>It's the entire class! When this was done, people didn't thing that Internet
>would grow so much and address space was considered to be enormous, so they
>just decide to reserve the entire class for loopback..
>
>Ednilson Rosa
I stand corrected, although I have seen router implementations that
will only trash 127.0.0.1 specifically. From RFC 1812:
5.3.7 Martian Address Filtering
An IP source address is invalid if it is a special IP address, as
defined in 4.2.2.11 or 5.3.7, or is not a unicast address.
An IP destination address is invalid if it is among those defined as
illegal destinations in 4.2.3.1, or is a Class E address (except
255.255.255.255).
A router SHOULD NOT forward any packet that has an invalid IP source
address or a source address on network 0. A router SHOULD NOT
forward, except over a loopback interface, any packet that has a
source address on network 127. A router MAY have a switch that
allows the network manager to disable these checks. If such a switch
is provided, it MUST default to performing the checks.
A router SHOULD NOT forward any packet that has an invalid IP
destination address or a destination address on network 0. A router
SHOULD NOT forward, except over a loopback interface, any packet that
has a destination address on network 127. A router MAY have a switch
that allows the network manager to disable these checks. If such a
switch is provided, it MUST default to performing the checks.
If a router discards a packet because of these rules, it SHOULD log
at least the IP source address, the IP destination address, and, if
the problem was with the source address, the physical interface on
which the packet was received and the Link Layer address of the host
or router from which the packet was received.
>
>----- Original Message -----
>From: "Howard C. Berkowitz"
>To:
>Sent: Sunday, August 26, 2001 10:01 PM
>Subject: Re: TCP/IP question [7:17343]
>
>
>>there was a question regarding 127.0.0.1. I understand that the actual
>>TCP/IP "software" actually uses this address for self testing.
>>when ping localhost {or computer {netbios} name} the actual ip address of
>>127.0.0.1 shows up on the screen.
>>
>>In doing some research one book explains that 127.0.0.1 is not useable but
>>the rest of the addresses in the 127 network can be used.
>>I went to my trusty 2500 and try to plug in 127.12.12.25 and the router
>>would not allow me config the interface with that address.
>>
>>Is entire 127 network off limits or just 127.0.0.1. is this a cisco thing.
>>any explaination is appreicated..
>
>
>See RFC 1812. It's only defined to be the one address, but most
>implementations block the 127 network.
>
>>
>>Thank You..
>>
>>Rico Ortiz,
>>Regional Systems Manager,
>>Electronic Support Detachment New York
>>United States Coast Guard
Message Posted at:
http://www.groupstudy.com/form/read.php?f=7&i=17386&t=17343
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