Re: [Xen-users] Dom0 seeing traffic on br0 but it's not routing

[Alexandre Kouznetsov <alk@xxxxxxxxxx>]

El 22/11/13 14:05, Glenn E. Bailey III escribió:
> Iptables is off, and I've tried dropping the e1000 w/no luck.
"off", you mean, "iptables -L -v" displays no rules and the default 
policy is ACCEPT, right?
iptables can't be "off" as is, it's just a tool to control netfilter, 
which is part of the kernel. It is normally on and permissive by 
default. By kernel's default, not necessarily by the OS default.
> You might be on to something w/the switch idea. So are you saying
> clone Dom0's MAC to DomU's and then see if I can ping the gateway from
> DomU (You stated Dom0)?
Actually, quite opposite. I meant to state Dom0.

I'm assuming that the only difference the switch (and rest of your 
network) can see between traffic from Dom0 and DomU is the MAC address. 
So, since Dom0 is the one who has a known working configuration, let's 
see is the change we want to prove or discard as relevant, breaks things 
there.
I would take DomU's MAC address, shut down DomU, assign that MAC to Dom0 
and see if the rest of your network still want to play with it. If this 
break network for Dom0, you will have to talk to your network 
administrator. If the new MAC works fine, then you'll have to keep 
troubleshooting.
I guess it's possible to do this from the other end, borrowing dom0's 
MAC and giving it to DomU, but this will force you to get a new MAC for 
Dom0 anyway, since they can't share the same physical address. You also 
can't leave Dom0 without MAC at all. More steps, more complex, more 
things to keep in mind. Proof of concept tests shall be simple.
My own past experience I have referenced, had to do with VLAN 
misconfiguration in one case. In other case it was unusually long arp 
cache (around 4 hours) on a L3 switch (or a more robust router, maybe? 
it was out of my scope). That one took me days to troubleshoot and blame 
the network administrator.
BTW, you might consider to set up a fixed MAC address for your DomU.
http://wiki.xen.org/wiki/Xen_Networking#MAC_addresses

Greetings.

--
Alexandre Kouznetsov


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