CentOS virt - Dec 2009 - KVM: bridge configuration for static IP address

I need to allocate public IP address to two  guest os.

I have only 2 network card Interface on server. say eth0 and eth1.

I set eth1 a public IP address. so it should in 

# vi /etc/sysconfig/ifcfg-eth1

DEVICE=eth1
BOOTPROTO=static
HWADDR=00:1a:4d:83:ad:00  
BROADCAST=202.127.29.0
IPADDR=202.127.29.5
NETMASK=255.255.255.0
NETWORK=202.127.29.0
ONBOOT=yes
TYPE=Ethernet

Question 1: do I have to add GATEWAY=202.127.29.1 to above setting?
 
now continue to set eth0,seems I would use it as bridge ,so ifcfg-eth0 would be:
# vi ifcfg-eth0
DEVICE=eth0
HWADDR=00:1a:4d:83:ad:50  
ONBOOT=yes
BRIDGE=br0

There's no IP address in this ifcfg-eth0. so 
Question 2: do I need to add the rest 2 IP addresses in br0?  or I should  keep
br0 with no IP address and set IP in guest OS directly?
Could anybody tell me how to set br0 to let host os and 2 guest os all have
their own dedicated IP address?
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----- "rewing" <rewing at howfortune.com> wrote:
> I need to allocate public IP address to two guest os.
> 
> I have only 2 network card Interface on server. say eth0 and eth1.
> 
> I set eth1 a public IP address. so it should in
> 
> # vi /etc/sysconfig/ifcfg-eth1
> 
> DEVICE=eth1
> BOOTPROTO=static
> HWADDR=00:1a:4d:83:ad:00
> BROADCAST=202.127.29.0
> IPADDR=202.127.29.5
> NETMASK=255.255.255.0
> NETWORK=202.127.29.0
> ONBOOT=yes
> TYPE=Ethernet
> 
> Question 1: do I have to add GATEWAY=202.127.29.1 to above setting?
GATEWAY probably belongs in /etc/sysconfig/network...
> Question 2: do I need to add the rest 2 IP addresses in br0?
Nope.
> or I
> should keep br0 with no IP address and set IP in guest OS directly?
Yep. However, if you do that, you will need something acting as the gateway. If
your host is going to be the gateway, it will need an address set in ifcfg-br0
and packet forwarding turned on. If eth1 and br0 are both in the same [public]
network, you should just set the public IP address on br0 and add both eth0 and
eth1 to the bridge and turn on STP.

(I don't see why you need eth0 in this mix at all if you are just using it
for guests on the local machine.)

-- 
Christopher G. Stach II
http://ldsys.net/~cgs/

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>----- "rewing" <rewing at howfortune.com> wrote:
>> I need to allocate public IP address to two guest os.
>> 
> >I have only 2 network card Interface on server. say eth0 and eth1.
> >
> >I set eth1 a public IP address. so it should in
>> 
>> # vi /etc/sysconfig/ifcfg-eth1
> >
> >DEVICE=eth1
> >BOOTPROTO=static
> >HWADDR=00:1a:4d:83:ad:00
> >BROADCAST=202.127.29.0
> >IPADDR=202.127.29.5
> >NETMASK=255.255.255.0
> >NETWORK=202.127.29.0
> >ONBOOT=yes
> >TYPE=Ethernet
> >
> >Question 1: do I have to add GATEWAY=202.127.29.1 to above setting?
>GATEWAY probably belongs in /etc/sysconfig/network...
>> Question 2: do I need to add the rest 2 IP addresses in br0?
>Nope.
>> or I
>> should keep br0 with no IP address and set IP in guest OS directly?
>Yep. However, if you do that, you will need something acting as the gateway.
If your host is going to be the gateway, it will need an address set in
ifcfg->br0 and packet forwarding turned on. If eth1 and br0 are both in the
same [public] network, you should just set the public IP address on br0 and add
both eth0 and eth1 to the bridge and turn on STP.
>(I don't see why you need eth0 in this mix at all if you are just using
it for guests on the local machine.)
>-- 
>Christopher G. Stach II
>http://ldsys.net/~cgs/
Hi,Christopher,

Thanks, But still I'm a little confused.

Actually I don't need host to be a gateway. There're should be gate
way's on that IDC center. So the gate way should be add to
/etc/sysconfig/network, right?

And still, I have 2 ehtnet interface on my mainboard. So I should allocate eth1
an IP address for host, and only make eth0 as br0, and set guest OS IP address
in guest OS network configuration, right?

Please help to check if this is the correct setting as bellow

/etc/sysconfig/ifcfg-eth1
DEVICE=eth1
BOOTPROTO=static
HWADDR=00:1a:4d:83:ad:00
BROADCAST=202.127.29.0
IPADDR=202.127.29.5
NETMASK=255.255.255.0
NETWORK=202.127.29.0
ONBOOT=yes
TYPE=Ethernet

/etc/sysconfig/ifcfg-eth0
DEVICE=eth0
HWADDR=00:1a:4d:83:ad:50  
ONBOOT=yes
BRIDGE=br0

/etc/sysconfig/ifcfg-br0
DEVICE=br0
TYPE=Bridge
BOOTPROTO=none
ONBOOT=yes
DELAY=0

will this work so host os and 2 guest oses all got their IP address? or I should
modify something?
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----- "rewing" <rewing at howfortune.com> wrote:
> Thanks, But still I'm a little confused.
> 
> Actually I don't need host to be a gateway.
How do you expect packets to get from one ethernet interface to the other
without packet forwarding and a gateway on each network?
> And still, I have 2 ehtnet interface on my mainboard. So I should
> allocate eth1 an IP address for host, and only make eth0 as br0, and
> set guest OS IP address in guest OS network configuration, right?
Maybe just add eth1 to br0 and not use eth0?

-- 
Christopher G. Stach II
http://ldsys.net/~cgs/