10.2.0.2 Serial0.2
R2:
Neighbor ID Pri State Dead Time Address Interface
10.2.0.1 1 FULL/DR 00:00:31 10.1.0.1 Serial0
R3:
Neighbor ID Pri State Dead Time Address Interface
10.2.0.1 1 FULL/DR 00:00:39 10.2.0.1 Serial0
I know DR and BDR election was going on, but why the network broke? During
election, routers multicast packets and we have only 3 routers. So, what
traffic did the routers send here? Can I have multiple OSPF network in one
broadcast medium? Can someone clarify my questions? Think I am missing
something here.
Thanks,
Mannan Venkatesan
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