VIRTUAL LINK
Friday, November 14, 2008
starting off with VIRTUAL LINK
VIRTUAL LINK :
THE MAIN RULE IN OSPF IS THAT OTHER AREAS IN OSPF MUST CONNECT DIRECTLY TO BACKBONE AREA THROUGH AN ABR. THE ABR IS RESIDENT IN BOTH AREAS AND HOLDS A TOPOLOGICAL DATABASE FOR EACH AREA .IF DIRECT CONNECTION TO BACKBONE IS NOT POSSIBLE FOR THE NEW AREA .. TWO AREAS ARE SET UP TO BRIDGE THROGH A VIRTUAL LINK.
let us look on r3 ... the entire of 192.168.x.x network is not advertised into ospf .... first we will advertise it and later on create a virtual link..
firstly see the routing table on r3 and r2 to see that network 192.168.x.x is not yet advertised
CODE
r3#sir
Codes: C - connected, S - static, R - RIP, M - mobile, B - BGP
D - EIGRP, EX - EIGRP external, O - OSPF, IA - OSPF inter area
N1 - OSPF NSSA external type 1, N2 - OSPF NSSA external type 2
E1 - OSPF external type 1, E2 - OSPF external type 2
i - IS-IS, su - IS-IS summary, L1 - IS-IS level-1, L2 - IS-IS level-2
ia - IS-IS inter area, * - candidate default, U - per-user static route
o - ODR, P - periodic downloaded static route
Gateway of last resort is 10.1.23.1 to network 0.0.0.0
172.30.0.0/32 is subnetted, 1 subnets
O IA 172.30.30.1 [110/129] via 10.1.23.1, 00:03:44, Serial2/1
10.0.0.0/8 is variably subnetted, 5 subnets, 2 masks
O IA 10.1.12.0/24 [110/128] via 10.1.23.1, 00:03:44, Serial2/1
C 10.1.3.0/24 is directly connected, Loopback3
O 10.1.2.0/24 [110/65] via 10.1.23.1, 00:03:44, Serial2/1
O IA 10.1.1.1/32 [110/129] via 10.1.23.1, 00:03:44, Serial2/1
C 10.1.23.0/24 is directly connected, Serial2/1
C 192.168.102.0/24 is directly connected, Loopback102
C 192.168.103.0/24 is directly connected, Loopback103
C 192.168.100.0/24 is directly connected, Loopback100
C 192.168.101.0/24 is directly connected, Loopback101
O*E2 0.0.0.0/0 [110/1] via 10.1.23.1, 00:03:44, Serial2/1
r3#
as#2
[Resuming connection 2 to r2 ... ]
r2#sir
Codes: C - connected, S - static, R - RIP, M - mobile, B - BGP
D - EIGRP, EX - EIGRP external, O - OSPF, IA - OSPF inter area
N1 - OSPF NSSA external type 1, N2 - OSPF NSSA external type 2
E1 - OSPF external type 1, E2 - OSPF external type 2
i - IS-IS, su - IS-IS summary, L1 - IS-IS level-1, L2 - IS-IS level-2
ia - IS-IS inter area, * - candidate default, U - per-user static route
o - ODR, P - periodic downloaded static route
Gateway of last resort is 10.1.12.1 to network 0.0.0.0
172.30.0.0/32 is subnetted, 1 subnets
O 172.30.30.1 [110/65] via 10.1.12.1, 00:05:17, Serial2/0
10.0.0.0/8 is variably subnetted, 5 subnets, 2 masks
C 10.1.12.0/24 is directly connected, Serial2/0
O 10.1.3.1/32 [110/65] via 10.1.23.2, 00:05:17, Serial2/1
C 10.1.2.0/24 is directly connected, Loopback2
O 10.1.1.1/32 [110/65] via 10.1.12.1, 00:05:17, Serial2/0
C 10.1.23.0/24 is directly connected, Serial2/1
O*E2 0.0.0.0/0 [110/1] via 10.1.12.1, 00:05:17, Serial2/0
r2#
Codes: C - connected, S - static, R - RIP, M - mobile, B - BGP
D - EIGRP, EX - EIGRP external, O - OSPF, IA - OSPF inter area
N1 - OSPF NSSA external type 1, N2 - OSPF NSSA external type 2
E1 - OSPF external type 1, E2 - OSPF external type 2
i - IS-IS, su - IS-IS summary, L1 - IS-IS level-1, L2 - IS-IS level-2
ia - IS-IS inter area, * - candidate default, U - per-user static route
o - ODR, P - periodic downloaded static route
Gateway of last resort is 10.1.23.1 to network 0.0.0.0
172.30.0.0/32 is subnetted, 1 subnets
O IA 172.30.30.1 [110/129] via 10.1.23.1, 00:03:44, Serial2/1
10.0.0.0/8 is variably subnetted, 5 subnets, 2 masks
