[CentOS] Re: alias ip-addresses at loopback

Dmitry Cherkasov doctorchd at gmail.com
Tue Sep 16 05:49:09 UTC 2008


2008/9/15 Robert <kerplop at sbcglobal.net>:
>
>
> Robert Nichols wrote:
>>
>> Dmitry Cherkasov wrote:
>>>
>>> Hello everybody!
>>>
>>> Could anybody advice on the following problem.
>>> I need to assign several ip-addresses to 'lo' interface (beside
>>> 127.0.0.1). It is convenient to me to implement NAT with such
>>> addresses.
>>
>> The "lo" interface already accepts packets with any 127.x.y.z
>> address.  Do you really need more addresses than the 127.0.0.0/8
>> block?
>>
>>    $ ping -c1 127.111.222.123
>>    PING 127.111.222.123 (127.111.222.123) 56(84) bytes of data.
>>    64 bytes from 127.111.222.123: icmp_seq=1 ttl=64 time=0.104 ms
>>
>> I did absolutely nothing special to set that up.  I also routinely
>> have an stunnel process listening on 127.0.0.25:465, and again, I
>> did nothing special with the interface configuration or routing
>> tables to allow that to work.
>
> Any doubter can demonstrate that easily:
> -----------
>
> #!/bin/bash
> #
> z=1;y=0;x=0
> while [ $x -le 255 ] ; do
> y=0
> while [ $y -le 255 ] ; do
> z=1
> while [ $z -le 255 ] ; do
>  ping -c1 127.$x.$y.$z
> (( z +=1 ))
> done
> (( y +=1 ))
> done
> (( x +=1 ))
> done


Theoretically 'fping -g 127.0.0.0/8' does the same yet it consumes too
much memory.
My box with 512MB of RAM didn't manage to execute this ;-)



> ---------------------
> <snip>
> PING 127.5.139.115 (127.5.139.115) 56(84) bytes of data.
> 64 bytes from 127.5.139.115: icmp_seq=1 ttl=64 time=0.051 ms
>
> --- 127.5.139.115 ping statistics ---
> 1 packets transmitted, 1 received, 0% packet loss, time 0ms
> rtt min/avg/max/mdev = 0.051/0.051/0.051/0.000 ms
> PING 127.5.139.116 (127.5.139.116) 56(84) bytes of data.
> 64 bytes from 127.5.139.116: icmp_seq=1 ttl=64 time=0.052 ms
>
> --- 127.5.139.116 ping statistics ---
> 1 packets transmitted, 1 received, 0% packet loss, time 0ms
> rtt min/avg/max/mdev = 0.052/0.052/0.052/0.000 ms
> PING 127.5.139.117 (127.5.139.117) 56(84) bytes of data.
> 64 bytes from 127.5.139.117: icmp_seq=1 ttl=64 time=0.051 ms
>
> --- 127.5.139.117 ping statistics ---
> 1 packets transmitted, 1 received, 0% packet loss, time 0ms
> rtt min/avg/max/mdev = 0.051/0.051/0.051/0.000 ms
> PING 127.5.139.118 (127.5.139.118) 56(84) bytes of data.
> 64 bytes from 127.5.139.118: icmp_seq=1 ttl=64 time=0.051 ms
>
> --- 127.5.139.118 ping statistics ---
> 1 packets transmitted, 1 received, 0% packet loss, time 0ms
> rtt min/avg/max/mdev = 0.051/0.051/0.051/0.000 ms
>
>
> ...etc.
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>



-- 
Dmitry Cherkasov


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