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Re: [Xen-users] Yet another question about multiple NICs



I am a bit confused now. What did I explained so badly ? Do I understand you well ? I said I ran ip neigh from both machines, as requested. And from dom1 the output is similar to the output I dumped, but only when the connection succeeds. Because, once again, dom1 and dom0 are never "connected" at the same time, that is the issue. When dom0 (resp. dom1) fails to connect to the network, then 'ip neigh' shows nothing.

Regards,
Philippe

Felix Kuperjans wrote:
I meant to do ip neigh within dom1 - you wrote your output was from dom0.
Is the dom0 able to reach machines on the networks?

Regards,
Felix

Am 20.12.2010 04:12, schrieb Philippe Combes:

Felix Kuperjans wrote :
Answers within quotes:
- It's interesting that dom1's firewall output shows that no packages
were processed, so maybe you didn't ping anything since the last
reboot
from dom1 or the firewall was loaded by reading it's statistics...
You requested for the outputs "when <my> system has just started".
Hence no packet, I guess. But shouldn't there be at least those
exchanged
for the ssh connection to the dom1 ?
Anyway, after one minute or so, I get on the dom1:
# iptables -nvL
Chain INPUT (policy ACCEPT 23 packets, 884 bytes)
 pkts bytes target     prot opt in     out     source
destination

Chain FORWARD (policy ACCEPT 0 packets, 0 bytes)
 pkts bytes target     prot opt in     out     source
destination

Chain OUTPUT (policy ACCEPT 4 packets, 816 bytes)
 pkts bytes target     prot opt in     out     source
destination
That looks better.
Still no reasons why you can't ping local machines from the dom1 (and
sometimes even not from dom0). Have you tried pinging each other, so
dom0 -> dom1 and vice versa?
Yes I tried, and it has always worked while dom0's eth1 was up.
So it's only impossible to ping the domU from other machines on the
network (and vice versa)?
I think Fajar is probably right with his guess that your physical
switches are managed. That means they do traffic filtering on their
ports based on the mac addresses.
Which switch models do you use on your two networks?
I already answered Fajar in this thread: when the FIRST vif of dom1 is
connected to dom0's eth1, then the behaviour on that switched LAN is
normal, while the traffic on the routed LAN of dom0's eth0 issues the
bug.
So my issue is definetely related to the instanciation of the SECOND
interface of dom1, whatever network it is connected to. Or there is
some kind of black magic underneath...


The only remaining thing that denies communication would be ARP, so
the
output of:
# ip neigh show
on both machines *directly after* a ping would be nice (within a few
seconds - use && and a time-terminated ping).
Nothing on a machine when not connected. But when connected (here the
dom0):
$ ip neigh show
192.168.24.125 dev eth1 lladdr 00:16:36:e0:81:2c REACHABLE
172.16.113.100 dev eth0 lladdr 00:16:38:4c:04:00 DELAY
172.16.113.123 dev eth0 lladdr 00:16:36:e0:81:2e STALE
172.16.113.124 dev eth0 lladdr 00:1b:24:3d:ca:95 REACHABLE
172.16.113.106 dev eth0 lladdr 00:16:38:28:b5:39 REACHABLE
ARP seems to work at least on the Domain-0 *if* one of those IP
addresses is the one of the domU...
Can you try doing this on the DomU when pinging a host in the network?
I did ! As requested ! And as you know, dom0 and dom1 are
alternatively connected. When dom0 is connected (172.16.113.121 on
eth0 and 192.168.24.123 on eth1) I get the trace above, but nothing
from dom1. When dom1 is connected, I get a similar trace from dom1,
but nothing from dom0 (I mean nothing on network 192.168.24.0)

Regards,
Philippe

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