First, install the iscsi-initiator-utils package using:

yum install iscsi-initiator-utils

Next, start the iscsid service and enable it to start when the system boots:

service iscsid start
chkconfig iscsid on

Then obtain a listing of available targets from a given host (please note that ipaddress listed below must be replaced with the resolvable hostname or ip address of the system providing the port if different than default):

iscsiadm -m discovery -t sendtargets -p ipaddress

Finally, use the following command to login to the available target (again, replace targetname with one from the output of the previous command and replace ipaddress below with that of the target system):

iscsiadm -m node -T targetname -p ipaddress -l

This will enable the target to be accessed upon reboots and it stores it in a node database found in /var/lib/iscsi that is more thoroughly described in the /usr/share/doc/iscsi-initiator-utils-VERSION/README file.

For a more verbose listing of possible options for the iscsiadm command in Red Hat Enterprise Linux 5 refer to the manual page using:

man iscsiadm

For a good overview of iscsi in Red Hat Enterprise Linux 5 refer to the documenation provided in /usr/share/doc/iscsi-initiator-utils-VERSION/README.