Re: 127.x.x.x

Thanks William.
As you mentioned, I am one of the old timers.
One decade ago, a CCIE showed me ALL IP addresses could be assigned to
the interfaces of the routers in his lab, including
0.0.0.0/8 and 127.0.0.0/8. I regret that we lose the freedom.

Also, thank you for the tip on linux box

Jack

William McCall wrote:
> No.
>
> For at least 2 reasons:
>
> 1) RFC 1700 [1] and RFC 3330 [2] both specify that the 127.0.0.0/8
> should never appear on any network anywhere. Cisco complies with this
> directive [3] in 12.4T (and, I'm willing to bet, most any other
> version of IOS but the old timers can tell me about how 11.0 allowed
> this)
>
> 2) These loopback addresses are used internally for, primarily,
> service modules and linecards (anyone, is there any other place this
> is used?) and would most likely break stuff. For example, attaching to
> a line card on the 12K GSR (IOS, not sure about XR) results in a funky
> telnet connection to an address like 127.0.0.17.
>
> For the scenario you proposed on your Linux box before, you can create
> a sub interface on the loopback interface. Example:
>
> ifconfig lo:0 192.168.12.1 netmask 255.255.255.0
>
> And now you have a new network for handling your terminal server.
>
> HTH

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Received on Wed Apr 21 2010 - 08:38:24 ART