[nsp] Static Routing

[Todd, Douglas M.]

 Howdy:

Just wondering: there are no default routes any where, right?  
One thing that is that proxyarp is enabled by default on cisco routers in
some ios releases.  I am not sure when it became disabled by default. 

Do a sh ip int on the out going int on R2 and see if proxyarp is enable. If
is then do
a no ip proxyarp on the interface.  See if the icmp works again.

==DMT>

Douglas Todd
Senior Network Engineer
Partners Health Care
NETENG East



-----Original Message-----
From: odusseus
To: cisco-nsp
Sent: 10/23/02 4:31 AM
Subject: [nsp] Static Routing

Hi again,

I am sorry to insiste but this trouble is still torturing me.
Any opinion or suggestion could release me.


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
------------------------------------------

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