Greetings,
I administrate a server that is currently running Xen 2.0 with six
subdomains and I have a question about running multiple physical networks on
it.
Currently, we have it setup on one physical network using one network bridge
as follows:
Server:~# brctl show
bridge name bridge id STP enabled interfaces
xen-br0 8000.000c76151728 no eth0
vif1.0
vif2.0
vif3.0
vif4.0
vif5.0
vif6.0
However, our colocation host now wants to change us from our current
physical network to a new physical network. I would just simply renumber our
IP addresses at the cost of maybe an hour of downtime, but we have our
primary nameserver running on the server as well. So we opted to try and see
if we could have our Xen machine running on both physical networks at once
with little to no downtime.
Our server has two ethernet ports, so we had our colocation host plug the
second ethernet port in to the new physical network, but now I am unsure
exactly what to do now.
I had thought about making a second bridge (xen-br1) and adding the second
ethernet interface (eth1) to it, and then adding all the virtual interfaces
to it, but I don''t know if you can add the virtual interfaces to more
then
one bridge. I would like to know if something like that would work before
trying it on the production environment.
In short, I would like it so that our server is on two separate physical
networks using two ethernet interfaces, so that we can have our subdomains
binding to IP addresses on both the old physical network and the new
physical network.
Thank you for your help in advance, I would appreciate any help anyone could
offer, or suggestions on what to do.
-Andrew
--
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Hi Andrew, On Feb 23, 2006 11:01 AM, aewert <aewert2@infolaunch.com> wrote:> > Greetings, > > I administrate a server that is currently running Xen 2.0 with six > subdomains and I have a question about running multiple physical > networks on > it. > > Currently, we have it setup on one physical network using one network > bridge > as follows: > > Server:~# brctl show > bridge name bridge id STP enabled interfaces > xen-br0 8000.000c76151728 no eth0 > vif1.0 > vif2.0 > vif3.0 > vif4.0 > vif5.0 > vif6.0 > > However, our colocation host now wants to change us from our current > physical network to a new physical network. I would just simply > renumber our > IP addresses at the cost of maybe an hour of downtime, but we have our > primary nameserver running on the server as well. So we opted to try > and see > if we could have our Xen machine running on both physical networks at > once > with little to no downtime. > > Our server has two ethernet ports, so we had our colocation host plug > the > second ethernet port in to the new physical network, but now I am > unsure > exactly what to do now. > > I had thought about making a second bridge (xen-br1) and adding the > second > ethernet interface (eth1) to it, and then adding all the virtual > interfaces > to it, but I don''t know if you can add the virtual interfaces to more > then > one bridge. I would like to know if something like that would work > before > trying it on the production environment.No, you can''t. You can, however, have two virtual interfaces in each domU, each of which attached to a physical interface.> In short, I would like it so that our server is on two separate > physical > networks using two ethernet interfaces, so that we can have our > subdomains > binding to IP addresses on both the old physical network and the new > physical network.That way you can do it. When moving, it''ll just be a matter of changing the default route in your VM''s. rgrds, Braulio Gergull _______________________________________________ Xen-users mailing list Xen-users@lists.xensource.com http://lists.xensource.com/xen-users
Perhaps I should outline my idea with a bit more detail. I want to migrate my Xen server from one physical network to another physical network over the course of a week. To do this, I want to have my DomU''s running able to bind to an IP address on both physical networks so the transition is seemless. Currently its set up with one bridge (xen-br0) which is bound to our primary ethernet interface eth0, which is connected to our old subnet. I was thinking about creating a secondary bridge (we''ll call it xen-br1) and attach my second ethernet interface eth1 (which is on the new physical subnet) to it. The original bridge(xen-br0, which is attached to eth0 which is on the old physical subnet) would remain untouched. Then I had planned to set up this second bridge interface(xen-br1) with a default route on