STUB  

Friday, November 14, 2008

DEFINITION OF STUB AREA : A STUB AREA ABR ONLY INJECTS INTER AREA LSA'S AND A DEFAULT ROUTE INTO THE AREA SPECIFIED

so our configuration after implementing stub area should see only these two ...

important point * stub area should be configured on both the routers ..other wise there would be no adj esthablished .. along with the timers it is also important that two of the routers should also agree upon the stub flag ..

area 23 is gng to be made stub

as you can see adj is lost and regained

CODE
r3(config)#router ospf 1
r3(config-router)#area 23 stub
r3(config-router)#
*Mar 1 01:15:18.331: %OSPF-4-ASBR_WITHOUT_VALID_AREA: Router is currently an ASBR while having only one area which is a stub area
r3(config-router)#
as#2
[Resuming connection 2 to r2 ... ]

r2#config t
Enter configuration commands, one per line. End with CNTL/Z.
r2(config)#router ospf 1
r2(config-router)#area 23 stub
r2(config-router)#
*Mar 1 01:15:29.783: %OSPF-5-ADJCHG: Process 1, Nbr 172.20.200.1 on Serial2/1 from FULL to DOWN, Neighbor Down: Adjacency forced to reset
r2(config-router)#



these are the routing tables .. compare with first one to see the diff

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

172.20.0.0/24 is subnetted, 1 subnets
C 172.20.200.0 is directly connected, Loopback20
10.0.0.0/24 is subnetted, 5 subnets
O IA 10.1.12.0 [110/128] via 10.1.23.1, 00:00:29, Serial2/1
C 10.1.3.0 is directly connected, Loopback3
O 10.1.2.0 [110/65] via 10.1.23.1, 00:00:29, Serial2/1
O IA 10.1.1.0 [110/129] via 10.1.23.1, 00:00:29, Serial2/1
C 10.1.23.0 is directly connected, Serial2/1
O*IA 0.0.0.0/0 [110/65] via 10.1.23.1, 00:00:29, Serial2/1
r3#
*Mar 1 01:16:15.303: %SYS-5-CONFIG_I: Configured from console by console
r3#siod

OSPF Router with ID (172.20.200.1) (Process ID 1)

Router Link States (Area 23)

Link ID ADV Router Age Seq# Checksum Link count
10.1.2.1 10.1.2.1 39 0x8000000A 0x00662C 3
172.20.200.1 172.20.200.1 38 0x8000000B 0x008F84 3

Summary Net Link States (Area 23)

Link ID ADV Router Age Seq# Checksum
0.0.0.0 10.1.2.1 48 0x80000001 0x003BF4
10.1.1.0 10.1.2.1 48 0x80000002 0x0022C0
10.1.12.0 10.1.2.1 48 0x80000002 0x009E3A
r3#


here is what indicates the stub area configs on abr

CODE
r2#sio
Routing Process "ospf 1" with ID 10.1.2.1
Start time: 00:13:30.596, Time elapsed: 01:03:34.104
Supports only single TOS(TOS0) routes
Supports opaque LSA
Supports Link-local Signaling (LLS)
Supports area transit capability
It is an area border router
Router is not originating router-LSAs with maximum metric
Initial SPF schedule delay 5000 msecs
Minimum hold time between two consecutive SPFs 10000 msecs
Maximum wait time between two consecutive SPFs 10000 msecs
Incremental-SPF disabled
Minimum LSA interval 5 secs
Minimum LSA arrival 1000 msecs
LSA group pacing timer 240 secs
Interface flood pacing timer 33 msecs
Retransmission pacing timer 66 msecs
Number of external LSA 0. Checksum Sum 0x000000
Number of opaque AS LSA 0. Checksum Sum 0x000000
Number of DCbitless external and opaque AS LSA 0
Number of DoNotAge external and opaque AS LSA 0
Number of areas in this router is 2. 1 normal 1 stub 0 nssa
Number of areas transit capable is 0
External flood list length 0
Area BACKBONE(0)
Number of interfaces in this area is 1
Area has no authentication
SPF algorithm last executed 00:01:35.664 ago
SPF algorithm executed 11 times
Area ranges are
Number of LSA 5. Checksum Sum 0x028ED4
Number of opaque link LSA 0. Checksum Sum 0x000000
Number of DCbitless LSA 0
Number of indication LSA 0
Number of DoNotAge LSA 0
Flood list length 0
Area 23
Number of interfaces in this area is 2
It is a stub area------------------------------------>******************
generates stub default route with cost 1
Area has no authentication
SPF algorithm last executed 00:01:20.668 ago
SPF algorithm executed 17 times
Area ranges are
Number of LSA 5. Checksum Sum 0x028E1C
Number of opaque link LSA 0. Checksum Sum 0x000000
Number of DCbitless LSA 0
Number of indication LSA 0
Number of DoNotAge LSA 0
Flood list length 0

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