OSPF Virtual Link Configuration Guide
Configure Virtual Links
The single backbone area (area 0.0.0.0), cannot be disconnected, or certain areas of the Autonomous System will become unreachable. To establish and maintain connectivity of the backbone, virtual links can be configured through non-backbone areas. Virtual links serve to connect physically separate components of the backbone.
The two endpoints of a virtual link are Area Border Routers (ARBs). The virtual link must be configured in both routers. The configuration information in each router consists of the other virtual endpoint (the other ARB), and the non-backbone area that the two routers have in common (called the transit area). Virtual links cannot be configured through stub areas.
Enable OSPF on Switch A, B, C, and D at the beginning. There is no route entry from the backbone area (0.0.0.0) to area 2.2.2.2.
Figure 5-7. Virtual link configuration.
Configuring Switch A
admin@XorPlus# set vlans vlan-id 500 l3-interface vlan-500 admin@XorPlus# set vlan-interface interface vlan-500 vif vlan-500 address 192.168.1.2 prefix-length 30 admin@XorPlus# set interface gigabit-ethernet ge-1/1/47 family ethernet-switching native-vlan-id 500 admin@XorPlus# set protocols ospf4 router-id 1.1.1.1 admin@XorPlus# set protocols ospf4 area 0.0.0.0 interface vlan-500 vif vlan-500 address 192.168.1.2 admin@XorPlus#commit Waiting for merging configuration. Commit OK. Save Done. admin@XorPlus#
Configuring Switch B
admin@XorPlus# set vlans vlan-id 400 l3-interface vlan-400 admin@XorPlus# set vlan-interface interface vlan-400 vif vlan-400 address 172.25.150.250 prefix-length 30 admin@XorPlus# set vlans vlan-id 500 l3-interface vlan-500 admin@XorPlus# set vlan-interface interface vlan-500 vif vlan-500 address 192.168.1.1 prefix-length 30 admin@XorPlus# set interface gigabit-ethernet ge-1/1/48 family ethernet-switching native-vlan-id 500 admin@XorPlus# set interface gigabit-ethernet ge-1/1/2 family ethernet-switching native-vlan-id 400 admin@XorPlus# set protocols ospf4 router-id 4.4.4.4 admin@XorPlus# set protocols ospf4 area 0.0.0.0 interface vlan-500 vif vlan-500 address 192.168.1.1 admin@XorPlus# set protocols ospf4 area 1.1.1.1 interface vlan-400 vif vlan-400 address 172.25.150.250 admin@XorPlus#commit Waiting for merging configuration. Commit OK. Save Done. admin@XorPlus#
Configuring Switch C
admin@XorPlus# set vlans vlan-id 300 l3-interface vlan-300 admin@XorPlus# set vlan-interface interface vlan-300 vif vlan-300 address 172.25.150.246 prefix-length 30 admin@XorPlus# set vlans vlan-id 400 l3-interface vlan-400 admin@XorPlus# set vlan-interface interface vlan-400 vif vlan-400 address 172.25.150.249 prefix-length 30 admin@XorPlus# set interface gigabit-ethernet te-1/1/49 family ethernet-switching native-vlan-id 300 admin@XorPlus# set interface gigabit-ethernet te-1/1/51 family ethernet-switching native-vlan-id 400 admin@XorPlus# set protocols ospf4 router-id 3.3.3.3 admin@XorPlus# set protocols ospf4 area 2.2.2.2 interface vlan-300 vif vlan-300 address 172.25.150.246 admin@XorPlus# set protocols ospf4 area 1.1.1.1 interface vlan-400 vif vlan-400 address 172.25.150.249 admin@XorPlus#commit Waiting for merging configuration. Commit OK. Save Done. admin@XorPlus#
Configuring Switch D
admin@XorPlus# set vlans vlan-id 300 l3-interface vlan-300 admin@XorPlus# set vlan-interface interface vlan-300 vif vlan-300 address 172.25.150.245 prefix-length 30 admin@XorPlus# set interface gigabit-ethernet te-1/1/49 family ethernet-switching native-vlan-id 300 admin@XorPlus# set protocols ospf4 router-id 2.2.2.2 admin@XorPlus# set protocols ospf4 area 2.2.2.2 interface vlan-300 vif vlan-300 address 172.25.150.245 admin@XorPlus#commit Waiting for merging configuration. Commit OK. Save Done. admin@XorPlus#
Enable Virtual Links on the Area Border Routers
(Switch B and Switch C). After this step, there will be a route entry from the backbone area, 0.0.0.0 to area 2.2.2.2
Configuring Switch B
admin@XorPlus# set protocols ospf4 area 0.0.0.0 virtual-link 3.3.3.3 transmit-area 1.1.1.1 admin@XorPlus#commit Waiting for merging configuration. Commit OK. Save Done. admin@XorPlus#
Configuring Switch C
admin@XorPlus# set protocols ospf4 area 0.0.0.0 virtual-link 4.4.4.4 transmit-area 1.1.1.1 admin@XorPlus#commit Waiting for merging configuration. Commit OK. Save Done. admin@XorPlus#
Checking an IPv4 OSPF
Check ipv4 ospf neighbor on Switch B.
