Found the solution to my problem, and thought I would post it in case I forget it and have to look it up again.. 
Since the customer application was setup to print to 4 individual printers, using 4 different IP addresses, I had the network folks re-map the NATting to point to aliases created on my print queue box. So I created the network aliases on my primary interface, giving me:
eth0 Link encap:Ethernet HWaddr 00:24:E8:67:E9:85
inet addr:172.19.2.56 Bcast:172.19.2.63 Mask:255.255.255.224
inet6 addr: fe80::224:e8ff:fe67:e985/64 Scope:Link
UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1
RX packets:68965 errors:0 dropped:0 overruns:0 frame:0
TX packets:77371 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:1000
RX bytes:26198783 (24.9 MiB) TX bytes:35977262 (34.3 MiB)
Interrupt:169 Memory:f8000000-f8012100
eth0:1 Link encap:Ethernet HWaddr 00:24:E8:67:E9:85
inet addr:172.19.2.57 Bcast:172.19.2.63 Mask:255.255.255.224
UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1
Interrupt:169 Memory:f8000000-f8012100
eth0:2 Link encap:Ethernet HWaddr 00:24:E8:67:E9:85
inet addr:172.19.2.58 Bcast:172.19.2.63 Mask:255.255.255.224
UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1
Interrupt:169 Memory:f8000000-f8012100
eth0:3 Link encap:Ethernet HWaddr 00:24:E8:67:E9:85
inet addr:172.19.2.59 Bcast:172.19.2.63 Mask:255.255.255.224
UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1
Interrupt:169 Memory:f8000000-f8012100
Next was to create the print queues and point them to the HP printers to be serviced. I called them 'printer1' 'printer2' and so on.. (I cheated and did this with Webmin):
[root@ndh1-dmz-ptq ~]# lpstat -a
printer1 accepting requests since Sat 07 Nov 2009 12:30:10 PM EST
printer2 accepting requests since Sat 07 Nov 2009 12:30:14 PM EST
printer3 accepting requests since Sat 07 Nov 2009 12:30:18 PM EST
printer4 accepting requests since Sat 07 Nov 2009 12:30:22 PM EST
[root@ndh1-dmz-ptq ~]#
Verified the existence of the JetDirect service in /etc/services on port 9100:
jetdirect 9100/tcp laserjet hplj #
Installed xinetd on the RHEL 5 system and created a new file in /etc/xinetd.d/ for each print queue that I wanted to setup. Remember to change the name of the print queue and the IP address to be listened to using the BIND flag. This one is called /etc/xinetd.d/printer1:
# Allow applications using the AppSocket / JetDirect protocol
# to communicate with CUPS.
service jetdirect
{
socket_type = stream
protocol = tcp
wait = no
user = lp
server = /usr/bin/lp
server_args = -d printer1 -o raw
groups = yes
disable = no
bind = 172.19.2.56
}
Then I just created 3 more files (one for each printer), restarted xinetd:
service xinetd restart
And check netstat for listeners:
netstat -a|more:
Active Internet connections (servers and established)
Proto Recv-Q Send-Q Local Address Foreign Address State
tcp 0 0 ndh1-dmz-ptq.:2208 *:* LISTEN
tcp 0 0 172.19.2.59:jetdirect *:* LISTEN
tcp 0 0 172.19.2.58:jetdirect *:* LISTEN
tcp 0 0 172.19.2.57:jetdirect *:* LISTEN
tcp 0 0 172.19.2.56:jetdirect *:* LISTEN
tcp 0 0 :sunrpc *: LISTEN
tcp 0 0 :ndmp *: LISTEN
After this we just had to ensure all firewall rules allowed port 9100 traffic to flow in and out, and we were up and printing.
Shawn