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tech:network:cisco:ospf:area-prefix-list:area-prefix-list

Cisco: OSPF: Inter-Area Route Filtering

My Learning topics result may not be accurate because of my misunderstanding!!!!

I STRONGLY RECOMMENDED to read the Official Documents(cisco.com a.k.a. CCO) and RFCs, any other books, sites.

And learn foundation, create lab yourself, configure, and verify any topics.

Base Lab 1: OSPF Route Filtering Lab 581c807c-e998-4929-9f53-7685fc6c3b88

Topology

Base Configuration

Common Configuration Snippet

R1

R2

R3

Configuring Inter Area Route Filtering 4fa45a7b-4cb0-4848-9f20-c059e56ee8d3

  • R2
configure terminal
!
ip prefix-list PRE-AREA10-OUT deny 1.1.2.0/24
ip prefix-list PRE-AREA10-OUT deny 1.1.4.0/24
ip prefix-list PRE-AREA10-OUT permit 0.0.0.0/0 le 32
!
ip prefix-list PRE-AREA10-IN deny 3.3.5.3/24
ip prefix-list PRE-AREA10-IN deny
!
router ospf 1
 area 10 filter-list prefix PRE-AREA10-OUT out
 area 10 filter-list prefix PRE-AREA10-IN in
!
end
  • le: less than or equal to
  • ge: greater than equal to

Verification

show ip interface brief
show ip route ospf
show ip ospf database
show ip prefix-list detail <word>

R1 Console Log

R2 Console Log

R3 Console Log

R2#sh ip prefix-list detail 
Prefix-list with the last deletion/insertion: PRE-AREA10-OUT
ip prefix-list PRE-AREA10-IN:
   count: 2, range entries: 1, sequences: 5 - 10, refcount: 2
   seq 5 deny 3.3.5.0/24 (hit count: 1, refcount: 1)
   seq 10 permit 0.0.0.0/0 le 32 (hit count: 9, refcount: 1)
ip prefix-list PRE-AREA10-OUT:
   count: 3, range entries: 1, sequences: 5 - 15, refcount: 3
   seq 5 deny 1.1.2.0/24 (hit count: 1, refcount: 1)
   seq 10 deny 1.1.4.0/24 (hit count: 1, refcount: 2)
   seq 15 permit 0.0.0.0/0 le 32 (hit count: 7, refcount: 1)

hit count can check ABR OSPF database.

R2#sh ip ospf database | begin Summary Net Link States \(Area 0\) 
                Summary Net Link States (Area 0)

Link ID         ADV Router      Age         Seq#       Checksum
1.1.0.0         2.2.2.2         544         0x80000001 0x0048E8
1.1.1.0         2.2.2.2         544         0x80000001 0x003DF2
1.1.3.0         2.2.2.2         544         0x80000001 0x002707
1.1.5.0         2.2.2.2         544         0x80000001 0x00111B
1.1.6.0         2.2.2.2         544         0x80000001 0x000625
10.1.1.0        2.2.2.2         544         0x80000001 0x00C75F
10.1.2.0        2.2.2.2         584         0x80000001 0x00B274
R2#sh ip ospf database | begin Summary Net Link States \(Area 10\)
                Summary Net Link States (Area 10)

Link ID         ADV Router      Age         Seq#       Checksum
2.2.2.2         2.2.2.2         548         0x80000001 0x00FA31
3.3.0.0         2.2.2.2         498         0x80000001 0x001617
3.3.1.0         2.2.2.2         498         0x80000001 0x000B21
3.3.2.0         2.2.2.2         498         0x80000001 0x00FF2B
3.3.3.0         2.2.2.2         498         0x80000001 0x00F435
3.3.4.0         2.2.2.2         498         0x80000001 0x00E93F
3.3.6.0         2.2.2.2         498         0x80000001 0x00D353
10.2.3.0        2.2.2.2         548         0x80000001 0x009B89
10.3.3.0        2.2.2.2         498         0x80000001 0x009989

References

tech/network/cisco/ospf/area-prefix-list/area-prefix-list.txt · Last modified: 2020/04/17 19:49 by wnoguchi