OSPF Stub and NSSA Areas with no-summary

By default, external routes and inter-area routes will be injected into stub or NSSAs areas in the same OSPF domain in the absence of effective route summarization. This can overwhelm a node particularly in large OSPF routing domains. Changing an area from stub to a totally-stubby area solves this issue. To change an area from stub to a totally-stubby-area, user can apply the command set protocols ospf area 0.0.0.1 no-summary from the PiCOS configuration mode.

In Figure 5-5 below, Router 2 is an ABR, to reduce the number of routes on Router 1 in area 0.0.0.2, we will configure area 0.0.0.2 on Router 2 as a totally stubby area.

Figure 5-5. OSPF Stub area/NSSA summary: area 1.1.1.1 should be a stub area or an NSSA

Configuring Router 2

admin@router2# set vlans vlan-id 30 l3-interface "vlan30"
admin@router2# set vlans vlan-id 40 l3-interface "vlan40"
admin@router2# set interface gigabit-ethernet ge-1/1/3 family ethernet-switching native-vlan-id 30
admin@router2# set interface gigabit-ethernet ge-1/1/5 family ethernet-switching native-vlan-id 40
admin@router2# set l3-interface vlan-interface vlan30 address 10.10.2.2 prefix-length 24
admin@router2# set l3-interface vlan-interface vlan40 address 10.10.4.1 prefix-length 24
admin@router2# set protocols ospf router-id 2.2.2.2
admin@router2# set protocols ospf area 0.0.0.2 area-type "stub"
admin@router2# set protocols ospf area 0.0.0.2 no-summary
admin@router2# set protocols ospf network 10.10.2.0/24 area 0.0.0.2
admin@router2# set protocols ospf network 10.10.4.0/24 area 0.0.0.0
admin@router2# set l3-interface loopback lo address 2.2.2.2 32 prefix-length 32
Commit OK.
Save Done.
admin@router2#

Similarly, on Router4, we will run the same command to stop injecting summaries in NSSA area 0.0.0.1.

Configuring Router 4

admin@router4# set vlans vlan-id 40 l3-interface "vlan40"
admin@router4# set vlans vlan-id 50 l3-interface "vlan50"
admin@router4# set interface gigabit-ethernet te-1/1/1 family ethernet-switching native-vlan-id 40
admin@router4# set interface gigabit-ethernet te-1/1/2 family ethernet-switching native-vlan-id 50
admin@router4# set l3-interface vlan-interface vlan40 address 10.10.4.2 prefix-length 24
admin@router4# set l3-interface vlan-interface vlan50 address 10.10.5.1 prefix-length 24
admin@router4# set protocols ospf router-id 4.4.4.4
admin@router4# set protocols ospf network 10.10.4.0/24 area 0.0.0.0
admin@router4# set protocols ospf network 10.10.5.0/24 area 0.0.0.1
admin@router4# set protocols ospf area 0.0.0.1 area-type nssa
admin@router4# set protocols ospf area 0.0.0.1 no-summary
admin@router4# set protocols ospf network 4.4.4.4/32 area 0
admin@router4# set protocols ospf redistribute static
admin@router4# set l3-interface loopback lo address 4.4.4.4 prefix-length 32
Commit OK.
Save done.