Non-Linode RHEL question

I'm trying to add a 2nd IP address to a network adapter on a physical server.

The machine is running a very old RHEL (v 3). It's at a colo facility, and I don't have easy access to it. I didn't set any of this up – I'm trying to move stuff off of these machines, on to modern boxes.

The box has two NICs built in, and an add in card. The NIC that's being used is the one on the add in card -- no cables are plugged into the others. I want to add the second IP address to the add in card.

The card shows up like this in ifconfig:

dev15200  Link encap:Ethernet  HWaddr 00:10:18:16:4B:BE  
          inet addr:xx.xx.xx.xx  Bcast:xx.xx.xx.xx  Mask:255.255.255.248
          UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
          RX packets:17342787 errors:0 dropped:0 overruns:0 frame:0
          TX packets:14568400 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:1000 
          RX bytes:1706673493 (1627.6 Mb)  TX bytes:42203150 (40.2 Mb)
          Interrupt:10 

Under /etc/sysconfig/network-scripts, I have a file called ifcfg-eth0 that looks like this:

# Broadcom Corporation|NetXtreme BCM5703X Gigabit Ethernet
DEVICE=dev15200
BOOTPROTO=none
BROADCAST=xx.xx.xx.xx
HWADDR=00:10:18:16:4B:BE
IPADDR=128.241.246.164
NETMASK=255.255.255.248
NETWORK=xx.xx.xx.xx
ONBOOT=YES
TYPE=Ethernet
GATEWAY=xx.xx.xx.xx

I know how to set up eth0:0 if eth0 already exists. But I'm not sure how to set it up in this situation, or how to set up a dev15200:0. I've tried a couple of ifcfg-eth0:0 config files – one with the device name eth0:0, and one with the device dev15200:0.

Is there a way to do this?