Default-Network Command

[KShardha]

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I am facing difficulty while applying default-network command. I have three routers in my topology(in a row!!!). The router in middle (A) is supposed to run default-network command and RIP with router on right(B). The router on left (ISP) has static route to router A(0.0.0.0 0.0.0.0), the router on right(B) runs RIP. Here is the configuration for ISP and router A:

ISP(config)#do sh run
Building configuration...

Current configuration : 597 bytes
!
version 12.2
no service password-encryption
!
hostname ISP
!
!
!
!
!
ip ssh version 1
!
!
interface FastEthernet0/0
ip address 172.16.20.1 255.255.255.0
duplex auto
speed auto
!
interface FastEthernet1/0
no ip address
duplex auto
speed auto
shutdown
!
interface Serial2/0
ip address 172.16.10.1 255.255.255.252
clock rate 4000000
!
interface Serial3/0
no ip address
shutdown
!
interface FastEthernet4/0
no ip address
shutdown
!
interface FastEthernet5/0
no ip address
shutdown
!
ip classless
ip route 0.0.0.0 0.0.0.0 172.16.10.2
!
!
!
!
!
line con 0
line vty 0 4
login
!
!
end

A(config)#do sh run
Building configuration...

Current configuration : 667 bytes
!
version 12.2
no service password-encryption
!
hostname A
!
!
!
!
!
ip ssh version 1
!
!
interface FastEthernet0/0
no ip address
duplex auto
speed auto
shutdown
!
interface FastEthernet1/0
no ip address
duplex auto
speed auto
shutdown
!
interface Serial2/0
ip address 172.16.10.2 255.255.255.252
!
interface Serial3/0
ip address 192.168.10.1 255.255.255.0
clock rate 4000000
!
interface FastEthernet4/0
no ip address
shutdown
!
interface FastEthernet5/0
no ip address
shutdown
!
router rip
passive-interface Serial2/0
network 192.168.10.0
!
ip classless
ip route 172.16.0.0 255.255.0.0 172.16.10.0
!
!
!
!
!
line con 0
line vty 0 4
login
!
!
end




The problem is that I can not ping from a pc attached to B to pc attached to ISP. Kindly resolve this issue.

[sukarabi]

First of all I would configure RIPv2 instead of RIPv1 and use the no auto-summary command.

Otherwise the default-network command might not be appropriate here as ISP router doesn't use any routing protocol. It would be better to use the ip route 0.0.0.0 0.0.0.0 serial2/0 or ip route 0.0.0.0 0.0.0.0 172.16.10.1 from RouterA.

The default-route command would be more useful if ISP router was running RIP too and you would like to create a default-route on RouterA to reach a network behind ISP router. In this case you relies on the fact that ISP router advertise the network you want to reach to RouterA (so the default-network command should not be used toward an ISP router as it doesn't run any routing protocol).

Can you send the routing table of each router to check if my answer is ok ?
Thanks

[KShardha]

Thanks. Your suggestions worked out. I was using RIPv1, then i used RIPv2 and it worked.

-cheers!!