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tech:network:cisco:ospf:virtual-link:virtual-link

Cisco: OSPF Virtual Link

Topology

Base Configuration

Common Configuration Snippet

R1

R2

R3

R4

R5

Tasks

  1. cehck network status before virtual-link configuration
  2. Starndard Area: allowed
  3. NSSA: not allowed
  4. Totally NSSA: not allowed
  5. Stub Area, Totally Stub Area: not allowed

Configuring Virtual Link: Standard Area 19cc0813-1412-46bc-8299-0115f6c9daaf

  • R2
configure terminal
!
router ospf 1
 area 10 virtual-link 4.4.4.4
exit
!
end
  • R4
configure terminal
!
router ospf 1
 area 10 virtual-link 2.2.2.2
exit
!
end

Verification

DNA means DO NOT AGE?

  • Wireshark Display Filter
ospf

R1 Console Log

R2 Console Log

R3 Console Log

R4 Console Log

R5 Console Log

Virtual Link Packet is may be unicast packet. Destination address is not multicast.

Configuring Virtual Link: NSSA 71958c79-97ff-4b0f-9077-372dad07a1d3

  • R2
configure terminal
!
router ospf 1
 area 10 nssa
 area 10 virtual-link 4.4.4.4
exit
!
end
  • R3
configure terminal
!
router ospf 1
 area 10 nssa
exit
!
end
  • R4
configure terminal
!
router ospf 1
 area 10 nssa
 area 10 virtual-link 2.2.2.2
exit
!
end

Verification

R2 Console Log

R3 Console Log

R4 Console Log

Configuring Virtual Link: Totally NSSA 1f27f794-2a25-46d0-866c-c2e2b64d1ea2

  • R2
configure terminal
!
router ospf 1
 area 10 nssa
 area 10 virtual-link 4.4.4.4
exit
!
end
  • R3
configure terminal
!
router ospf 1
 area 10 nssa
exit
!
end
  • R4
configure terminal
!
router ospf 1
 area 10 nssa no-summary
 area 10 virtual-link 2.2.2.2
exit
!
end

Verification

see above verification.

Key Point

  1. Packet Capture Only, It's hard to understand OSPF Virtual Link…
  2. OSPF Virtual Link Packet destination is unicast address, not multicast address…(may be)?
  3. Virtual Link will be up when opposite side node Virtual Link configured?

Verification Commands Sumamry

show ip ospf virtual-links
show ip ospf neighbor
show running-config | section router ospf 1
show ip route ospf
show ip ospf database
  • Wireshark Display Filter
ospf

References

tech/network/cisco/ospf/virtual-link/virtual-link.txt · Last modified: 2020/02/29 16:17 by wnoguchi