[CentOS-virt] routing problem with domU bridged to two networks
Ed at Heron-ent.com
Wed Mar 7 15:18:00 EST 2012
On Wed, 2012-03-07 at 13:13 -0700, Ed Heron wrote:
> On Wed, 2012-03-07 at 20:41 +0200, Peter Peltonen wrote:
> > As I received no response on the general CentOS list, I'll repost it
> > here as the question is about Xen virtual machine routing.
> > This is my network setup:
> > http://pastebin.com/kyWpTQYU
> > Lets assume my dom0's eth2 public ip is 18.104.22.168 and my dmz network
> > 22.214.171.124/255.255.255.224 . I have created NAT from my LAN with
> > iptables. You can see my /etc/sysconfig/iptables here:
> > http://pastebin.com/1FqSTvPH
> > And this is my dom0 routing table:
> > http://pastebin.com/gNjTFHp5
> > My goal:
> > To access NFS shares on a (non-virtualized) file server in the LAN
> > network from the domU web server in the DMZ network.
> > What I tried:
> > I attached the domU to both bridges using this Xen config:
> > vif = [ "mac=00:0c:29:de:3a:fe,bridge=xenbr0","mac=00:0C:29:76:19:85,bridge=xenbr1"
> > ]
> > and then created two eth interfaces inside the domU mapping to the MAC
> > addresses above, giving eth1 an IP from the DMZ (126.96.36.199) and
> > giving eth2 an IP from the LAN (192.168.0.12). After this I mounted
> > the NFS share from the file server (192.168.0.2).
> > My problem:
> > If my domU web server is connected to both LAN and DMZ using the two
> > bridges xenbr0 and xenbr1, I can access the NFS share from the domU
> > web server and everything else works as expected, except for one thing
> > -- my workstations in the LAN cannot anymore access the web server:
> > web pages do not open anymore and from the workstations I cannot ping
> > the domU. If the web server domU is only connected to DMZ via xenbr0,
> > the workstations can access it ok.
> > Any advice what I am doing wrong and I could fix my setup?
> The postrouting command uses -o eth2. To NAT LAN requests to your DMZ
> web server, shouldn't you be using xenbr0?
> Though, I would bridge eth2, as well, and create a virtual firewall
> with eth0 (DMZ?), eth1 (LAN) and eth2 (PUB). I wouldn't want the Dom0
> to be directly compromised if my firewall was compromised.
I'd also add a fourth network interface for SAN, then you can connect
2 virtual servers together and use DRBD to replicate your disk space for
fault tolerance. Your firewall could be started on either machine.
> > Regards,
> > Peter
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