Here's a tested combination of settings, assuming that the kernel has netconsole support compiled in (not a module):
In /etc/lilo.conf, the section may look like:
image=/boot/vmlinuz-2.6.18-194.8.1.el5.028stab070.2.owl3
label=070.2.owl3
append="panic=10 netconsole=444@192.168.xxx.src/eth1,666@192.168.xxx.dst/00:11:22:33:44:55"
Of course, proper source IP address, interface name, and destination IP address and MAC address (same Ethernet segment/VLAN) need to be substituted.
On the temporary logging server, run (preferably under screen):
nc -vul 666 | tee -a netcons-srcservername
Tested with OpenBSD-derived netcat that we have in Owl.