Re: [Xen-users] Interdomain routing problem

["Nick Couchman" <Nick.Couchman@xxxxxxxxx>]

Okay, let me make sure I understand your setup here:
 
xmclient1(eth0) - 10.0.1.1
xmrouter1(eth0) - 10.0.1.254
 
xmrouter1(eth1) - 10.0.2.1
xmrouter2(eth0) - 10.0.2.254
 
xmrouter2(eth1) - 10.0.3.1
xmrouter3(eth0) - 10.0.3.254
 
xmrouter3(eth1) - 10.0.4.1
xmserver(eth0) - 10.0.4.254
 
Your routing tables should look something like this
 
xmclient:
10.0.1.0 dev eth0
default router 10.0.1.254
 
xmrouter1
10.0.1.0 dev eth0
10.0.2.0 dev eth1
10.0.3.0 gw 10.0.2.254
10.0.4.0 gw 10.0.2.254
(could also set default gw 10.0.2.254 instead of two previous route entries)
 
xmrouter2
10.0.2.0 dev eth0
10.0.3.0 dev eth1
10.0.1.0 gw 10.0.2.1
10.0.4.0 gw 10.0.3.254
 
xmrouter3
10.0.3.0 dev eth0
10.0.4.0 dev eth1
10.0.1.0 gw 10.0.3.1
10.0.2.0 gw 10.0.3.1
(could also set default gw 10.0.3.1 instead of two prevous route entries)
 
xmserver1
10.0.4.0 dev eth0
default gw 10.0.4.1
 
This should get the traffic from xmclient1 to xmserver1 and back again.  Also make sure you enable ipv4 packet forwarding either via sysctl or manually echoing into the correct /proc location.

Nick Couchman
Systems Integrator
SEAKR Engineering, Inc.
6221 South Racine Circle
Centennial, CO 80111
Main: (303) 790-8499
Fax: (303) 790-8720
Web: http://www.seakr.com

>>> Robert Hulme < rob@xxxxxxxxxxxx > 2005/09/08 16:33 >>>
Could someone please help? I'm trying to setup a 'simulation network'
where there are two domains A and B with 3 'routers' between them.

I have tried the following:
xmclient:~# ifconfig eth0 10.0.1.1 
xmclient:~# route add -net 10.0.4.0 netmask 255.255.255.0 dev eth0

xmrouter1:~# ifconfig eth0 10.0.1.254
xmrouter1:~# ifconfig eth1 10.0.2.1
xmrouter1:~# route add -net 10.0.4.0 netmask 255.255.255.0 dev eth1

xmrouter2:~# ifconfig eth0 10.0.2.254
xmrouter2:~# route add -net 10.0.1.0 netmask 255.255.255.0 dev eth0
xmrouter2:~# ifconfig eth1 10.0.3.1
xmrouter2:~# route add -net 10.0.4.0 netmask 255.255.255.0 dev eth1

xmrouter3:~# ifconfig eth0 10.0.3.254
xmrouter3:~# route add -net 10.0.1.0 netmask 255.255.255.0 dev eth0
xmrouter3:~# ifconfig eth1 10.0.4.1

xmserver:~# ifconfig eth0 10.0.4.254
xmserver:~# route add -net 10.0.1.0 netmask 255.255.255.0 dev eth0


Where in A is xmclient and B is xmserver. What I expect to happen is
now that xmclient and xmserver can talk to one another, and that
packets will merrily hop from xmclient -> xmrouter1 -> xmrouter2 ->
xmrouter3 -> xmserver and backwards...

When I ping I get...

xmserver:~# ping 10.0.1.1
PING 10.0.1.1 (10.0.1.1) 56(84) bytes of data.
64 bytes from 10.0.1.1: icmp_seq=1 ttl=64 time=0.579 ms
64 bytes from 10.0.1.1: icmp_seq=2 ttl=64 time=0.184 ms
64 bytes from 10.0.1.1: icmp_seq=3 ttl=64 time=0.153 ms
64 bytes from 10.0.1.1: icmp_seq=4 ttl=64 time=0.169 ms 

--- 10.0.1.1 ping statistics ---
4 packets transmitted, 4 received, 0% packet loss, time 2999ms
rtt min/avg/max/mdev = 0.153/0.271/0.579/0.178 ms 

All good and hunkey dorey so far :-P

Now to check on the hopping...

xmserver:~# traceroute 10.0.1.1
traceroute to 10.0.1.1 (10.0.1.1), 30 hops max, 38 byte packets
1 10.0.1.1 (10.0.1.1) 0.215 ms 5.151 ms 0.180 ms 

Ah... only one hop, not what I expected...

What have I done wrong? Is it a general networking mistake I've made
in my thinking here or is there some kind of xen magic happening where
xen knows it can route from xmserver to xmclient and so doesn't do all
the intermediate hops I have tried to put in place? If so how can I
prevent that?

Muchos gracias!
-Rob

-- 
------------------------------------------------------
Fran: Do you know that in Tibet when they want something they give
something away?
Bernard: Do they? That must be why they're such a dominant global power. 
-- Black Books

 http://www.robhulme.com/  
 http://robhu.livejournal.com/  

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