Hi guys,

I need to setup 2 additional IPs on a single NIC. Since this is a live box to which I presently have SSH access only, I need to be really careful doing this, so I thought I'd better ask.

CentOS 4.2.

What I have learned until now (correct me if wrong) is that

eth0 ---> remains as is, with the main IP and with /etc/sysconfig/network-scripts/ifcfg-eth0 staying as is with settings:

DEVICE=eth0
BOOTPROTO=static
BROADCAST=BOX.BROAD.CAST.ADDRESS
HWADDR=00:10:2E:61:8B:AA
IPADDR=MAIN.BOX.IP.ADDRESS
NETMASK=255.255.255.0
NETWORK=NET.WORK.IP.ADDRESS
ONBOOT=yes
TYPE=Ethernet, and

eth0:0 with /etc/sysconfig/network-scripts/ifcfg-eth0:0 and
eth0:1 with /etc/sysconfig/network-scripts/ifcfg-eth0:1

for additional (aliased) IPs, with the difference in only the DEVICE= and IPADDR= lines.

Do I create the virtual interfaces using the

ifconfig eth0:0 IP.ADDRESS.NUMBER.2 \ netmask 255.255.255.0 up and
ifconfig eth0:1 IP.ADDRESS.NUMBER.3 \ netmask 255.255.255.0 up commands?

I have checked the kernel's .config, the ip_alias wasn't compiled in, so I believe I would have to load it? Do I need it? If needed, how to load it and make it load on boot?

Do I need to set the routes up like:

/sbin/route add -net 127.0.0.0
/sbin/route add -net MAIN.BOX.IP.ADDRESS dev eth0
/sbin/route add -host MAIN.BOX.IP.ADDRESS dev eth0
/sbin/route add -host IP.ADDRESS.NUMBER.2 dev eth0:0
/sbin/route add -host IP.ADDRESS.NUMBER.3 dev eth0:1
/sbin/route add default gw GATE.WAY.BOX.IP ?

Is this correct? What needs to be changed/corrected/omitted/done?

Please be kind and give me a hand, I have read several different HOWTOs and I am still not sure what to do?

you shouldn't need to directly mess with your routing table, just the additional icfg files should be required. infact you don't need to do that to test if it works or not, just use ifconfig to add additional IP's. "ifconfig eth0:1 192.168.0.2/24" etc... if that works then firm it up with the persistent config files.

Thanks acid_kewpie, I have just tested this on my local CentOS box I am connecting to from the other box with SSH. Entered ifconfig as you proposed, pinged from the other box... working perfectly. Added the ifcfg-eth0:1, rebooted, works perfectly.

So simple...

Thanks a lot, you have helped me a lot!