Hey All,

Building our first stub areas. Here is the issue:

I have defined 2 areas on my ABR, Backbone and Border. Backbone is working just fine but the Border area is behaving oddly.

Full config is below, but here is a summery:

Border is a Stub area, it is configured for broadcast. Both routers see each other as neighbors (the entire setup has 2x ABR and 6 Edge devices, but for simplicity i choose to focus on only one ABR and on edge device).

Even though they see each other as neighbors they do not exchange routes, edge does not get a default route and ABR does not get any routes from the Edge. But if i change the network type to Point to Point, all the sudden the edge gets default route and all connected routes from ABR and ABR gets routes from Edge.

As i said i have many devices on the interface from the ABR and there for cannot use Point to Point.

Why does Point to Point allow the routers to exchange routes as expected while Broadcast does not? im running 4.16 on both devices.

ABR 1:

/routing ospf export
# jan/26/2011 23:08:01 by RouterOS 4.16
# software id = XXXXXXXXX
#
/routing ospf instance
set default comment="" disabled=no distribute-default=never in-filter=ospf-in metric-bgp=auto metric-connected=20 metric-default=1 metric-other-ospf=auto metric-rip=\
20 metric-static=20 name=default out-filter=ospf-out redistribute-bgp=no redistribute-connected=as-type-1 redistribute-other-ospf=no redistribute-rip=no \
redistribute-static=as-type-1 router-id=10.254.254.205
/routing ospf area
set backbone area-id=0.0.0.0 comment="" disabled=no instance=default name=backbone type=default
add area-id=0.0.0.1 comment="" default-cost=1 disabled=no inject-summary-lsas=yes instance=default name=Border type=stub
/routing ospf interface
add authentication=md5 authentication-key="something" authentication-key-id=1 comment="" cost=1 dead-interval=40s disabled=no hello-interval=10s instance-id=0 \
interface=ether2 network-type=point-to-point passive=no priority=1 retransmit-interval=5s transmit-delay=1s use-bfd=no
add authentication=md5 authentication-key="something" authentication-key-id=1 comment="" cost=1 dead-interval=40s disabled=no hello-interval=10s instance-id=0 \
interface=ether1 network-type=point-to-point passive=no priority=1 retransmit-interval=5s transmit-delay=1s use-bfd=no
add authentication=md5 authentication-key="something" authentication-key-id=1 comment="" cost=1 dead-interval=40s disabled=no hello-interval=10s instance-id=0 \
interface="BW to XXXX VLAN 11" network-type=point-to-point passive=no priority=1 retransmit-interval=5s transmit-delay=1s use-bfd=no
add authentication=md5 authentication-key="something" authentication-key-id=1 comment="" cost=10 dead-interval=40s disabled=no hello-interval=10s instance-id=0 \
interface="DW to XXX on vlan 20" network-type=point-to-point passive=no priority=1 retransmit-interval=5s transmit-delay=1s use-bfd=no
add authentication=md5 authentication-key="something2" authentication-key-id=1 comment="" cost=100 dead-interval=40s disabled=no hello-interval=10s instance-id=0 \
interface="vlan 800" network-type=broadcast passive=no priority=1 retransmit-interval=5s transmit-delay=1s use-bfd=no
/routing ospf network
add area=backbone comment="" disabled=no network=10.205.0.252/30
add area=backbone comment="" disabled=no network=10.205.0.248/30
add area=backbone comment="" disabled=no network=10.250.0.160/30
add area=backbone comment="" disabled=no network=10.205.0.196/30
add area=Border comment="" disabled=no network=10.205.100.32/27

Edge router 1:

/routing ospf export
# jan/26/2011 23:29:05 by RouterOS 4.16
# software id = XXXXXXXX
#
/routing ospf instance
set default comment="" disabled=no distribute-default=never in-filter=ospf-in metric-bgp=auto metric-connected=20 \
metric-default=1 metric-other-ospf=auto metric-rip=20 metric-static=20 name=default out-filter=ospf-out \
redistribute-bgp=no redistribute-connected=as-type-1 redistribute-other-ospf=no redistribute-rip=no \
redistribute-static=as-type-1 router-id=10.205.100.34
/routing ospf area
set backbone area-id=0.0.0.0 comment="" disabled=no instance=default name=backbone type=default
add area-id=0.0.0.1 comment="" default-cost=1 disabled=no inject-summary-lsas=no instance=default name=Border \
type=stub
/routing ospf interface
add authentication=md5 authentication-key="something2" authentication-key-id=1 comment="" cost=100 dead-interval=\
40s disabled=no hello-interval=10s instance-id=0 interface=ether1 network-type=broadcast passive=no priority=1 \
retransmit-interval=5s transmit-delay=1s use-bfd=no
/routing ospf network
add area=Border comment="" disabled=no network=10.205.100.32/27

What could be the issue?

Regards,

Martin

note to one self, keep track of MTU sizes across the network.

It seems that the MTU of the VLAN connecting to the Edge / Backbone was mismatched 9500 vs. 9200 with a switch in the middle doing 9198. Made everything 9198 and issue is gone.

Guess the router fits as many LSA's into a single frame as possible after neighbor relationships are established via Hello.