O IA 10.1.12.0/24 [110/128] via 10.1.23.1, 00:03:44, Serial2/1
C 10.1.3.0/24 is directly connected, Loopback3
O 10.1.2.0/24 [110/65] via 10.1.23.1, 00:03:44, Serial2/1
O IA 10.1.1.1/32 [110/129] via 10.1.23.1, 00:03:44, Serial2/1
C 10.1.23.0/24 is directly connected, Serial2/1
C 192.168.102.0/24 is directly connected, Loopback102
C 192.168.103.0/24 is directly connected, Loopback103
C 192.168.100.0/24 is directly connected, Loopback100
C 192.168.101.0/24 is directly connected, Loopback101
O*E2 0.0.0.0/0 [110/1] via 10.1.23.1, 00:03:44, Serial2/1
r3#
as#2
[Resuming connection 2 to r2 ... ]
r2#sir
Codes: C - connected, S - static, R - RIP, M - mobile, B - BGP
D - EIGRP, EX - EIGRP external, O - OSPF, IA - OSPF inter area
N1 - OSPF NSSA external type 1, N2 - OSPF NSSA external type 2
E1 - OSPF external type 1, E2 - OSPF external type 2
i - IS-IS, su - IS-IS summary, L1 - IS-IS level-1, L2 - IS-IS level-2
ia - IS-IS inter area, * - candidate default, U - per-user static route
o - ODR, P - periodic downloaded static route
Gateway of last resort is 10.1.12.1 to network 0.0.0.0
172.30.0.0/32 is subnetted, 1 subnets
O 172.30.30.1 [110/65] via 10.1.12.1, 00:05:17, Serial2/0
10.0.0.0/8 is variably subnetted, 5 subnets, 2 masks
C 10.1.12.0/24 is directly connected, Serial2/0
O 10.1.3.1/32 [110/65] via 10.1.23.2, 00:05:17, Serial2/1
C 10.1.2.0/24 is directly connected, Loopback2
O 10.1.1.1/32 [110/65] via 10.1.12.1, 00:05:17, Serial2/0
C 10.1.23.0/24 is directly connected, Serial2/1
O*E2 0.0.0.0/0 [110/1] via 10.1.12.1, 00:05:17, Serial2/0
r2#
now on purpose create and advertise all of 192.168.x.x for area 100 in ospf to demonstrate the virtual link
CODE
r3#config t
Enter configuration commands, one per line. End with CNTL/Z.
r3(config)#router ospf 1
r3(config-router)#network 192.168.100.1 0.0.0.0 area 100
r3(config-router)#network 192.168.101.1 0.0.0.0 area 100
r3(config-router)#network 192.168.102.1 0.0.0.0 area 100
r3(config-router)#network 192.168.103.1 0.0.0.0 area 100
r3(config-router)#exit
Enter configuration commands, one per line. End with CNTL/Z.
r3(config)#router ospf 1
r3(config-router)#network 192.168.100.1 0.0.0.0 area 100
r3(config-router)#network 192.168.101.1 0.0.0.0 area 100
r3(config-router)#network 192.168.102.1 0.0.0.0 area 100
r3(config-router)#network 192.168.103.1 0.0.0.0 area 100
r3(config-router)#exit
compare if this is advertised into r2 or r1 ospf proc .. it should not as area 100 is not directly connected to area 0
CODE
r1#sir
Codes: C - connected, S - static, R - RIP, M - mobile, B - BGP
D - EIGRP, EX - EIGRP external, O - OSPF, IA - OSPF inter area
N1 - OSPF NSSA external type 1, N2 - OSPF NSSA external type 2
E1 - OSPF external type 1, E2 - OSPF external type 2
i - IS-IS, su - IS-IS summary, L1 - IS-IS level-1, L2 - IS-IS level-2
ia - IS-IS inter area, * - candidate default, U - per-user static route
o - ODR, P - periodic downloaded static route
Gateway of last resort is not set
172.30.0.0/30 is subnetted, 1 subnets
C 172.30.30.0 is directly connected, Loopback30
10.0.0.0/8 is variably subnetted, 5 subnets, 2 masks
C 10.1.12.0/24 is directly connected, Serial2/0
O IA 10.1.3.1/32 [110/129] via 10.1.12.2, 00:10:22, Serial2/0
O IA 10.1.2.0/24 [110/65] via 10.1.12.2, 00:10:22, Serial2/0
C 10.1.1.0/24 is directly connected, Loopback1
O IA 10.1.23.0/24 [110/128] via 10.1.12.2, 00:10:22, Serial2/0
r1#
as#2
[Resuming connection 2 to r2 ... ]
r2#sir
Codes: C - connected, S - static, R - RIP, M - mobile, B - BGP
