BFD with OSPF on NBMA

Lalufu · Thu Mar 10, 2011 9:25 pm

Hi.

I tested this between a RB433 (with 4.16) and a Cisco 1841, but I have a feeling that it would not work between two Mikrotik devices, either.

What I'm trying to do is run OSPF in NBMA mode (there are two UBNT Rockets between the RB and the Cisco, and they eat multicast packets) with BFD, and there seems to be a chicken/egg problem on the Mikrotik side.

Here's the config:

/ip address
add address=192.168.253.73/29 broadcast=192.168.253.79 comment="" disabled=no interface=vlan9 network=\
    192.168.253.72

/routing bfd interface
set all comment="" disabled=no interface=all interval=0.2sec min-rx=0.2sec multiplier=5
add comment="" disabled=no interface=vlan9 interval=0.1sec min-rx=0.1sec multiplier=30

/routing ospf instance
set default comment="" disabled=no distribute-default=if-installed-as-type-1 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=\
    192.168.254.253
/routing ospf area
set backbone area-id=0.0.0.0 comment="" disabled=no instance=default name=backbone type=default
/routing ospf interface
add authentication=md5 authentication-key=keks authentication-key-id=1 comment="" cost=100 dead-interval=2m disabled=\
    no hello-interval=30s instance-id=0 interface=vlan9 network-type=nbma passive=no priority=1 \
    retransmit-interval=5s transmit-delay=1s use-bfd=yes
/routing ospf nbma-neighbor
add address=192.168.253.77 comment="" disabled=no instance=default poll-interval=2m priority=0
/routing ospf network
add area=backbone comment="" disabled=no network=192.168.253.72/29

The config on the Cisco side:

interface FastEthernet0/1
 ip address 192.168.253.77 255.255.255.248
 ip ospf authentication message-digest
 ip ospf message-digest-key 1 md5 keks
 ip ospf network non-broadcast
 ip ospf cost 100
 duplex auto
 speed auto
 bfd interval 100 min_rx 100 multiplier 30
 no bfd echo
 no cdp enable
!
router ospf 1
 mpls ldp sync
 log-adjacency-changes
 passive-interface default
 no passive-interface FastEthernet0/1
 network 192.168.253.72 0.0.0.7 area 0
 neighbor 192.168.253.73
 bfd all-interfaces
!

With this configuration, the OSPF session does not come up, alhough both sides are sending HELLO packets.
The log on the RB show this:

20:22:52 route,ospf,debug   received options: E|R 
20:22:52 route,ospf,debug Ignoring OSPFv2 Hello packet: BFD is not up 
20:22:52 route,ospf,debug     RouterId=192.168.253.245 
20:22:52 route,ospf,debug     source=192.168.253.77

For situations where OSPF learns about it's neighbors via multicast and starts BFD for those neighbors this may be the correct behaviour, but in the NBMA case there is no learning phase, OSPF starts by sending unicast packets.

I think this is a bug, unless I'm missing somethings.

Thoughts? Thanks.