[c-nsp] ICMP Packet loss

[Brad Gould]

 > It is strange, I only got packet loss, when I start the
 > ping from the router with a packet size more than the default.
 > I've go no errors on the interface.

That usually means your getting bit errors on your link.

As the packet size increases, its more likely that a single packet will 
get dropped.

Try larger a larger sample with the small packets...

magnum01#ping 1.1.1.1 size 100 repeat 10000

and see if you get any packet loss.

A packet size of larger than the mtu of the interface increases your 
apparent packet loss...

magnum01#ping 1.1.1.1 size 3000 repeat 10000

.... will double the packet loss (usually) because of fragmentation 
(assuming an ethernet mtu of 1500 bytes)

Cheers,

Brad


Ahmad Cheikh-Moussa wrote:
> Hi!
> 
> I have a question to icmp packet loss.
> It is strange, I only got packet loss, when I start the
> ping from the router with a packet size more than the default.
> I've go no errors on the interface. 
> The cpu has a average utilization of 20%.
> The router model: 7206VXR NPE-G1
> 
> Is this normal that the router discard some icmp packets,
> which are destinated to himself and which are bigger than 
> default. Here some debug outputs:
> 
>  magnum01#ping
> Protocol [ip]:
> Target IP address: 1.1.1.1
> Repeat count [5]: 100
> Datagram size [100]:
> Timeout in seconds [2]:
> Extended commands [n]:
> Sweep range of sizes [n]:
> Type escape sequence to abort.
> Sending 100, 100-byte ICMP Echos to 1.1.1.1, timeout is 2 seconds:
> !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
> !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
> Success rate is 100 percent (100/100), round-trip min/avg/max = 1/1/4 ms
> magnum01#
> magnum01#
> magnum01#
> magnum01#
> magnum01#
> magnum01#
> magnum01#ping
> Protocol [ip]:
> Target IP address: 1.1.1.1
> Repeat count [5]: 100
> Datagram size [100]: 300
> Timeout in seconds [2]:
> Extended commands [n]:
> Sweep range of sizes [n]:
> Type escape sequence to abort.
> Sending 100, 300-byte ICMP Echos to 1.1.1.1, timeout is 2 seconds:
> !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
> !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
> Success rate is 100 percent (100/100), round-trip min/avg/max = 1/1/4 ms
> magnum01#ping
> Protocol [ip]:
> Target IP address: 1.1.1.1
> Repeat count [5]: 100
> Datagram size [100]: 600
> Timeout in seconds [2]:
> Extended commands [n]:
> Sweep range of sizes [n]:
> Type escape sequence to abort.
> Sending 100, 600-byte ICMP Echos to 1.1.1.1, timeout is 2 seconds:
> !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!.!!!!!
> !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
> Success rate is 99 percent (99/100), round-trip min/avg/max = 1/1/4 ms
> magnum01#
> magnum01#
> magnum01#ping
> Protocol [ip]:
> Target IP address: 1.1.1.1
> Repeat count [5]: 100
> Datagram size [100]: 1000
> Timeout in seconds [2]:
> Extended commands [n]:
> Sweep range of sizes [n]:
> Type escape sequence to abort.
> Sending 100, 1000-byte ICMP Echos to 1.1.1.1, timeout is 2 seconds:
> !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!.!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
> !!!.!!!!!!!!!!!!!!!!!!!!!!!!!!
> Success rate is 98 percent (98/100), round-trip min/avg/max = 1/1/4 ms
> 
> 
> 
> Any ideas ?
> 
> Thanks in advance,
>  Ahmad
> 
> 
> 
> 
> 
> 

-- 
Brad Gould, Network Engineer
Internode
PO Box 284, Rundle Mall 5000
Level 3, 132 Grenfell Street, Adelaide 5000
P: 08 8228 2999  F: 08 8235 6999
bradley at internode.com.au; http://www.internode.on.net/