Loopback IP addresses

barkers · 03-31-2005, 08:45 AM

Hi,

can anyone tell me if all addresses in 127.0.0.* ip range are loopback addresses.
I know that 127.0.0.1 is but can i use 127.0.0.2, 127.0.0.3

Grateful for any help
Thanks
Barclay

mugwump84 · 03-31-2005, 08:59 AM

Just guessing, i'd say no.

barkers · 03-31-2005, 09:20 AM

funny, everyone I've asked has said that. but i can ping them.

frgtn · 03-31-2005, 10:37 AM

Well maybe whole 127.0.0.0/24 subnet is loopback?

I've just done some research, see for yourself:

Code:

Starting nmap 3.75 ( http://www.insecure.org/nmap/ ) at 2005-03-31 19:34 EEST
Host 127.0.0.0 seems to be a subnet broadcast address (returned 1 extra pings).
Host localhost (127.0.0.1) appears to be up.
Host 127.0.0.2 appears to be up.
Host 127.0.0.3 appears to be up.
Host 127.0.0.4 appears to be up.
Host 127.0.0.5 appears to be up.
<...>
Host 127.0.0.254 appears to be up.
Host 127.0.0.255 appears to be up.
Nmap run completed -- 256 IP addresses (255 hosts up) scanned in 44.511 seconds

doctormetal · 03-31-2005, 11:03 AM

Quote:

Originally posted by frgtn
Well maybe whole 127.0.0.0/24 subnet is loopback? I've just done some research, see for yourself:

actually, it is 127.0.0.0/8

Quote:

Code:

Starting nmap 3.75 ( http://www.insecure.org/nmap/ ) at 2005-03-31 19:34 EEST Host 127.0.0.0 seems to be a subnet broadcast address (returned 1 extra pings). Host localhost (127.0.0.1) appears to be up. Host 127.0.0.2 appears to be up. Host 127.0.0.3 appears to be up. Host 127.0.0.4 appears to be up. Host 127.0.0.5 appears to be up. <...> Host 127.0.0.254 appears to be up. Host 127.0.0.255 appears to be up. Nmap run completed -- 256 IP addresses (255 hosts up) scanned in 44.511 seconds

You can try other address too, like 127.254.254.254
It indeed looks like it is all loopback. Result is the same on windows XP.

benjithegreat98 · 03-31-2005, 11:04 AM

It is actually 127.0.0.0/8 that is reserved as the loopback interface.

barkers · 04-01-2005, 02:36 AM

coolio, thanks.

What does it means when you say "27.0.0.0/24 subnet" or "27.0.0.0/8 subnet"?
does that refer to the number of addresses that can be used?
I'm a bit of a newbie to networking.

cheers

frgtn · 04-07-2005, 02:10 PM

the number after the slash means the number of bits from the left that do not change for that subnet:
127.0.0.1/8 means that first 8 bits ( 127 ) is static for this subnet and the rest 24 bits ( 3 numbers ) can vary.