sull’ospf

r-sopra#sh run
Building configuration...
..
..
interface Ethernet0/0
ip address 192.168.106.4 255.255.255.192
full-duplex
!
interface Serial1/0
ip address 172.21.4.2 255.255.255.252
no fair-queue
..
..
router ospf 1
router-id 10.106.110.4
log-adjacency-changes
network 172.21.4.0 0.0.0.3 area 1
network 192.168.106.0 0.0.0.63 area 0

r-sotto#sh run
Building configuration...
..
..
interface Serial1/0
ip address 172.21.4.1 255.255.255.252
clock rate 115200
!
..
..
!
router ospf 1
router-id 172.21.4.1
log-adjacency-changes
network 172.21.4.0 0.0.0.3 area 1
!


in questo modo, r-sotto si becca la rotta 192.168.106.0/26 (inter-area):

r-sotto#sh ip route
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

192.168.106.0/26 is subnetted, 1 subnets
O IA 192.168.106.0 [110/791] via 172.21.4.2, 00:08:54, Serial1/0
172.21.0.0/30 is subnetted, 1 subnets
C 172.21.4.0 is directly connected, Serial1/0

se configuro l’area 1 stub, viene generata automaticamente la rotta di default:

r-sopra(config)#router ospf 1
r-sopra(config-router)#area 1 stu
r-sopra(config-router)#area 1 stub
r-sopra(config-router)#

r-sotto(config)#router ospf 1
r-sotto(config-router)#area 1 stu
r-sotto(config-router)#area 1 stub
r-sotto(config-router)#^Z
r-sotto#

r-sotto#sh ip route
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

192.168.106.0/26 is subnetted, 1 subnets
O IA 192.168.106.0 [110/791] via 172.21.4.2, 00:00:00, Serial1/0
172.21.0.0/30 is subnetted, 1 subnets
C 172.21.4.0 is directly connected, Serial1/0
O*IA 0.0.0.0/0 [110/782] via 172.21.4.2, 00:00:00, Serial1/0

se invece configuro l’area come NSSA, la rotta di default non viene automaticamente injectata:

r-sopra(config-router)#no area 1 stub
r-sopra(config-router)#ara 1
*Mar 1 00:53:07.873: %OSPF-5-ADJCHG: Process 1, Nbr 172.21.4.1 on Serial1/0 from FULL to DOWN, Neighbor Down: Adjacency forced to
r-sopra(config-router)#
r-sopra(config-router)#area 1 ns
r-sopra(config-router)#area 1 nssa
r-sopra(config-router)#

r-sotto(config-router)#no area 1 stub
r-sotto(config-router)#area 1 nssa
r-sotto(config-router)#

192.168.106.0/26 is subnetted, 1 subnets
O IA 192.168.106.0 [110/791] via 172.21.4.2, 00:00:13, Serial1/0
172.21.0.0/30 is subnetted, 1 subnets
C 172.21.4.0 is directly connected, Serial1/0
r-sotto#


due scelte: o si fa (sempre sull’ABR) area 1 nssa no-summary:

r-sopra(config-router)#area 1 nssa no-summary
r-sopra(config-router)#

e viene generata una rotta di default inter-area:

r-sotto#
*Mar 1 00:54:01.661: %SYS-5-CONFIG_I: Configured from console by console
r-sotto#sh ip route
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

Link ID ADV Router Age Seq# Checksum
0.0.0.0 10.106.110.4 48 0x80000001 0x006EE0

oppure si fa area 1 nssa default-information-originate, e si genera una LSA di tipo 7, rotta esterna:

r-sotto#sh ip route
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

Link ID ADV Router Age Seq# Checksum Tag
0.0.0.0 10.106.110.4 35 0x80000001 0x00FA08 0