icmp-host-unreachable as opposed to destination-unreachable

icmp-host-unreachable as opposed to destination-unreachable

[bclark]

Hi all

Would anyone be kind to explain why would a person reject a connection to port 113 with icmp-host-unreachable as opposed to destination-unreachable.
I probally dont understand the difference.
Just something I was wondering.

Kind Regards
Brent Clark

RE: icmp-host-unreachable as opposed to destination-unreachable

[Derick Anderson]

 

> -----Original Message-----
> From: netfilter-bounces@lists.netfilter.org 
> [mailto:netfilter-bounces@lists.netfilter.org] On Behalf Of bclark
> Sent: Tuesday, March 07, 2006 6:45 AM
> To: netfilter@lists.netfilter.org
> Subject: icmp-host-unreachable as opposed to destination-unreachable
> 
> Hi all
> 
> Would anyone be kind to explain why would a person reject a 
> connection to port 113 with icmp-host-unreachable as opposed 
> to destination-unreachable.
> I probally dont understand the difference.
> Just something I was wondering.
> 
> Kind Regards
> Brent Clark
> 

From what I can tell, icmp-host-unreachable is a code (1) for the
destination-unreachable ICMP type (3). See
http://www.spirit.com/Resources/icmp.html for a little more information,
and Google RFC 792 for a lot more information.

Basically though, "host-unreachable" is more specific than
"destination-unreachable". I would think that code 3 would be more
appropriate ("port unreachable") to this specific rule but then I don't
bother with ident (port 113) rules. There's more information on that on
this page: http://grc.com/port_113.htm.

Derick Anderson

RE: icmp-host-unreachable as opposed to destination-unreachable

[Martijn Lievaart]

Derick Anderson zei:
>
>
> bclark said:

>> Hi all
>>
>> Would anyone be kind to explain why would a person reject a
>> connection to port 113 with icmp-host-unreachable as opposed
>> to destination-unreachable.
>> I probally dont understand the difference.
>> Just something I was wondering.
>>
>> Kind Regards
>> Brent Clark
>>
>
>>From what I can tell, icmp-host-unreachable is a code (1) for the
> destination-unreachable ICMP type (3). See
> http://www.spirit.com/Resources/icmp.html for a little more information,
> and Google RFC 792 for a lot more information.
>
> Basically though, "host-unreachable" is more specific than
> "destination-unreachable". I would think that code 3 would be more
> appropriate ("port unreachable") to this specific rule but then I don't
> bother with ident (port 113) rules. There's more information on that on
> this page: http://grc.com/port_113.htm.

Actually one should respond with a tcp reset to tcp/113. All icmp
*-unreachable replies can (and do) give differing results on different
sending tcp stacks.

HTH,
M4