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Suggestions for accurate speedtest when link is using CEF

nummagumma2 asked
Medium Priority
Last Modified: 2010-03-17
I have a circuit provided by a huge ISP that is 4 T1s bound using CEF (Cisco Express Forwarding).  When using www.speedtest.net this circuit does not show the 6Mbps throughput that we would expect.  Another vendor's circuit using MLPP for 4 bound T1s is showing 6Mbps throughput.

Is there an online test that will show the accurate results for the CEF circuit?

If you know this or can point to information, I'd be appreciate too:
Is there some problem with the way CEF works that would not provide a fully bonded circuit at the higher speed?
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Les MooreSr. Systems Engineer
Top Expert 2008
I would not expect CEF load balanced links to provide anywhere near the 6Mb download speeds you might expect.
The CEF default is to load-balance per connection. No one connection will get more than 1 T1 bandwidth.
You can switch to per-packet on an interface by interface basis, but you still won't get that high download speeds you think.
An MLPPP llink appears to the router as one big fat pipe and acts the same way. With MLPPP you can actually get those higher download speeds, but it is more CPU intensive.

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Top Expert 2006
I pretty much echo what lrmoore said, but think you should be able to get rather close to 6Mbps with per-packet.

But the more important thing here is this: TELL US WHAT RESULTS YOU ARE GETTING!  Are you getting 1.5Mbps?  Are you getting 3Mbps?  Are you getting 149.6kbps?


Duh. =)

The speedtests show something like 3Mbps down and 1.2 up, a far cry from the 6/6 I'd expect.  It looks like a DSL connection, albeit a far more robust solution.

Thanks for the comments so far.
Top Expert 2006

For giggles, can you do two speed tests at the same time, and see if you then get >3Mbps down and >1.2Mbps up?

Getting 3Mbps may indicate that they have per-packet forwarding enabled on their end.


I've been told they are using per-packet forwarding, but I don't know what that means in terms of the overall speed that I'd be getting.  It sounds like you do... is there some reading I can do on this?
Top Expert 2006



Thanks guys.  I learned from speedtest.net that they don't support speed tests on CEF - and that what you both said was true - CEF will show maximum throughput of less than the combined speed due to the way it deals with packets.
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