Why is loopback IP address from 127.0.0.1 to 127.255.255.254

ip address

I do know that 127.0.0.1 ~ 127.255.255.254 are the loopback IP addresses for most modern operating systems and we could use these IP addresses to refer to our own computer. But isn't 127.0.0.1 enough?!?! why a wide range? why from 127.0.0.1 to 127.255.255.254?

Best Answer

The 127/8 network can be used for a number of things.

1) Simulating a large number of different computers in a fast network (simply bring up more interfaces and bind services to them) without using virtual machines. This might be helpful if you wanted to have a number of different web servers running locally on port 80 for some reason.

2) Permitting more locally running services than the 64k TCP would permit (though it seems unlikely that you would hit that limit rationally)

3) Playing games with people who aren't familiar with this factoid; "Hey, you're a loser hacker, I bet you can't even hack me. Go ahead and try; I'm at 127.45.209.66"

Probably other things too.

Related Solutions

The need for a secondary IP address

primary and secondary dns server on the same box? not so good idea...

some possible usage:

multiple separate ftp sites. in ftp there is no concept of vhost unless you have couple of ips.
multiple separate https sites. for https each site requires separate ip
maybe virtualization and couple of completly independent servers running on the same platform.

Can an IP address in the private range be used as a public address

Any IP can be routed. But a network admin or an ISP that's worth their salt will block the egress/ingress of packets sourced from or destined for those addresses at the edge of their network.

There is no good that can come of allowing that traffic in or out of your network. Apply:

Extended IP access list 111
    10 deny ip 127.0.0.0 0.255.255.255 any
    20 deny ip 224.0.0.0 31.255.255.255 any
    30 deny ip 10.0.0.0 0.255.255.255 any
    40 deny ip 172.16.0.0 0.15.255.255 any
    50 deny ip 192.168.0.0 0.0.255.255 any

to the outbound interface of your edge router. Reverse for the inbound.

Best Answer

Related Solutions

The need for a secondary IP address

Can an IP address in the private range be used as a public address

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