[Hampshire] ifconfig eth0 1500

OK, I managed to omit the mtu setting on the following ifconfig command...

simon-desktop:/home/simon# ifconfig eth0 1500

Expecting to get a complaint about an invalid setting I instead set the
IP address to 0.0.5.220.

simon-desktop:/home/simon# ifconfig eth0
eth0      Link encap:Ethernet  HWaddr 00:40:63:E6:90:82
           inet addr:0.0.5.220  Bcast:255.255.255.255  Mask:0.0.0.0
           inet6 addr: fe80::240:63ff:fee6:9082/64 Scope:Link
           UP BROADCAST RUNNING MULTICAST  MTU:1400  Metric:1
           RX packets:9478291 errors:1396 dropped:0 overruns:0 frame:0
           TX packets:8721187 errors:0 dropped:0 overruns:0 carrier:0
           collisions:0 txqueuelen:1000
           RX bytes:3334208705 (3.1 GiB)  TX bytes:1438281358 (1.3 GiB)
           Interrupt:169 Base address:0xf800

Obviously it was easy to put back but I would love to know why/if this
is defined behaviour.

Simon