OSPF Procces ID

Process IDs need to match within the router or your interfaces will be in separate OSPF instances.

Process id used by ospf is only to differentiate between the different processes if more than one ospf is running on the router. Its like to denote the different database formed by different ospf processes.

Process id can be any number the only thing required is the area and timers should match.

– All routers are running OSPF.
– R3 is running OSPF process 1 on network {R3-left} and OSPF process 10 on network {R3-right}.

Then:
+ R3 will have network {R1-Left} in its RIB via OSPF process 1.
+ R3 will have network {R2-Left} in its RIB because it’s directly connected.
+ R3’s OSPF-10 LSDB will not have any info about networks {R4-Left} or {R5-Left}.
+ R4’s OSPF LSDB is identical to R3’s OSPF-200-LSDB. Thus, neither {R1-Left} nor {R2-Left} will be in its RIB.

R4 LSDB
OSPF Router with ID (3.3.3.2) (Process ID 10)

Router Link States (Area 20)

Link ID ADV Router Age Seq# Checksum Link count
3.3.3.2 3.3.3.2 31 0x80000009 0x0010EA 1
4.4.4.1 4.4.4.1 618 0x8000000B 0x00F2FD 1
192.168.5.1 192.168.5.1 27 0x80000015 0x00B272 1

192.168.5.1 address is in PID: 10.

R3 LSDB
– No 192.168.5.

Solution: Redistribute OSPF Process 10 to OSPF Process 1 on R4

Configuration:
R4(config)#router ospf 1
R4(config-router)#redistribute ospf 10 subnets

Type-5 AS External Link States

Link ID ADV Router Age Seq# Checksum Tag
4.4.4.0 4.4.4.1 556 0x80000002 0x003069 0
172.1.5.1 4.4.4.1 58 0x80000001 0x00BA37 0
192.168.5.1 4.4.4.1 181 0x80000001 0x00D95C 0

Why do we need to use different PID?
Suppose you work for company Alpha, who just acquired company Omega, and both companies run OSPF across their internal networks. Your long-term goal may be to integrate the two network infrastructures, but your short-term goal may be to simply get them talking. This would be one of several interim solutions.

http://costiser.ro/2013/01/10/redistribute-different-ospf-processes/#.WbrTtrIjGUk
http://www.techexams.net/forums/ccna-ccent/76615-ospf-process-id-need-not-match-network-warrior-sorta-implies-otherwise.html