Aprile 2004 Ultimo aggiornamento - Aggiornamenti successivi vai a libro routing -
Esempi sulla propagazione della route di default in RIP-IGRP-EIGRP
Nell'esempio a seguire due router, "itesys1" e "itesys2"
sono collegati tra loro tramite WAN. Il router "itesys2" ha accesso ad
internet tramite un gateway in LAN, con IP 192.168.0.2. L'esempio mostra come
propagano questa route di default RIP, IGRP e EIGRP
Ecco il router "itesys2" con una corretta e funzionante configurazione con RIP:
... snip ...
!
interface FastEthernet0/0
ip address 192.168.0.2 255.255.255.0
no ip directed-broadcast
duplex auto
speed auto
!
interface Serial0/0
ip address 128.10.10.2 255.255.255.252
no ip directed-broadcast
no ip mroute-cache
no fair-queue
!
interface FastEthernet0/1
no ip address
no ip directed-broadcast
shutdown
duplex auto
speed auto
!
router rip
network 128.10.0.0
network 192.168.0.0
default-information originate
!
ip classless
ip route 0.0.0.0 0.0.0.0 192.168.0.1
Sovrapponiamo al RIP di "itesys2" una configurazione IGRP:
itesys2#conf t
itesys2(config)#router igrp 10
itesys2(config-router)#network 128.10.10.0
itesys2(config-router)#network 192.168.190.0
Vediamo cosa succede al router adiacente (che ha sia RIP che IGRP):
itesys1#sh ip route
Codes: C - connected, S - static, I - IGRP, 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, E - EGP
i - IS-IS, 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 128.10.10.2 to network 0.0.0.0
C 192.168.94.0/24 is directly connected, FastEthernet0/0
128.10.0.0/30 is subnetted, 1 subnets
C 128.10.10.0 is directly connected, Serial0/0
I 192.168.0.0/24 [100/8486] via 128.10.10.2, 00:00:00, Serial0/0
R* 0.0.0.0/0 [120/1] via 128.10.10.2, 00:00:25, Serial0/0
IGRP non propaga la route di default cosi' non la sovrascrive. Le altre route
RIP sono sovrascritte a causa della minore AD di IRGP.
Adesso togliamo il RIP. Ad 'itesys2' facciamo propagare tramite IGRP la route di
default. "default-information originate" non funziona cosi' come non
funziona "redistribute static" o "ip default-gateway". E'
necessario l'uso di "ip default-network":
itesys2#conf t
Enter configuration commands, one per line. End with CNTL/Z.
itesys2(config)#ip default-network ?
A.B.C.D IP address of default network
itesys2(config)#ip default-network 192.168.0.0
itesys2(config)#exit
itesys2#sh run
Building configuration...
...snip...
!
router igrp 10
network 128.10.0.0
network 192.168.0.0
!
ip classless
ip default-network 192.168.0.0
ip route 0.0.0.0 0.0.0.0 192.168.0.1
ip route 192.168.0.0 255.255.255.0 192.168.0.1
...snip...
itesys2#sh ip route
Codes: C - connected, S - static, I - IGRP, 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, E - EGP
i - IS-IS, 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 192.168.0.1 to network 0.0.0.0
I 192.168.94.0/24 [100/8486] via 128.10.10.1, 00:00:05, Serial0/0
128.10.0.0/30 is subnetted, 1 subnets
C 128.10.10.0 is directly connected, Serial0/0
C* 192.168.0.0/24 is directly connected, FastEthernet0/0
S* 0.0.0.0/0 [1/0] via 192.168.0.1
Notate come la Fast0/0 abbia adesso C* nella tabella di routing. Questa informazione sara' propagata da IGRP:
itesys1#sh ip route
Codes: C - connected, S - static, I - IGRP, 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, E - EGP
i - IS-IS, 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 128.10.10.2 to network 192.168.0.0
C 192.168.94.0/24 is directly connected, FastEthernet0/0
128.10.0.0/16 is variably subnetted, 2 subnets, 2 masks
C 128.10.10.0/30 is directly connected, Serial0/0
D 128.10.0.0/16 is a summary, 00:01:42, Null0
D* 192.168.0.0/24 [90/2172416] via 128.10.10.2, 00:01:16, Serial0/0
Adesso aggiungiamo EIGRP ad 'itesys2' e togliamo "ip default-network":
...snip...
!
router eigrp 15
network 128.10.0.0
network 192.168.0.0
!
router igrp 10
network 128.10.0.0
network 192.168.0.0
!
ip classless
ip route 0.0.0.0 0.0.0.0 192.168.0.1
ip route 192.168.0.0 255.255.255.0 192.168.0.1
no ip http server
itesys1#sh ip route
Codes: C - connected, S - static, I - IGRP, 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, E - EGP
i - IS-IS, 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 128.10.10.2 to network 192.168.0.0
C 192.168.94.0/24 is directly connected, FastEthernet0/0
128.10.0.0/16 is variably subnetted, 2 subnets, 2 masks
C 128.10.10.0/30 is directly connected, Serial0/0
D 128.10.0.0/16 is a summary, 00:02:23, Null0
D 192.168.0.0/24 [90/2172416] via 128.10.10.2, 00:00:25, Serial0/0
itesys1#exit
togliamo "ip default-network" e, per propagare la route di default con EIGRP usiamo "redistribute static":
itesys2(config)#router eigrp 15
itesys2(config-router)#redistribute static
itesys2(config-router)#exit
itesys2(config)#exit
itesys1#sh ip route
Codes: C - connected, S - static, I - IGRP, 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, E - EGP
i - IS-IS, 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 128.10.10.2 to network 0.0.0.0
C 192.168.94.0/24 is directly connected, FastEthernet0/0
128.10.0.0/16 is variably subnetted, 2 subnets, 2 masks
C 128.10.10.0/30 is directly connected, Serial0/0
D 128.10.0.0/16 is a summary, 00:02:57, Null0
D 192.168.0.0/24 [90/2172416] via 128.10.10.2, 00:00:59, Serial0/0
D*EX 0.0.0.0/0 [170/2172416] via 128.10.10.2, 00:00:14, Serial0/0
itesys1#
Per EIGRP avremmo potuto utilizzare anche "ip default-network"