A pretty common and very frustrating problem for people trying to jumpstart unfortunately.

There's a few paths to take to debug, the first test would be to check that you _really_ have the right MAC address in /etc/ethers - sparc systems have a 'use_local' prom setting (or something similar, I forget the exact wording of it) that can override the NIC's MAC with it's hostid. It's used to stop a NIC change from messing with a MAC.

Another thing to check is that you arp daemon is actually running, along with a tfpd. I generally just run the setup_install_server script again if I'm having trouble - it beats thinking too hard

Also check out your /etc/bootparams - that's what actually gets used so it's the 'one true source' of config.

Finally, if none of this is getting you anywhere (or if it'll take you more than about an hour to do), use snoop (or tcpdump if you don't have snoop) on your jumpstart server to watch for the arp/rarp requests and see what your server is actually saying. Check the MAC matches what you thought, see if your jumpstart is answering at all. This will help you nail down what phase of the jumpstart is going wrong. 9 times out of 10, it's the initial rarp getting ignored by the jumpstart server that causes issues.

Failing that, grab a copy of Jet (aka Quark) from sun (I'm pretty sure it's free). It provides heaps of functionality including a manager program to sort out your js server properly.