Re: [Xen-users] Strange Networking Issue

[jez <jez@xxxxxxxxxx>]

On Sat, Mar 10, 2007 at 04:33:03PM -0500, Jonathon Jones wrote:
> jez wrote:
> >
> >It sounds like at the moment they are treating each of your 8 addresses
> >as host addresses (probably in a /22 block). Question: If you add each
> >of theses 8 addresses to eth1 on Dom0 like:
> >
> >    ip addr add xxx.xxx.154.240/22 dev eth1
> >
> >can you ping each address?
> >
> >If you can, then you should be able to use a bridging setup on Dom0 and
> >keep all 8 addresses.
> >
> >  
> No, using the command you gave me does not allow the IP addresses to 
> work.  However, adding them individually does like:
>        ip addr add xxx.xxx.154.247 dev eth1

I meant you to add them individually. I think you might be confusing
what the /22 means. It doesn't mean "add this block of addresses" - it
means "add this address with a netmask of 255.255.252.0". If you do an
"ip addr show" at the moment you will see that each of your new
addresses have a /32 mask which means 255.255.255.255. 

Anyway, it's  good news for you that all your addresses are presently
considered host addresses. Before trying anything else, remove all those
addresses we just added to eth1 - execpt the .178 one of course.

What I recommend that you try is to configure eth1 on Dom0 with a /22
netmask instead of the /29 that it has now. It should appear as
x.x.153.178/22 to "ip addr show". Why? well, at the moment eth1 isn't on
the same subnet as x.x.x.240 - 248. If eth1 wanted to send a message to
one of those addresses it would send it to the router at x.x.153.177. 
Whereas, if you change it's mask then it will try to contact those 
addresses directly.

After that, configure each of the DomUs with all their addresses having 
a /22 mask also. Keep using the same default gateway (x.x.153.177) for all 
machines. 

If things aren't working, sniff the lines with tcpdump to get an idea 
of what's happening.

Let us know how you get on.


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