D - EIGRP, EX - EIGRP external, O - OSPF, IA - OSPF inter area
N1 - OSPF NSSA external type 1, N2 - OSPF NSSA external type 2
E1 - OSPF external type 1, E2 - OSPF external type 2
i - IS-IS, su - IS-IS summary, L1 - IS-IS level-1, L2 - IS-IS level-2
ia - IS-IS inter area, * - candidate default, U - per-user static route
o - ODR, P - periodic downloaded static route
Gateway of last resort is 10.1.12.1 to network 0.0.0.0
172.30.0.0/32 is subnetted, 1 subnets
O 172.30.30.1 [110/65] via 10.1.12.1, 00:09:17, Serial2/0
10.0.0.0/8 is variably subnetted, 5 subnets, 2 masks
C 10.1.12.0/24 is directly connected, Serial2/0
O 10.1.3.1/32 [110/65] via 10.1.23.2, 00:09:17, Serial2/1
C 10.1.2.0/24 is directly connected, Loopback2
O 10.1.1.1/32 [110/65] via 10.1.12.1, 00:09:17, Serial2/0
C 10.1.23.0/24 is directly connected, Serial2/1
O*E2 0.0.0.0/0 [110/1] via 10.1.12.1, 00:09:17, Serial2/0
r2#
Codes: C - connected, S - static, R - RIP, M - mobile, B - BGP
D - EIGRP, EX - EIGRP external, O - OSPF, IA - OSPF inter area
N1 - OSPF NSSA external type 1, N2 - OSPF NSSA external type 2
E1 - OSPF external type 1, E2 - OSPF external type 2
i - IS-IS, su - IS-IS summary, L1 - IS-IS level-1, L2 - IS-IS level-2
ia - IS-IS inter area, * - candidate default, U - per-user static route
o - ODR, P - periodic downloaded static route
Gateway of last resort is not set
172.30.0.0/30 is subnetted, 1 subnets
C 172.30.30.0 is directly connected, Loopback30
10.0.0.0/8 is variably subnetted, 5 subnets, 2 masks
C 10.1.12.0/24 is directly connected, Serial2/0
O IA 10.1.3.1/32 [110/129] via 10.1.12.2, 00:10:22, Serial2/0
O IA 10.1.2.0/24 [110/65] via 10.1.12.2, 00:10:22, Serial2/0
C 10.1.1.0/24 is directly connected, Loopback1
O IA 10.1.23.0/24 [110/128] via 10.1.12.2, 00:10:22, Serial2/0
r1#
as#2
[Resuming connection 2 to r2 ... ]
r2#sir
Codes: C - connected, S - static, R - RIP, M - mobile, B - BGP
D - EIGRP, EX - EIGRP external, O - OSPF, IA - OSPF inter area
N1 - OSPF NSSA external type 1, N2 - OSPF NSSA external type 2
E1 - OSPF external type 1, E2 - OSPF external type 2
i - IS-IS, su - IS-IS summary, L1 - IS-IS level-1, L2 - IS-IS level-2
ia - IS-IS inter area, * - candidate default, U - per-user static route
o - ODR, P - periodic downloaded static route
Gateway of last resort is 10.1.12.1 to network 0.0.0.0
172.30.0.0/32 is subnetted, 1 subnets
O 172.30.30.1 [110/65] via 10.1.12.1, 00:09:17, Serial2/0
10.0.0.0/8 is variably subnetted, 5 subnets, 2 masks
C 10.1.12.0/24 is directly connected, Serial2/0
O 10.1.3.1/32 [110/65] via 10.1.23.2, 00:09:17, Serial2/1
C 10.1.2.0/24 is directly connected, Loopback2
O 10.1.1.1/32 [110/65] via 10.1.12.1, 00:09:17, Serial2/0
C 10.1.23.0/24 is directly connected, Serial2/1
O*E2 0.0.0.0/0 [110/1] via 10.1.12.1, 00:09:17, Serial2/0
r2#
now create the virtual link
*** IAM A DUMB HERE AND FORGOT WHAT TO DO WHILE CONFIGURING VIRTUAL LINK. YES I WAS CONFUSED WHETHER TO GIVE AREA NUMBER IN COMMAND 0 WHICH RELATES TO NEW AREA OR ABR AREA .... BE CAREFUL ITS ALWAYS THE ABR AREA CONNECTED TO AREA 0 SHOULD BE GIVEN WHICH IS 23 DONT COMMIT THIS MISTAKE PLEASE... IF YOU DO SO NO HARM .. BECAUSE YOU CANNOT SEE IN THE OTHER ROUTING TABLE SO YOU NEED TO GIVE ANOTHER AREA NUMBER OBVIOUSLY .. BUT IS THAT THE CONCEPT OR WHAT WE UNDERSTOOD????
VIRTUAL LINK MUST AND SHOULD BE CONFIGURED ON BOTH OF THE ROUTERS ...DID YOU SEE NOW ROUTER 3 IS ALSO AN ABR ....? SO IT WOULD BE SAFE TO SAY THAT .. VIRTUAL LINKS SHOULD BE CONFIGURED BETWEEN ORIGINAL ABR AND WOULD BE ABR
