Public IP on loop back interface

[Mike Kallies]

It's sometimes used in mac-based load balancing.

You add the shared IP to the loopback.  Then when a frame hits your
server with the destination IP address, the packet happily goes up the
stack.  The reply packet goes out the normal route because it doesn't
care about the source mac.

( Linux sometimes needs some ARP trickery or a custom kernel to prevent
it from advertising the address though. )

... but I can't think of any other reason.



On 16/04/2012 9:32 PM, James Knott wrote:
> William Muriithi wrote:
>> Evening pal,
>>
>> I am curious, have anybody ever seen a system using a public IP for
>> loop back interface instead of 127.0.0.1?
>>
>> Would there be a good reason to do that?
>>
>> Regards,
>>
>> WIlliam
>>
> 
> I have never seen that and can't think of a reason for doing it.  On the
> other hand I can think of reasons for not doing it.  The loop back is
> always supposed to be 127.x.x.x on IPv4 and ::1 on IPv6.
> 
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