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Webcast-Catalyst9k
New Member

FEC between 6509 and 7500

I have a pair of two link FECs w/ISL configured from two different 6509s (Sup2/CAT6.1.1b) to the same 7513(12.0(19)). While both seem to be functioning, I am seeing a few disturbing issues.

1) Using an extended ping, I am dropping 6-9% of my packets on these FECs. At the same time, I am running single ISL links from the same two 6509s to a different 7507 (on the same subnet) and not seeing any packet loss.

2) A look at STP on the 6509s show that I am forwarding on both links for all trunked VLANs, but the MAC counters show discards, In-discards on one link, out-discards on the other. The 7513 shows no drops.

3) The port-channel interfaces on the 7513 are setup as full-duplex but a "sh int port-chan" indicates that the port speed is unknown.

I currently have a problem open with TAC, anyone have any ideas? Thanks!!

2 REPLIES
New Member

Re: FEC between 6509 and 7500

Some things I can think of:

-Make sure you're not autonegotiating between the two devices. Fix them both at the same speed and duplex.

-Bias one of your links to be more favored for STP. Only one of the devices will block with STP. You should be able to find it.

-Disable one of the links to see if STP is causing any problem, or if FEC is causing the problem.

Opening a case with TAC is good. You did the next thing I would do!

Let us know what resolves this! Sounds like a good one!

New Member

Re: FEC between 6509 and 7500

Thanks for the input, both ends of the FEC are set to 100/full and STP on the 6509 says that he is forwarding on both links (I can verify this by looking at the MAC counters on the 6509, both ports are going up). I'm pretty sure FEC is the problem, before I implemented FEC I had each leg of the port-channel defined as an individual ISL link between the two boxes and they were working fine. As soon as I introduced FEC my performance went into the bucket. Thanks again...

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