Virtual Link Configuration
Syntax
router ospf 1
area [transit-area] virtual-link [remote-router-id]
Configure on BOTH routers
Configuration Example
Topology
R1 (Area 0) --- R2 (Area 0 + Area 10) --- R3 (Area 0)
Transit: Area 10
R2 Configuration
router ospf 1
router-id 2.2.2.2
area 10 virtual-link 3.3.3.3
R3 Configuration
router ospf 1
router-id 3.3.3.3
area 10 virtual-link 2.2.2.2
Result: Virtual link through Area 10 connects R2 and R3
Verification
R2# show ip ospf virtual-links
Virtual Link OSPF_VL0 to router 3.3.3.3 is up
Transit area 10
Transmit Delay is 1 sec, State POINT_TO_POINT,
Timer intervals configured, Hello 10, Dead 40
Why Virtual Links Are Temporary
❌ Not a permanent solution
❌ Adds complexity
❌ Hard to troubleshoot
❌ Performance overhead
Use only until you can redesign the network properly
Summary
✅ Virtual links fix discontiguous Area 0
✅ Configure on both routers through transit area
✅ Temporary solution only
✅ Redesign network as soon as possible
Next: Learn about OSPF Timers (Article 16)
Internal Links:
- ← OSPF Stub Areas (Article 14)
- → OSPF Timers (Article 16)
- → Design Best Practices (Article 30)
