fractional gigabit ethernet links?

Tue Jul 16 15:09:54 UTC 2002

--On Monday, July 15, 2002 10:48 PM -0400 Alex Rubenstein <alex at nac.net> 
wrote:
> I'm trying to troubleshoot a problem with a fractional (311 mbit/second)
> gigabit-ethernet line provided to me by a metro access provider.
> Specifically, it is riding a gig-e port of a 15454.
>
> The behavior we are seeing is an occasional loss of packets, adding up to
> a few percent. When doing a cisco-type ping across the link, we were
> seeing a consistent 3 to 4 percent loss.

I would definitely recommend using something like iperf, instead of ping if 
you want to precisely measure your link performance. Ideally you would have 
two machines on each side of the link to isolate the problem.

Is this link in production? We are using a gigabit ethernet to our 
provider. We are limited on our traffic going to Commodity traffic, but 
have free reign on our Internet 2 traffic. We found that we get the best 
results when we shape/police our traffic to stay within our contractual 
limits, on our side of the link. Since we are using a 6509 with a Sup1A, we 
had to do some tricky things to police traffic on only one vlan of an 
802.1q trunk on the gigE connection. It works though. We see insignificant 
losses on the link.

good luck!

Peter Hill
Network Engineer
Carnegie Mellon University