OSPF stub area configuration example
Network requirements
Enable OSPF on all switches, and split the AS into three areas.
Configure Switch A and Switch B as ABRs to forward routing information between areas.
Configure Switch D as the ASBR to redistribute static routes.
Configure Area 1 as a stub area to reduce advertised LSAs without influencing reachability.
Figure 25: Network diagram
Configuration procedure
Configure IP addresses for interfaces. (Details not shown.)
Enable OSPF (see "Basic OSPF configuration example").
Configure route redistribution:
# Configure Switch D to redistribute static routes.
<SwitchD> system-view [SwitchD] ip route-static 3.1.2.1 24 10.5.1.2 [SwitchD] ospf [SwitchD-ospf-1] import-route static [SwitchD-ospf-1] quit
# Display ABR/ASBR information on Switch C.
<SwitchC> display ospf abr-asbr OSPF Process 1 with Router ID 10.4.1.1 Routing Table to ABR and ASBR Type Destination Area Cost Nexthop RtType Intra 10.2.1.1 0.0.0.1 3 10.2.1.1 ABR Inter 10.5.1.1 0.0.0.1 7 10.2.1.1 ASBR# Display OSPF routing table on Switch C.
<SwitchC> display ospf routing OSPF Process 1 with Router ID 10.4.1.1 Routing Tables Routing for Network Destination Cost Type NextHop AdvRouter Area 10.2.1.0/24 3 Transit 10.2.1.2 10.2.1.1 0.0.0.1 10.3.1.0/24 7 Inter 10.2.1.1 10.2.1.1 0.0.0.1 10.4.1.0/24 3 Stub 10.4.1.1 10.4.1.1 0.0.0.1 10.5.1.0/24 17 Inter 10.2.1.1 10.2.1.1 0.0.0.1 10.1.1.0/24 5 Inter 10.2.1.1 10.2.1.1 0.0.0.1 Routing for ASEs Destination Cost Type Tag NextHop AdvRouter 3.1.2.0/24 1 Type2 1 10.2.1.1 10.5.1.1 Total Nets: 6 Intra Area: 2 Inter Area: 3 ASE: 1 NSSA: 0Because Switch C resides in a normal OSPF area, its routing table contains an AS external route.
Configure Area 1 as a stub area:
# Configure Switch A.
<SwitchA> system-view [SwitchA] ospf [SwitchA-ospf-1] area 1 [SwitchA-ospf-1-area-0.0.0.1] stub [SwitchA-ospf-1-area-0.0.0.1] quit [SwitchA-ospf-1] quit
# Configure Switch C.
<SwitchC> system-view [SwitchC] ospf [SwitchC-ospf-1] area 1 [SwitchC-ospf-1-area-0.0.0.1] stub [SwitchC-ospf-1-area-0.0.0.1] quit [SwitchC-ospf-1] quit
# Display OSPF routing information on Switch C
[SwitchC] display ospf routing OSPF Process 1 with Router ID 10.4.1.1 Routing Tables Routing for Network Destination Cost Type NextHop AdvRouter Area 0.0.0.0/0 4 Inter 10.2.1.1 10.2.1.1 0.0.0.1 10.2.1.0/24 3 Transit 10.2.1.2 10.2.1.1 0.0.0.1 10.3.1.0/24 7 Inter 10.2.1.1 10.2.1.1 0.0.0.1 10.4.1.0/24 3 Stub 10.4.1.1 10.4.1.1 0.0.0.1 10.5.1.0/24 17 Inter 10.2.1.1 10.2.1.1 0.0.0.1 10.1.1.0/24 5 Inter 10.2.1.1 10.2.1.1 0.0.0.1 Total Nets: 6 Intra Area: 2 Inter Area: 4 ASE: 0 NSSA: 0After the area where Switch C resides is configured as a stub area, a default route takes the place of the AS external route.
# Configure the area as a totally stub area by filtering Type-3 LSAs out of the stub area.
[SwitchA] ospf [SwitchA-ospf-1] area 1 [SwitchA-ospf-1-area-0.0.0.1] stub no-summary [SwitchA-ospf-1-area-0.0.0.1] quit
# Display OSPF routing information on Switch C.
[SwitchC] display ospf routing OSPF Process 1 with Router ID 10.4.1.1 Routing Tables Routing for Network Destination Cost Type NextHop AdvRouter Area 0.0.0.0/0 4 Inter 10.2.1.1 10.2.1.1 0.0.0.1 10.2.1.0/24 3 Transit 10.2.1.2 10.4.1.1 0.0.0.1 10.4.1.0/24 3 Stub 10.4.1.1 10.4.1.1 0.0.0.1 Total Nets: 3 Intra Area: 2 Inter Area: 1 ASE: 0 NSSA: 0After this configuration, inter-area routes are removed, and only one external route (a default route) exists.