[nsp] Routing

[odusseus]

Hi,

I have 3 Cisco routers (2x1601 & 1x1720) running IOS IP PLUS 12.1(17).
These 3 routers are connected to a Cisco switch Cat 2950. (IOS 12.1(6)).
They are all the the same VLAN 1.

R1<-------->R2<---------->R3

Eth0_R1=10.100.100.1/24
Lo0_R1 = 10.10.10.1/32
Lo1_R1 =10.10.10.3/32

Eth0_prim_R2=10.100.100.2/24
Eth0_sec_R2=192.168.100.2/24
Lo0_R2=10.10.10.2/32

Fa0_R3=192.168.100.1/24
Lo0_R3=192.168.200.1/32

This is the log from R2 where R3 is pinging 10.10.10.3 with success:
************
19:50:21: IP: s=192.168.100.1 (Ethernet0), d=10.10.10.3 (Ethernet0), g=10.100.100.1, len 100, forward
19:50:21:     ICMP type=8, code=0

19:50:21: IP: s=10.10.10.3 (Ethernet0), d=192.168.100.1 (Ethernet0), g=192.168.100.1, len 100, forward
19:50:21:     ICMP type=0, code=0
************

Now on R2 I set up a new loopback interface (Lo 1) with this specific IP addresse 10.10.10.3/32 (the same as Lo1_R1).
And I *shut down* this new interface Lo 1.

This is now the log from R2, where R3 is trying to ping 10.10.10.3 (lo0_R1_UP && lo1_R2_DOWN): it failed.
************
19:54:14: IP: s=192.168.100.1 (Ethernet0), d=10.10.10.3 (Ethernet0), g=10.100.100.1, len 100, forward
19:54:14:     ICMP type=8, code=0

19:54:14: IP: s=10.10.10.3 (Ethernet0), d=192.168.100.1 (Ethernet0), len 100, rcvd local pkt
19:54:14:     ICMP type=0, code=0
************

In this second case I don't understand why R2 is forwarding the ICMP 8/0 packet (s=192.168.100.1; d=10.10.10.3) to R1 and does not forward the ICMP 0/0 (s=10.10.10.3; d=192.168.100.1) to R3.

Why R2 is forwarding the ECHO whereas it is considering the ECHO REPLY as a local destination?

Christophe
------------------------------------------

Faites un voeu et puis Voila ! www.voila.fr