I am attempting to boot my domain off the ssp and it is timing out on
the rarp request. I have verified that the SSP is configured correctly
to be a boot server (i.e. /etc/ethers,/etc/hosts, nsswitch.conf and 
in.rarpd -a running). What else can be causing this problem?

Check eeprom setting on the domain for this variable at the
ok prompt by typing:

    printenv local-mac-address?

If set to true, set to false by typing following commands:

   setenv local-mac-address? false
   reset

and try booting again. If the SSP is indeed setup correctly, with
the original system MAC address, boot net should now work. 

This variable is often set to true so more then one interface
can be on the same subnet. The side effect is that the interface
uses its onboard MAC address and not the one supplied by system,
thus RARPs from domain are not answered by the SSP.

NOTE:
Be sure to set this back to true once you have finished with
what ever operation(s) you did while booted over the net.    

See the following Sunsolve Documents for more information on setting
multiple MAC address and how this works:

infodoc 17018
        What are the steps in configuring more than one Ethernet interfaces
        connected to same physical subnet

infodoc 15572    
         Can I configure two Ethernet interfaces on the subnet?

infodoc 16733 
        Why do all my ethernet interfaces have the same ether MAC
        address?

For more information on booting over the network see "Sun Enterprise 10K
System Hardware Installation and De-Installation Guide" manual.

Also Sunsolve infodoc 13328 has good jumpstart information.

Since this eeprom change is usually made after the customer
has setup and tested booting from the SSP it is easily overlooked