Make sure you have startup file properly configured. Usually in RedHat we give ONBOOT=y in /etc/sysconfig/network-scripts/ifcfg-ethX. Other vendor may have different options. You can use "Kudzu" or "netconfig" tool.
Also make sure you have eth1 module mentioned in /etc/modprobe.conf or /etc/modules.conf (as per kernel version 2.6 or 2.4 resp)