the new subnet, and for each DomU I would have it create two virtual network interfaces using the following line in each domain config file: vif = [ ''bridge=xen-br0'', ''bridge=xen-br1'' ] Then would I be able to use the first virtual interface in each DomU to access the old subnet, and the second virtual interface in each DomU to access the new subnet? I am concerned that this might create conflicting route-table entries. If I add a virtual interface from each DomU to both bridges, is Xen going to be able to know which route to use for incoming and outgoing traffic, or do I need to use some other means of NAT along with this? I appreciate Braulio''s suggestion to change the default routes using two different interfaces, but I''m still unsure how Xen will respond to this. Again, I am running Xen-2.0 and have 6 DomU machines running on my server. Will this idea work, if not is there a better way to do this? I''m looking for a specific example if possible. Any suggestions or ideas are very much welcome. Thanks in advance! -Andrew -- View this message in context: http://www.nabble.com/Xen-using-Multiple-Network-Cards-t1175293.html#a3097935 Sent from the Xen - User forum at Nabble.com. _______________________________________________ Xen-users mailing list Xen-users@lists.xensource.com http://lists.xensource.com/xen-users
Hi Andrew, On Feb 23, 2006 06:25 PM, aewert <aewert2@infolaunch.com> wrote:> > Perhaps I should outline my idea with a bit more detail. > > I want to migrate my Xen server from one physical network to another > physical network over the course of a week. To do this, I want to have > my > DomU''s running able to bind to an IP address on both physical networks > so > the transition is seemless. Currently its set up with one bridge > (xen-br0) > which is bound to our primary ethernet interface eth0, which is > connected to > our old subnet.Ok.> I was thinking about creating a secondary bridge (we''ll call it > xen-br1) and > attach my second ethernet interface eth1 (which is on the new physical > subnet) to it. The original bridge(xen-br0, which is attached to eth0 > which > is on the old physical subnet) would remain untouched.Ok.> Then I had planned to set up this second bridge interface(xen-br1) > with a > default route on the new subnet,Not exactly, default route is related to the TCP/IP stack of the OS (be it real or virtual). You can thus have only one default route per machine (unless you use advanced routing, which is not the case here).> and for each DomU I would have it create > two virtual network interfaces using the following line in each domain > config file: > > vif = [ ''bridge=xen-br0'', ''bridge=xen-br1'' ]That''s fine.> Then would I be able to use the first virtual interface in each DomU > to > access the old subnet, and the second virtual interface in each DomU > to > access the new subnet?Sure.> I am concerned that this might create conflicting route-table entries.No, it won'' t. You''ll end up with somethind like: Destination Gateway Genmask Flags Metric Ref Use Iface old_network 0.0.0.0 255.255.255.0 U 0 0 0 eth0 new_network 0.0.0.0 255.255.0.0 U 0 0 0 eth1 0.0.0.0 old_net_gw 0.0.0.0 UG 0 0 0 eth0 For either dom0 and domU''s. Default route will still be pointing the old network gateway.> If I > add a virtual interface from each DomU to both bridges, is Xen going > to be > able to know which route to use for incoming and outgoing traffic, or > do I > need to use some other means of NAT along with this?You just can''t do that, the kernel won''t let you add an interface to more than one bridge. And even if you could, it wouldn''t work anyway.> I appreciate Braulio''s suggestion to change the default routes using > two > different interfaces, but I''m still unsure how Xen will respond to > this.Xen is not concerned about that at all, it will just create the virtual interfaces and enable them for you to use the way you want. Even the bridges are created by helper scripts, not by Xen itself.> Again, I am running Xen-2.0 and have 6 DomU machines running on my > server. > > Will this idea work, if not is there a better way to do this? I''m > looking > for a specific example if possible.It''ll work just as if you had a physical machine with two real network cards, each connect to one network and the default gateway pointing to the old network gateway. When you want to move you just replace the default route pointing to the new network gateway. Hope that it helps. rgrds, Braulio Gergull _______________________________________________ Xen-users mailing list Xen-users@lists.xensource.com http://lists.xensource.com/xen-users