From: Justin Menga (Justin.Menga@xxxxxxxxxxxxxxxxxx)
Date: Mon Oct 30 2000 - 17:35:09 GMT-3
When you are using point-to-point subinterfaces, you must use different IP
subnets for each hub<->spoke point-to-point link. Thus, there is no way
that two spoke routers can become adjacent.
Even if you moved your frame network to a single IP subnet with NBMA or
point-to-multipoint, the spoke routers should never become adjacent, as in
OSPF, adjacencies are only formed with the DR (NBMA), which should be the
hub router (you could have one of the spokes as a BDR, and then spoke
routers would form adjacencies with the BDR, however this is functionally
useless because if the hub router (DR) fails, you won't be able to
communicate with the BDR).
If you do use a single subnet, I recommend setting the OSPF priority on
spoke routers to 0 on their serial interfaces. This prevents them from
becoming DR/BDR on the NBMA network, and forces the hub router to always be
the DR.
Regards,
Justin Menga MCSE+I CCNP CCSE ASE
WAN Specialist
Computerland New Zealand
PO Box 3631, Auckland
DDI: (+64) 9 360 4864 Mobile: (+64) 25 349 599
mailto: justin.menga@computerland.co.nz
-----Original Message-----
From: Jobson, Ed [mailto:ejobson@thrupoint.net]
Sent: Tuesday, 31 October 2000 2:01 p.m.
To: ccielab@groupstudy.com
Subject: OSPF NBMA question
I have 3 routers set up in a Frame Relay hub and spoke layout, all using
point-to-point subinterfaces and manual dlci's. I have full IP connectivity
between the 3 and they are in OSPF area 0 all with 10 second default
point-to-point OSPF hello intervals. So connectivity is fine but the two
spoke routers do not form OSPF adjacencies. Is that correct or would I loose
marks for that? If so is there a way of getting spokes adjacent by changing
the interface type to multipoint or something? But I must stick to
point-to-point subinterfaces with manual dlci's?
Thanks, configs below.
Eddie.
HUB
R2
interface Serial1.1 point-to-point
ip address 137.1.7.17 255.255.255.252
frame-relay interface-dlci 103
!
interface Serial1.2 point-to-point
ip address 137.1.7.21 255.255.255.252
frame-relay interface-dlci 105
SPOKE1
R3
interface Serial0/0.1 point-to-point
ip address 137.1.7.18 255.255.255.252
frame-relay interface-dlci 103
SPOKE2
R5
interface Serial1.1 point-to-point
ip address 137.1.7.22 255.255.255.252
frame-relay interface-dlci 105
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