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Wikipedia has this to say about the loopback address

Various IETF standards reserve the IPv4 address block 127/8 (from which 127.0.0.1 is most commonly used), the IPv6 address ::1, and the name localhost for this purpose.

So any address in the 127.255.255.255 subnet should comply? However OS-X (10.8.5) only responds to pings on 127.0.0.1

$ ping 127.0.0.1
PING 127.0.0.1 (127.0.0.1): 56 data bytes
64 bytes from 127.0.0.1: icmp_seq=0 ttl=64 time=0.050 ms
64 bytes from 127.0.0.1: icmp_seq=1 ttl=64 time=0.077 ms
^C

$ ping 127.1.2.3
PING 127.1.2.3 (127.1.2.3): 56 data bytes
Request timeout for icmp_seq 0
Request timeout for icmp_seq 1
^C

Linux (an old Ubuntu 10.04 VM) responds from the supplied address

$ ping 127.1.2.3
PING 127.1.2.3 (127.1.2.3) 56(84) bytes of data.
64 bytes from 127.1.2.3: icmp_seq=1 ttl=64 time=0.088 ms
64 bytes from 127.1.2.3: icmp_seq=2 ttl=64 time=0.022 ms
^C

While Windows (XP) responds always from 127.0.0.1

C:\>ping 127.1.2.3

Pinging 127.1.2.3 with 32 bytes of data:

Reply from 127.0.0.1: bytes=32 time<1ms TTL=128
Reply from 127.0.0.1: bytes=32 time<1ms TTL=128

Is OS-X not conforming to the standards here? What about XP?

share|improve this question
    
Seems this is related superuser.com/q/458875/8987 and indicates that OS-X is not conforming - so what about XP? –  Peter Gibson Feb 13 '14 at 23:01

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