10G etherchannel between 4510 and 3850 - NO Link

[tkruggel11]

I'm pulling my hair out on a simple issue, and I could use some advice.   Thank you, in advance.

I've got a core 4510 switch with 2 12-port 10GE SFP+ modules and my closet has a stack of 3 3850-48p with 2 4-port C3850-NM-2-10G  modules.

I'm using 4 SFP-10Gb-SR SFP's to create an ether-channel between these two switches.  

The fiber between them is OM4 cable, and OM3 patch cables.

The distance is about 90 Meters.

I've got po8 created on the 4510 through te1/8 and te2/8.  On the 3850, i've got po8 created on te1/1/4 and te3/1/4.  My problem is that I cannot get a link light at all between these ports.  Absolutely nothing indicating when i hook it up.  I've tested all the patch cables using loop backs and they all respond.  I can even loop back through the complete length of the fiber and i get a link light then also. When i hook them up together, the log on the 4510 starts throwing Rx power low alarms with an Operating value of -29.5 dBm.

I've had Cisco's support go through and verify my port-channel configuration, and they found it to be correct.  

I'm starting to wonder if there is larger forces at work here.  Am i bumping into a compatibility issue?

Any help would be appreciated.

[Reza Sharifi · Accepted solution]

Have you tried crossing the strands on one side of the link and see anything comes up?

Can you try connecting a single port between the 2 switches without any port-channel?

for example port 1/8 to 1/1/4

he log on the 4510 starts throwing Rx power low alarms with an Operating value of -29.5 dBm.

That is a cosmetic bug according to Cisco and happens when ports have optics in them without any fiber patch cords.

HTH

[tkruggel11]

I've removed the interfaces from the etherchannel and tried cross looping.  On the 4510 I get no indication from the LEDs.  On the 3850 I get immediate indication on the LEDs.

One might conclude, Cisco support included, that the SFPs on the 4510 side were bad and should be replaced.   I hesitate to conclude this because, while members of the etherchannel, i get link lights when looping immediately.  Its only when setting the 4510 interfaces back to default and outside the etherchannel that i don't get a response.

[Reza Sharifi]

Do you have the correct sup in the 4500?

see table-2 in this link:

http://www.cisco.com/c/en/us/products/collateral/interfaces-modules/catalyst-4500-series-line-cards/product_data_sheet0900aecd802109ea.html

SFPs hardly ever go bad.

Are these Cisco SFPs? 

HTH

[tkruggel11]

Yes it is the correct sup, and yes they are Cisco optics.  SFP-10Gb-SR to be exact. 

I don't have any other 10Gb etherchannels in use, but i do have several 1Gb channels configured.  I have four other individual 10Gb links, but i'm using 10Gb-LR and 10Gb-ER in those.

I thought i might be coming up against a distance spec initially, but the SRs say up to 400 meters using om4 fiber.

[tkruggel11]

This is great advice and it took a while, but i eventually came back to it.  In the process, I discovered that I've got on bad SFP so support replaced it.  But that wasn't the problem.  

The patch cable was crossed from the factory.  I disassembled the end of the patch cable and individually placed the strands in the optics.  Immediate link light. 

Thank you for the advice.

T