ping, every 4th packet not reported on

[Lennart Sorensen]

On Mon, Mar 22, 2010 at 03:44:28PM -0400, marthter wrote:
> Hellooo Leenooks users...
>
> I've noticed this for years but finally I can't stand not understanding  
> it any more.  Hopefully someone on here who's better versed with Linux  
> than me can set me straight...
>
> Why is every 4th packet not mentioned in ping results when pinging a  
> non-live address?
>
> i.e. in the icmp_seq numbers below, they go: [no 1], 2, 3, 4, [no 5], 6,  
> 7, 8, [no 9], 10, 11, 12, ...
>
> It seems like the missing numbers will start randomly at either 1, 2, 3,  
> or 4, but then from there onwards it is EVERY 4th one consistently for  
> hundreds or thousands of packets if I let it go.
>
> What does it mean?
>
> Thanks in advance.
>
> Martin
>
>
> [martin at grand ~]$ ping large
> PING large.example.com (192.168.11.11) 56(84) bytes of data.
> From grand.example.com (192.168.11.22) icmp_seq=2 Destination Host  
> Unreachable
> From grand.example.com (192.168.11.22) icmp_seq=3 Destination Host  
> Unreachable
> From grand.example.com (192.168.11.22) icmp_seq=4 Destination Host  
> Unreachable
> From grand.example.com (192.168.11.22) icmp_seq=6 Destination Host  
> Unreachable
> From grand.example.com (192.168.11.22) icmp_seq=7 Destination Host  
> Unreachable
> From grand.example.com (192.168.11.22) icmp_seq=8 Destination Host  
> Unreachable
> From grand.example.com (192.168.11.22) icmp_seq=10 Destination Host  
> Unreachable
> From grand.example.com (192.168.11.22) icmp_seq=11 Destination Host  
> Unreachable
> From grand.example.com (192.168.11.22) icmp_seq=12 Destination Host  
> Unreachable
> ^C
> --- large.example.com ping statistics ---
> 12 packets transmitted, 0 received, +9 errors, 100% packet loss, time  
> 11862ms
> pipe 3
> [martin at grand ~]$

No idea why, but it certainly seems to be the way it is.  It probably
depends on the OS of the router sending you the message.  It certainly
seems to be the way current linux kernels do things.

-- 
Len Sorensen
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