From: Sam Munzani (sam@xxxxxxxxxxx)
Date: Tue Oct 17 2000 - 12:34:24 GMT-3
Comments inline.
> 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
Why are you using "ip ospf network broadcast" on a point-to-point link?
Specially in NBMA it's not a good idea. Leave it to default Point-to-Point.
and it will form adjecency with remote end.
> !
> 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
Again,
If your interface is Point-to-Point why are you using Point-to-Multipoint in
here? Use point-to-point at both ends.
> 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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