Answer by lkraav for dnsmasq: mapping 2 MAC addresses to the same IP address

(random semi-opinionated comment: it's rare to see this highish count of unconstructive and plain inaccurate answers and comments to a question)

In contrast to others here, I claim that your request is actually quite elementary and has been supported in dnsmasq since version 2.46, IIRC. This was the sole reason I switched from dd-wrt. After about a year of running OpenWRT, I now know there are actually plenty more reasons to switch, but that's beside the point.

I'm running Backfire 10.04-rc4:

May 23 17:45:16 gateway dnsmasq[1925]: started, version 2.55 cachesize 150

My configuration:

$ cat /etc/config/dhcpconfig 'dnsmasq'    option 'domainneeded''1'    option 'boguspriv''1'    option 'localise_queries''1'    option 'rebind_protection''1'    option 'rebind_localhost''1'    option 'expandhosts''1'    option 'authoritative''1'    option 'readethers''1'    option 'leasefile''/tmp/dhcp.leases'    option 'resolvfile''/tmp/resolv.conf.auto'    option 'enable_tftp''1'    option 'domain''domain.net'    option 'local''/domain.net/'config 'dhcp''lan'    option 'interface''lan'    option 'start''100'    option 'limit''150'    option 'leasetime''infinite'config 'dhcp''wan'    option 'interface''wan'    option 'ignore''1'    option 'dynamicdhcp''0'config 'dhcp'    option 'interface''dmz'    option 'start''100'    option 'limit''150'    option 'leasetime''12h'config 'host'    option 'name''travelmate'    option 'mac''00:11:22:33:44:55 aa:bb:cc:dd:ee:ff'    option 'ip''192.168.1.111'config 'host'    option 'name''mobilitymac'    option 'mac''99:88:77:66:55:44 ff:ee:dd:cc:bb:aa'    option 'ip''192.168.1.104'

Enjoy the seamless transition this setup provides, all existing session stay alive if you don't take too long with the switch.