Cisco6509

We had a couple 6509 and also notice that it was alway the 1 packet loss.  We did talk to the Cisco tech support a while back and was told it was a know issue with the software code.  It was not a problem and issue with the hardware or layer 1 issue.  We got use to ignore the 1 packete loss.
One the new Sup engine we haven't have the problem.

If you ping it again within a reasonable time, does it still drop the first packet or do you get all 5 replies? It usually has to do with switch building its MAC and arp tables and not replying to ping until it's all done. I've seen this on a lot of cisco switches over the years and I don't even think about it.

When you ping from a router,  it is expected for the 1st packet to drop, this is normal under circumstances and does not usually represent a problem -- the device you are pinging may not be in the arp table.    The ping can be lost while the arp query is going out to find the MAC address of the device you are pinging.

Try running the ping multiple times.   Try using a higher repeat count, e.g.
ping ip 10.43.16.66  repeat 20 timeout 3

See if the issue does not appear until no activity for 5 minutes or so.


Occasionally routers will also drop packets/fail to respond to a percentage of ping packets if their CPU is busy,  because other processes such as forwarding production traffic and management functions are higher priority for a router than processing and responding to ping requests to the router itself.


When that happens it represents heavy load on the router, but not necessarily any kind of problem.


To test network performance ping between hosts,  or  use other tools that test connectivity between hosts, not routers.

Pinging a router is only a test of basic connectivity,  not a reliable network performance,  link quality, or loss test