OSPF interval value mismatch

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Article ID: 167879

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Updated On:

Products

XOS

Issue/Introduction

OSPF routers cannot form neighbor relationship due to a mismatch in Hello or Dead parameters.OSPF adjacency cannot be established with a neighbor router and mismatch in Hello or Dead parameter values is suspected. 
User-added image

ospfd#show ip ospf neighbor 
 
OSPF process 100:
Neighbor ID     Pri   State           Dead Time   Address         Interface
ospfd#
 

TROUBLESHOOTING

1) Verify current Hello and Dead intervals advertised by each neighbor on the common interface:

Chassis CBS1

ospfd#show ip ospf interface out
out is up, line protocol is up
  Internet Address 172.16.15.11/24, Area 4.4.1.4, MTU 1500
  Process ID 100, Router ID 192.168.33.50, Network Type BROADCAST, Cost: 110
  Transmit Delay is 1 sec, State DR, Priority 1
  Designated Router (ID) 192.168.33.50, Interface Address 172.16.15.11
  No backup designated router on this network
  Timer intervals configured, Hello 1, Dead 6, Wait 6, Retransmit 5
    Hello due in 00:00:01
  Neighbor Count is 0, Adjacent neighbor count is 0
  Crypt Sequence Number is 1621
  Hello received 0 sent 1189, DD received 0 sent 0
  LS-Req received 0 sent 0, LS-Upd received 0 sent 0
  LS-Ack received 0 sent 0, Discarded 122
  
Chassis CBS2

ospfd#show ip ospf interface out
out is up, line protocol is up
  Internet Address 172.16.15.1/24, Area 4.4.1.4, MTU 1500
  Process ID 100, Router ID 192.168.33.170, Network Type BROADCAST, Cost: 10
  Transmit Delay is 1 sec, State DR, Priority 1
  Designated Router (ID) 192.168.33.170, Interface Address 172.16.15.1
  No backup designated router on this network
  Timer intervals configured, Hello 10, Dead 40, Wait 40, Retransmit 5
    Hello due in 00:00:01
  Neighbor Count is 0, Adjacent neighbor count is 0
  Crypt Sequence Number is 575955
  Hello received 455 sent 1280, DD received 4 sent 3
  LS-Req received 1 sent 1, LS-Upd received 7 sent 17
  LS-Ack received 16 sent 7, Discarded 1172
  

2) Compare OSPF configuration for the common interface:

Chassis CBS1

ospfd# show running
<output removed>
!
interface out
 ip ospf hello-interval 1
 ip ospf dead-interval 6
!
<output removed>

Chassis CBS2
 
ospfd# show running
<output removed>
!
interface out
!
<output removed>
 
Note: Interface on chassis CBS2 has default values for Hello and Dead and therefore they are missing in the show running command.
 

3) If necessary, enable debugging of Hello packets and review the debug log
 

CBS1# routing-protocol ospf vap-group fw configure 

ospfd#configure terminal
ospfd(config)#debug ospf ifsm
ospfd(config)#log file /tmp/ospf_cbs1.txt
ospfd(config)#end

