Here are the variables that dhclient sets and are usable by dhclient-scripts. I created this list by create the file “/etc/dhclient-exit-hooks” and adding the following lines to it :

echo "----printenv-----" >>/tmp/dhclient.out
printenv >> /tmp/dhclient.out
echo "----set-----" >>/tmp/dhclient.out
set >> /tmp/dhclient.out

These are the variables revealed by printenv.

old_subnet_mask=255.255.248.0
old_domain_name_servers=10.76.232.101 10.76.232.102
old_broadcast_address=10.76.239.255
old_expiry=1266966093
new_subnet_mask=255.255.248.0
new_domain_name=example.com
OLDPWD=/etc/sysconfig/network-scripts
new_ip_address=10.76.237.100
new_network_number=10.76.232.0
interface=eth0
reason=RENEW
old_dhcp_message_type=5
new_expiry=1266966798
PATH=/sbin:/usr/sbin:/bin:/usr/bin
new_dhcp_lease_time=1800
pid=3135
new_dhcp_server_identifier=10.76.232.102
PWD=/etc/sysconfig/network-scripts
LANG=en_US.UTF-8
new_routers=10.76.232.1
new_domain_name_servers=10.76.232.101 10.76.232.102
SHLVL=1
old_dhcp_server_identifier=10.76.232.102
new_dhcp_message_type=5
old_ip_address=10.76.237.100
old_dhcp_lease_time=1800
new_broadcast_address=10.76.239.255
old_network_number=10.76.232.0
old_routers=10.76.232.1
old_domain_name=example.com
_=/usr/bin/printenv