Try booting your system as you noted, then run 'netconfig' as root. That will do a modprobe to attempt to load and configure your system to use the proper modules and then you will be allowed to set your system for DHCP by simply checking your box.
It could be that your system is just waiting to time out for DHCP requests, indicating a network misconfiguration or problem, or that your system is not loading the proper modules for this card.
OR that the module it is trying to load is somehow hanging the machine.
If you are using the Allied Telesyn 2500, their website lists that device as only have "Limited Support" under Linux and they don't list a Linux driver for that card under their current drivers. I didn't find anything under their legacy section either.
However, the Redhat site shows that the Redhat v7.1 comes with a driver for your card (assuming its the AT-2500TX) and the proper module is 'rtl8139.o'
I have a RedHat v7.1 system here, but I don't see that module in '/lib/modules/2.4.2-2/kernel/drivers/net' which is where it should be. That could just mean that I didn't install it. I don't remember. Check that directory for the file on your system. If its there, an 'insmod rtl8139' should load it right up. But 'netconfig' should do that for you.
It appears that the driver is from Realtek and I found some info at http://www.realtek.com.tw/htm/downlo...?model=RTL8139
(A/B/C/8130)/810X%20Family&category=2#Unix about it, but it might involve compiling the driver from source or recompiling your kernel or both.
Unless you are running a custom kernel, I think the install of RHv7.1 uses kernel-2.4.2-i386-smp. That kernel, according to the config file, has modular support for the 8139 card, so the module should load right up.. IF you can find it.
CORRECTION: Okay.. this is kind of weird, the Redhat page mentions the module I wrote above, but I found a module on my system called '8139too.o'
When I go to the kernel source and read the notes on this driver, it says that its the Realtek 8139 module. Hrmm... Look for that one too.