 
CBS1# un su
[[email protected] admin]# rsh fw_1
fw_1 (cbs1): ~# cd /tmp/
fw_1 (cbs1): tmp# cat ospf_cbs1.txt 
<...output removed...>
2012/08/07 11:58:11 OSPF: -----------------------------------------------------
2012/08/07 11:58:11 OSPF: RECV[Hello]: From 192.168.33.170 via out:172.16.15.11 (172.16.15.1 -> 224.0.0.5)
2012/08/07 11:58:11 OSPF: -----------------------------------------------------
2012/08/07 11:58:11 OSPF: Header
2012/08/07 11:58:11 OSPF:   Version 2
2012/08/07 11:58:11 OSPF:   Type 1 (Hello)
2012/08/07 11:58:11 OSPF:   Packet Len 44
2012/08/07 11:58:11 OSPF:   Router ID 192.168.33.170
2012/08/07 11:58:11 OSPF:   Area ID 4.4.1.4
2012/08/07 11:58:11 OSPF:   Checksum 0x5432
2012/08/07 11:58:11 OSPF:   AuType 0
2012/08/07 11:58:11 OSPF: Hello
2012/08/07 11:58:11 OSPF:   NetworkMask 255.255.255.0
2012/08/07 11:58:11 OSPF:   HelloInterval 10
2012/08/07 11:58:11 OSPF:   Options 0x8 (-|-|-|-|N/P|-|-|-)
2012/08/07 11:58:11 OSPF:   RtrPriority 1
2012/08/07 11:58:11 OSPF:   RtrDeadInterval 40
2012/08/07 11:58:11 OSPF:   DRouter 172.16.15.1
2012/08/07 11:58:11 OSPF:   BDRouter 0.0.0.0
2012/08/07 11:58:11 OSPF:   # Neighbors 0
2012/08/07 11:58:11 OSPF: -----------------------------------------------------
2012/08/07 11:58:11 OSPF: RECV[Hello]: From 192.168.33.170 via out:172.16.15.11: HelloInterval mismatch
2012/08/07 11:58:12 OSPF: IFSM[out:172.16.15.11]: Hello timer expire
2012/08/07 11:58:12 OSPF: SEND[Hello]: To 224.0.0.5 via out:172.16.15.11, length 44
2012/08/07 11:58:12 OSPF: -----------------------------------------------------
2012/08/07 11:58:12 OSPF: Header
2012/08/07 11:58:12 OSPF:   Version 2
2012/08/07 11:58:12 OSPF:   Type 1 (Hello)
2012/08/07 11:58:12 OSPF:   Packet Len 44
2012/08/07 11:58:12 OSPF:   Router ID 192.168.33.50
2012/08/07 11:58:12 OSPF:   Area ID 4.4.1.4
2012/08/07 11:58:12 OSPF:   Checksum 0x54cb
2012/08/07 11:58:12 OSPF:   AuType 0
2012/08/07 11:58:12 OSPF: Hello
2012/08/07 11:58:12 OSPF:   NetworkMask 255.255.255.0
2012/08/07 11:58:12 OSPF:   HelloInterval 1
2012/08/07 11:58:12 OSPF:   Options 0x8 (-|-|-|-|N/P|-|-|-)
2012/08/07 11:58:12 OSPF:   RtrPriority 1
2012/08/07 11:58:12 OSPF:   RtrDeadInterval 6
2012/08/07 11:58:12 OSPF:   DRouter 172.16.15.11
2012/08/07 11:58:12 OSPF:   BDRouter 0.0.0.0
2012/08/07 11:58:12 OSPF:   # Neighbors 0
<...output removed...>


All three troubleshooting steps reveal a mismatch in the HelloInterval value between the two neighbors.
   
 

Cause

OSPF routers cannot form neighbor relationship due to a mismatch in Hello or Dead parameters. Following parameters in Hello packets should match between neighboring routers:

  • Hello and Dead intervals

  • Area ID

  • Authentication type and password

  • Stub Area flag

  • Subnet ID and Subnet mask

Resolution

In order to establish OSPF adjacency both OSPF routers must advertise the same Hello and Dead interval values. To correct the above example, parameters on chassis CBS2 can be changed:

Chassis CBS2 

ospfd#configure terminal
ospfd(config)#interface out
ospfd(config-if)#ip ospf hello-interval 1
ospfd(config-if)#ip ospf dead-interval 6
ospfd(config-if)#end
 
ospfd#show ip ospf neighbor
OSPF process 100:
Neighbor ID     Pri   State           Dead Time   Address         Interface
192.168.33.50     1   Full/DR         00:00:06    172.16.15.11    out
 
Chassis CBS1 
 
ospfd#show ip ospf neighbor
 
OSPF process 100:
Neighbor ID     Pri   State           Dead Time   Address         Interface
192.168.33.170    1   Full/Backup     00:00:06    172.16.15.1     out
 

Workaround

N/A

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