Xen users - Jun 2005 - Connect vif to vif with a bridge. MAC failure.

I nearly went cracy about this.

Here the failure:

Two domUs:

First domU MacAddress in config file other than aa:00:00:00:00:xx.
Second aa:00:00:00:00:11

One bridge with no ethx connected but with the ip 192.168.1.1.

Second can ping 192.168.1.1
First not.

I tried everything. Changing the distros configs itself. Changing the 
hostname. Some variations in the order i added the doms to the bridge, I 
really dont know what to do anymore.

So the last thing i tried was to set the mac from the first dom to one of the 
form aa:00:00:00:00:xx. And it works. Now even the first dom can ping the 
second. Nice.

But why?

Greetings Dominik

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> First domU MacAddress in config file other than aa:00:00:00:00:xx.
> Second aa:00:00:00:00:11
> 
> One bridge with no ethx connected but with the ip 192.168.1.1.
> 
> Second can ping 192.168.1.1
> First not.
> 
> I tried everything. Changing the distros configs itself. 
> Changing the hostname. Some variations in the order i added 
> the doms to the bridge, I really dont know what to do anymore.
> 
> So the last thing i tried was to set the mac from the first 
> dom to one of the form aa:00:00:00:00:xx. And it works. Now 
> even the first dom can ping the second. Nice.
> 
> But why?
Mac adresses staring with the first two or three bits set are something
special (broadcast,multicast ... )

Please let you mac Address start with 00: or at least 0x: and try again.

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> Mac adresses staring with the first two or three bits set are something
> special (broadcast,multicast ... )
More specifically - the low order bit of the first (high order) octet...
> Please let you mac Address start with 00: or at least 0x: and try again.
... so 0x: is only safe if x is in {0, 2, 4, 6, 8, A, C, E}.

A generally safe format is yx:yy:yy:yy:yy:yy where y is any digit (0-F) 
and x is in {2, 6, A, E} (these are "locally assigned" address rather 
than "universal" addresses allocated to hardware vendors).

James


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