[Xorp-users] ARP problems with static routes in XORP
allan at vyatta.com
Wed Jun 7 08:35:03 PDT 2006
It looks like your host may be doing the right thing, depending on how you have your default gateway set up. The host is sending an ARP for the destination IP address and the router (220.127.116.11) should reply with a proxy ARP if it has a route to 10.1.1.2. I'm assuming that this router has a directly connected route to 10.1.1.0/24.
I would make sure that:
1) the host has a default gateway set to 18.104.22.168. You can use netstat -r (Linux/Win) and check for the presence of a 0.0.0.0/0 route to 22.214.171.124.
2) the router has a connected route to 10.1.1.0/24 (my assumption on your subnet mask)
3) the router at 10.1.1.2 has a route (static or RIP derived) back to 126.96.36.199/24 (again, I'm assuming you're using a /24 here again).
----- Original Message -----
From: Vikram KAUL <vkaul at research.telcordia.com>
To: xorp-users at xorp.org
Sent: Wednesday, June 7, 2006 8:17:39 AM GMT-0800
Subject: [Xorp-users] ARP problems with static routes in XORP
I need help with a skeletal XORP setup with 3 routers and two hosts. I am
seeing the problem with static routes as well as with RIP, so I will just
describe the static case, and hope I can resolve the problem
The network is laid out like follows
17.17.17.x 10.1.1.x 192.168.0.x 16.16.16.x
H ---------- R ---------- R ------------- R ----------- H
.20 .1 .1 .2 .2 .3 .3 .20
HostA : 188.8.131.52
Router1: 184.108.40.206 & 10.1.1.1
Router2: 10.1.1.2 & 192.168.0.2
Router3: 192.168.0.3 & 220.127.116.11
HostB : 18.104.22.168
When I configure XORP for static routes (or even RIP), the unicast tables
appear properly in the routers (1,2,3). I am able to ping and traceroute
from one to the other without any problems
Then, when I connect the host (HostA) and configure the default gw to be
22.214.171.124 it does the following:
Ping from 126.96.36.199 (host) to 188.8.131.52 (gw router) is OK
Ping from 184.108.40.206 (host) to 10.1.1.1 (gw router, next interface) is OK
Ping from 220.127.116.11 (host) to 10.1.1.2 (next hop after gw) FAILS
Same is the case in the opposite direction
I ran tcpdump on the 18.104.22.168 interface on Router1 and it is getting arp
arp who-is 10.1.1.2 tell 22.214.171.124
Why is this happening ?
Shouldn't the host merely send the ping packet to the gw router which
should then forward it to the next hop and get the reply back in the same
Why is arp for 10.1.1.2 being sent out by the host (126.96.36.199) ?
Is this a configuration issue at the host ? or something in XORP ?
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