Jeffrey Goldberg wrote:
> My firewall logs are filled with message like
> 
>   ipmon[85]: 18:52:39.107683 sis1 @0:18 b 196.28.87.75 ->
>      72.64.118.118 PR icmp len 20 56 icmp unreach/port
>      for 72.64.118.118,123 - 196.28.87.75,123
>      PR udp len 20 76 IN
> 
> 72.64.118.118 is my pool server.
> 
> I am accepting udp packets for destination port 123 and everything  
> seems to be working correctly, but I don't understand what these ICMP  
> packets are about.   No doubt this reflects my substantial ignorance  
> of IP, but I would like to know whether I should/need to allow ICMP  
> through as well as udp 123 for NTP to work properly.

You should be letting icmp unreachables in anyway - it's required for 
proper network connectivity.  By all means block echo request packets 
(although I personally never saw the point of that) but let the rest 
through.

That's looks like it's just a misconfigured client not allowing your NTP 
reply packets through - it happens... not that unusual.

Tony


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