Neighbor stuck in Init/DROther state
-------------------------------------
2009/Sep/28 - backlogged
As this is backlogged, it's more as an demonstration rather than 
exact report. Thus figures doesn't have to fit exactly.
I've noticed strange behaviour at one link. This might be for some 
time - two weeks, perhaps. I didn't notice before, because quagga 
in OpenWRT seems to be crapped lately - dropping routes, creating 
loops, etc. So, there was a lot of work and strange stuff going on.


### FIGURE A - ROUTER A ###
rourerA> show ip ospf neighbor 

Neighbor ID     Pri   State           Dead Time   Address         Interface           RXmtL RqstL DBsmL
192.168.0.1        1   Full/DR         00:00:37    192.168.1.33     ath0:192.168.1.34     0     0     0
192.168.0.2        1   Init/DROther    00:00:37    192.168.1.13     ath1:192.168.1.14     0     0     0
192.168.0.3        1   Full/Backup     00:00:37    192.168.1.9      ath2:192.168.1.10     0     0     0
192.168.0.4        1   Full/DR         00:00:32    192.168.1.18     ath3:192.168.1.17     0     0     0
routerA>

routerA> show ip ospf interface ath1
ath1 is up
  Internet Address 192.168.1.14/30, Broadcast 192.168.1.15, Area 0.0.0.0
  Router ID 192.168.0.5, Network Type BROADCAST, Cost: 20
  Transmit Delay is 1 sec, State DROther, Priority 1
  No designated router on this network
  No backup designated router on this network
  Timer intervals configured, Hello 10, Dead 40, Wait 40, Retransmit 5
    Hello due in 00:00:02
  Neighbor Count is 1, Adjacent neighbor count is 0
routerA>
### FIGURE A - ROUTER A ###

### FIGURE B - ROUTER B ###
routerB> show ip ospf neighbor 

Neighbor ID     Pri   State           Dead Time   Address         Interface           RXmtL RqstL DBsmL
192.168.0.1        1   Full/DR         00:00:32    192.168.1.38     ath0:192.168.1.37     0     0     0
192.168.0.3        1   Full/Backup     00:00:33    192.168.1.6      eth0:192.168.1.5     0     0     0
192.168.0.4        1   Full/Backup     00:00:38    192.168.1.1      eth1:192.168.1.2     0     0     0
routerB>

routerB> show ip ospf interface ath1
ath1 is up
  Internet Address 192.168.1.13/30, Broadcast 192.168.1.15, Area 0.0.0.0
  Router ID 192.168.0.2, Network Type BROADCAST, Cost: 20
  Transmit Delay is 1 sec, State DROther, Priority 1
  No designated router on this network
  No backup designated router on this network
  Timer intervals configured, Hello 10, Dead 40, Wait 40, Retransmit 5
    Hello due in 00:00:02
  Neighbor Count is 0, Adjacent neighbor count is 0
routerB>

### FIGURE B - ROUTER B ###

Both routers sent their Hello packets, yet they were unable to "see" 
each other. I've truned on logging at RouterB only to see there is 
some problem with CRC of Hello packets. Log entry looked like:

ospf_check_sum(): checksum mismatch, my AAA, his BBB

This comes from quagga-src/ospfd/ospf_packet.c
I've tried different versions only to get same results. 
Link, where this problem occured, is running stable without any 
probelms.
The fix is easy.
Edit '/etc/quagga/ospfd.conf' at both ends and add following at 
problematic interfaces:

### OSPFD.conf ###
interface ath1
 description link-somewhere
! added line follows
 ip ospf network point-to-point
 ip ospf cost 20
### OSPFD.conf ###

May be there is some problem with transmiting broadcasts, yet it's 
really strange as this problem is unique to one link. Both, RouterA 
and RouterB, routers have N links to other [ospf] routers. No 
problems of such kind. 
I've also tried increase number of IGMP membership:

echo 100 > /proc/sys/net/ipv4/igmp_max_memberships

synchronizing time to every second, but nothing helped. Except 
specifying network type at problematic interfaces. There might be 
problem somewhere in kernel, yet - I don't know.
I hope this will help somebody else :)