Let’s follow up with the second area type which is totally stubby area.
Totally stubby area stops inter-area (LSA 3) and external routes (LSA 5).
Since type 5 external LSAs are blocked, we can’t have an ASBR in a totally stubby area.
Change OSPF area 100 to a totally stubby area.
Configuration and verification:
Configuration is pretty straight forward as we only need to change the configuration on R10.
R10(config)#router ospf 10 R10(config-router)#area 100 stub no-summary
R10 is still neighbor with R11.
R10#sh ip ospf neigh Neighbor ID Pri State Dead Time Address Interface 22.214.171.124 0 FULL/ - 00:00:31 10.10.101.2 Ethernet0/2
Let’s see what’s happening with R11 routing table.
R11# sh ip route ospf Gateway of last resort is 10.10.101.1 to network 0.0.0.0 O*IA 0.0.0.0/0 [110/11] via 10.10.101.1, 00:03:17, Ethernet0/0
R11 is now showing only a default route to R10.
R11 OSPF database is also reduce to a minimum size.
R11#sh ip ospf database OSPF Router with ID (126.96.36.199) (Process ID 10) Router Link States (Area 10) Link ID ADV Router Age Seq# Checksum Link count 188.8.131.52 184.108.40.206 1154 0x80000001 0x00C7FE 2 Router Link States (Area 100) Link ID ADV Router Age Seq# Checksum Link count 100.100.100.100 100.100.100.100 1111 0x80000003 0x00DD60 2 220.127.116.11 18.104.22.168 1145 0x80000002 0x002CE6 2 Summary Net Link States (Area 100) Link ID ADV Router Age Seq# Checksum 0.0.0.0 100.100.100.100 224 0x80000003 0x00E9C0
We can verify that area 100 is configure as totally stubby by checking R10.
R10#sh ip ospf | b Area 100 Area 100 Number of interfaces in this area is 1 It is a stub area, no summary LSA in this area Generates stub default route with cost 1 Area has no authentication SPF algorithm last executed 00:08:40.853 ago SPF algorithm executed 5 times Area ranges are Number of LSA 3. Checksum Sum 0x01F406 Number of opaque link LSA 0. Checksum Sum 0x000000 Number of DCbitless LSA 0 Number of indication LSA 0 Number of DoNotAge LSA 0 Flood list length 0
When using totally stub area, we optimize further the OSPF database.
In the next post, we will finish to explore the area types.
Thank you for reading.
OSPF – Implement and troubleshoot area types – Totally stubby area