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Re: [Xen-users] dom0 eth0:0, eth0:1, eth0:2 network setup alias ips

On Wed, Mar 24, 2010 at 11:23 PM, Dan Waterloo <dan@xxxxxxx> wrote:
> Thanks, here's what I'm trying to do:
> 1. consolidate 8 or so servers into one xen box (dual quad core, 20gb RAM,
> two gigabit network ports)
> I have three separate internet connections, and a lan:
> a. dsl line, with 5 fixed ip addresses, a default gateway, and dns
> b. cable modem #1, with a unique set of 5 fixed ip addresses, a default
> gateway, and dns
> c. cable modem #2, with a unique set of 5 fixed ip addresses (different from
> cable modem #1), and a default gateway (different from cable modem #1), and
> dns settings
> d. a private lan, with 192.168.0.xxx, a default gateway, and dns of one of
> the cable modems.

So 4 different networks?

> I have xen domu's that need to be configured with one or two ethernet ports.
> (this part I've figured out how to do)
> a. one configuration is with two network connections, one to a public IP (i
> have boxes that need to be on any one of the three public ip sets (a., b.,
> c.) , and have a private IP on my lan
> b. the other configuration is for private "LAN only" connections.
> The problem I'm having is that I have only two gigabit ethernet ports on my
> new server, so I want to setup the public ips (three sets), on one of the
> physical ports, and the lan on the other physical port.

I highly suggest you take a look at vlans. You might need to also
purchase a vlan-capable switch though. It's pretty affordable

> XEN wants to take over the network configuration,

For complex configuration, I highly suggest you do NOT use xen's
default network-bridge script. Instead, you should disable it on
xend-config.sxp, and create bridges manually using OS config scripts

> and I can get only one of
> the public ip sets to work at a time on the 'public' ethernet port. i.e.,
> either public ips a, or b, or c work, because I can only setup one 'default
> gateway' on the physical port.

That's not xen limitation. It's a general OS limitation. You can only
have one default gateway.

> My thinking is that either this is not possible to do (limitations of mac
> hardware addresses, etc, and the cablemodem/routers),  or I need to do some
> 'fancy footwork' of setting up the network manually.

Some big customers uses BGP for that, but that'd be out of your league :P

> About the only solution that I can visualize is to have the physical port
> NOT to have an IP assigned, and hook it to multiple (3)  Dom0 bridges, each
> bridge would be assigned one of the three sets of ip addresses/gateway, and
> then configure the domUs to one of the three dom0 bridges, based on the ip
> address that it needs to have.

vlans would work. For example:
- eth0 is split into 3 vlans: vlans 101, 102, and 103
- create a bridge on top of each vlans: br101, br102, br103. See
for example.
- assume dom0 only needs to be on one network (br101). So you give IP
address for dom0 on that bridge, while other bridges are up without IP
address on dom0
- assign each domU on whichever bridge you need, based on the ip
address that it needs to have.


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