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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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