admin@Xorplus# run show ospf4 neighbor Address Interface State Router ID Pri Dead --------------- --------------------- -------- --------------- ----- ---- 172.25.150.249 vlan-400/vlan-400 Full 3.3.3.3 128 39 192.168.1.2 vlan-500/vlan-500 Full 1.1.1.1 128 39 172.25.150.249 vlink/3.3.3.3 Full 3.3.3.3 128 39
Configuring Switch B
admin@XorPlus# set vlans vlan-id 500 l3-interface vlan-500 admin@XorPlus# set vlan-interface interface vlan-500 vif vlan-500 address 192.168.1.1 prefix-length 30 admin@XorPlus# set interface gigabit-ethernet ge-1/1/48 family ethernet-switching native-vlan-id 500 admin@XorPlus# set protocols ospf4 router-id 4.4.4.4 admin@XorPlus# set protocols ospf4 area 0.0.0.0 interface vlan-100 vif vlan-500 address 192.168.1.1 admin@XorPlus# set vlans vlan-id 400 l3-interface vlan-400 admin@XorPlus# set vlan-interface interface vlan-400 vif vlan-400 address 172.25.150.250 prefix-length 30 admin@XorPlus# set interface gigabit-ethernet ge-1/1/2 family ethernet-switching native-vlan-id 400 admin@XorPlus# set protocols ospf4 area 0.0.0.0 interface vlan-400 vif vlan-400 address 172.25.150.250 admin@XorPlus#commit Waiting for merging configuration. Commit OK. Save Done. admin@XorPlus#
Configuring Switch C
admin@XorPlus# set vlans vlan-id 400 l3-interface vlan-400 admin@XorPlus# set vlan-interface interface vlan-400 vif vlan-400 address 172.25.150.249 prefix-length 30 admin@XorPlus# set interface gigabit-ethernet te-1/1/49 family ethernet-switching native-vlan-id 400 admin@XorPlus# set protocols ospf4 router-id 3.3.3.3 admin@XorPlus# set protocols ospf4 area 0.0.0.0 interface vlan-400 vif vlan-400 address 172.25.150.249 admin@XorPlus#commit Waiting for merging configuration. Commit OK. Save Done. admin@XorPlus#
Configuring Area 1.1.1.1 as a Stub area or NSSA
admin@XorPlus# set protocols ospf4 area 1.1.1.1 area-type <normal | stub | nssa> admin@XorPlus# commit Waiting for merging configuration. Commit OK. Save done. admin@XorPlus#
Check route table on DUT3,there will be route entry to backbone area 192.168.1.0/30
admin@XorPlus# run show route forward-route ipv4 all Destination NetMask NextHopMac Port --------------- ----------------- --------- 172.25.150.248 255.255.255.252 08:9E:01:62:D5:61 connected 192.168.1.0 255.255.255. 252 60:EB:69:9B:BE:31 te-1/1/51 Total route count:2
Disabling the summary function on ABR(DUT2 area 1.1.1.1)
admin@XorPlus# set protocols ospf4 area 1.1.1.1 summaries disable true admin@XorPlus# commit Waiting for merging configuration. Commit OK. Save done. admin@XorPlus#
Check route table on DUT3, the route entry to backbone area was lost
admin@XorPlus# run show route forward-route ipv4 all Destination NetMask NextHopMac Port --------------- ----------------- --------- 172.25.150.248 255.255.255.252 08:9E:01:62:D5:61 connected Total route count:1
Enable default-lsa function on ABR(DUT2)
admin@XorPlus# run show route forward-route ipv4 all Destination NetMask NextHopMac Port --------------- ----------------- --------- 172.25.150.248 255.255.255.252 08:9E:01:62:D5:61 connected 0.0.0.0 0.0.0.0 60:EB:69:9B:BE:31 te-1/1/51 Total route count:2
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