OSPF Packets and Neighbor Discovery

Objective:

1. To determine what’s constitute the OSPF Packets.
2. To understand the 7 State process on how OSPF neighbors were formed.

OSPF Configurations of MANILA & MELBOURNE Router:

MANILA#sh run | sec ospf
router ospf 1
network 100.100.100.0 0.0.0.255 area 0
network 192.168.12.0 0.0.0.255 area 0
MANILA#

MELBOURNE#sh run | sec ospf
router ospf 1
network 192.168.12.0 0.0.0.255 area 0
network 200.200.200.0 0.0.0.255 area 0
MELBOURNE#

Let’s enabled “debug ip ospf packet” on MANILA Router:

MANILA#debug ip ospf packet
OSPF packet debugging is on
MANILA#
*Jul 19 22:53:33.791: OSPF-1 PAK : rcv. v:2 t:1 l:48 rid:200.200.200.1 aid:0.0.0.0 chk:936A aut:0 auk: from Serial2/0
MANILA#

Illustration the above concepts on the how OSPF neighbors were formed, let’s enabled “debug ip ospf adj”on the MANILA Router and observed what happens:

MANILA#debug ip ospf adj
OSPF adjacency debugging is on

To restart the OSPF process, let’ execute “clear ip ospf process” in the user mode in MANILA Router and go through the console logs and identify the various States before OSPF neighbors were formed:

MANILA#clear ip ospf process
Reset ALL OSPF processes? [no]: yes

FIRST STATE: DOWN

MANILA#
*Jul 19 23:28:32.355: OSPF-1 ADJ   Lo1: Interface going Down
*Jul 19 23:28:32.355: OSPF-1 ADJ   Lo1: 100.100.100.1 address 100.100.100.1 is dead, state DOWN
*Jul 19 23:28:32.359: OSPF-1 ADJ   Se2/0: Interface going Down
*Jul 19 23:28:32.359: OSPF-1 ADJ   Se2/0: 200.200.200.1 address 192.168.12.2 is dead, state DOWN
*Jul 19 23:28:32.359: %OSPF-5-ADJCHG: Process 1, Nbr 200.200.200.1 on Serial2/0 from FULL to DOWN, Neighbor Down: Interface down or detached
MANILA#
*Jul 19 23:28:32.363: OSPF-1 ADJ   Se2/0: Nbr 200.200.200.1: Clean-up dbase exchange
*Jul 19 23:28:32.367: OSPF-1 ADJ   Se2/0: 100.100.100.1 address 192.168.12.1 is dead, state DOWN

SECOND STATE: INIT

*Jul 19 23:28:32.371: OSPF-1 ADJ Lo1: Interface going Up
*Jul 19 23:28:32.375: OSPF-1 ADJ Se2/0: Interface going Up

I will illustrate further the INIT State by enabled “debug ip ospf hello”on MANILA Router and clear again the OSPF Process.

MANILA#debug ip ospf hello
OSPF hello debugging is on

MANILA#clear ip ospf process
Reset ALL OSPF processes? [no]: yes
*Jul 19 23:51:15.459: OSPF-1 HELLO Se2/0: Rcv hello from 200.200.200.1 area 0 192.168.12.2
yes
MANILA#
*Jul 19 23:51:17.623: %OSPF-5-ADJCHG: Process 1, Nbr 200.200.200.1 on Serial2/0 from FULL to DOWN, Neighbor Down: Interface down or detached
*Jul 19 23:51:17.631: OSPF-1 HELLO Se2/0: Send hello to 224.0.0.5 area 0 from 192.168.12.1
*Jul 19 23:51:17.651: OSPF-1 HELLO Se2/0: Rcv hello from 200.200.200.1 area 0 192.168.12.2
*Jul 19 23:51:17.655: OSPF-1 HELLO Se2/0: Send immediate hello to nbr 200.200.200.1, src address 192.168.12.2
*Jul 19 23:51:17.655: OSPF-1 HELLO Se2/0: Send hello to 224.0.0.5 area 0 from 192.168.12.1MANILA#
*Jul 19 23:51:17.835: %OSPF-5-ADJCHG: Process 1, Nbr 200.200.200.1 on Serial2/0 from LOADING to FULL, Loading Done

THIRD STATE: TWO-WAY

*Jul 19 23:28:32.395: OSPF-1 ADJ Se2/0: 2 Way Communication to 200.200.200.1, state 2WAY

FOURTH STATE: EXSTART

*Jul 19 23:28:32.399: OSPF-1 ADJ Se2/0: Nbr 200.200.200.1: Prepare dbase exchange

*Jul 19 23:28:32.399: OSPF-1 ADJ Se2/0: Send DBD to 200.200.200.1 seq 0x1691 opt 0x52 flag 0x7 len 32
*Jul 19 23:28:32.487: OSPF-1 ADJ Se2/0: Rcv DBD from 200.200.200.1 seq 0x15C opt 0x52 flag 0x7 len 32 mtu 1500 state EXSTART

*Jul 19 23:28:32.487: OSPF-1 ADJ Se2/0: NBR Negotiation Done. We are the SLAVE

FIFTH STATE: EXCHANGE

*Jul 19 23:28:32.491: OSPF-1 ADJ   Se2/0: Nbr 200.200.200.1: Summary list built, size 0
*Jul 19 23:28:32.491: OSPF-1 ADJ   Se2/0: Send DBD to 200.200.200.1 seq 0x15C opt 0x52 flag 0x0 len 32
*Jul
MANILA#19 23:28:32.555: OSPF-1 ADJ   Se2/0: Rcv DBD from 200.200.200.1 seq 0x15D opt 0x52 flag 0x1 len 52 mtu 1500 state EXCHANGE
*Jul 19 23:28:32.555: OSPF-1 ADJ   Se2/0: Exchange Done with 200.200.200.1

SIX STATE: LOADING

*Jul 19 23:28:32.559: OSPF-1 ADJ   Se2/0: Send LS REQ to 200.200.200.1 length 36 LSA count 1
*Jul 19 23:28:32.559: OSPF-1 ADJ   Se2/0: Send DBD to 200.200.200.1 seq 0x15D opt 0x52 flag 0x0 len 32
*Jul 19 23:28:32.623: OSPF-1 ADJ   Se2/0: Rcv LS UPD from 200.200.200.1 length 88 LSA count 1

SEVEN STATE: FULL

*Jul 19 23:28:32.623: OSPF-1 ADJ Se2/0: Synchronized with 200.200.200.1, state FULL
*Jul 19 23:28:32.627: %OSPF-5-ADJCHG: Process 1, Nbr 200.200.200.1 on Serial2/0 from LOADING to FULL, Loading Done

NETWORK LESSON