[tech] New gear

[Adrian Chadd]

On Sun, Jan 18, 2009, James Andrewartha wrote:

> No, the problem is VLANs - configuring them in Xen is a right PITA.

The problem is distributions and the order in which they bring up interfaces.


What I do under Fedora Core and CentOS:

* eth0 stays management, for dom0. I let the silly Xen script work on that
* eth1 is for vlans. I have a custom script which just sets up the bridging
  seperately, ignoring the xen scripts
* I then create bridges, name them xenbrX.Y, and Xen domU's just work with them.

The trouble is the order in which the vlan interfaces and the xen startup happen.
If the Xen scripts clone the interface and then you create vlan subif's off the
"virtual" ethernet (ie, not pethX) then none of your bridge interfaces work
correctly.

Of course, you could also just use eth0 + vlans, by making eth0 mgmt only, not
configuring a network script (or configuring a null one) so it doesn't setup
eth0 "magically", and then hard-code into your config vlan subif's and bridge
interfaces.

Also, of course, some distributions (hai debian!) don't like you bringing up an
interface with no IP address, kjust so you can use it as a bridging interface.
I'd love to know how to tell ifup/ifdown to do this without putting in fake
IP's into the interface. (hint: 0.0.0.0 doesn't work in all distributions.)

2c,


Adrian