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RE: [Xen-users] DomU Bridged vs. Routed Networking?

To: "Nivedita Singhvi" <nsnix@xxxxxxxxxxx>, "Andy Lee" <andylee@xxxxxxxx>
Subject: RE: [Xen-users] DomU Bridged vs. Routed Networking?
From: "Ian Pratt" <m+Ian.Pratt@xxxxxxxxxxxx>
Date: Wed, 17 Aug 2005 09:30:43 +0100
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Thread-topic: [Xen-users] DomU Bridged vs. Routed Networking?
 

> > Seems like most users opt for the bridged approach.  Perhaps it's 
> > because it is easier to setup and it is the default setting.  For 
> > route, I spent several days to learn that 
> > /proc/sys/net/ipv4/conf/eth0/proxy_arp needs to be set to 0.  It is 
> > not (Debian Sarge).  It should probably be added to 
> > /etc/xen/scripts/network-route.
> > 
> > I also modified scripts/vif-route (using iptables) to forward only 
> > packets belonging to each domU's IP address, thereby 
> preventing domU's 
> > from using IP addresses not assigned to them.  

Please can you post diffs and we'll update the example scripts.

> > With bridge, I'd need 
> > to install etables - one extra program to install and learn.

That's not actually true -- you can use iptables to do packet filtering
in bridge mode. You only need ebtables if you want to do matches on MAC
addrs. 

> There is one other factor which some people have noticed and 
> pointed out on this list: the interface is in promiscuous 
> mode in the bridging scenario, which deteriorates performance.
> Your mileage may vary.

All modern Ethernet networks are switched rather than shared media.
Putting the interface in promiscous mode will make NO difference to
performance unless you have lots of *multicast* traffic on your network
that this host isn't interested in.

Ian

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