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Community Member

Unable to fully form trunks between 3850 and 4503-E switches

Hi all,

This last weekend I tried to replace a stack of 3750G's with a stack of new 3850's.

The stack of switches has 2 fibre uplinks to the core switches (4503-E).

It didn't go well, and I had to revert the project.

The stack was all pre-configured in the workshop but could not be tested  on the live LAN. When I connected it , I first connected up 1 of  the 2 uplinks. The link went to UP status, and I could see the remote core switch via CDP,  but it would not learn the VLANs (VTP was setup correctly), and looking  at the port on the switch, it flashed green, went solid green, then  flashed amber slowly. This cycled continuously, whilst the link status remained up and no errors were logged by either switch.

I debugged spanning-tree but nothing stood out. I tried a replacement SFP, and a different slot but no difference.

I re-connected one of the old 3750's and immediately the link came up stable, and everything was fine.

I then erased the config on the new stack, and simply set the fibre port as  trunk, with udld enabled (matching the remote end) (neither switch  supports ISL, so the trunk is dot1q). The same issue persisted.

Last night I spent a few hours in the office investigating.  I grabbed a spare 3560G from the store, configured a fibre port as a trunk, and connected this to the 3850's, and this worked fine.  I then provisioned a new fibre port on the core 4503-E and connected this up using brand new fibre tails, but had exactly the same issues as described above.

The switches were running cat3k_caa-iosd-universalk9.SPA.150-1.EX3, and I have upgraded them to cat3k_caa-universalk9.SPA.03.03.01.SE.150-1.EZ1.bin as part of my troubleshooting but this has not made a difference.

Does anyone have any advice? I am starting to wish I spec'd 3750X's instead!!

Thanks

5 REPLIES
Green

Unable to fully form trunks between 3850 and 4503-E switches

Tim,

From the 3850 install guide

http://www.cisco.com/c/en/us/td/docs/switches/lan/catalyst3850/hardware/installation/guide/3850_hig/HIGOVERV.html#wp1263129

Table 1-13 NETWORK MODULE LEDs

Color

NETWORK MODULE Link Status

Off

Link is off.

Green

Link is on, no activity.

Blinking green

Activity on a link, no faults.

Note The LED will blink green even if there is very little control traffic.

Blinking amber

Link is off due to a fault or because it has exceeded a limit set in the switch software.


Caution Link faults occur when noncompliant cabling is connected to an SFP or SFP+ port. Use only standard-compliant cabling to connect to Cisco SFP and SFP+ ports. You must remove from the network any cable or device that causes a link fault.

Amber

Link for the SFP or SFP+ has been disabled.

What kind of SFPs are in the 3850

What kind if GBICs are in the 4500

What is the spec of your fibre cable & patches

Regards,
Alex.
Please rate useful posts.

Regards, Alex. Please rate useful posts.
Community Member

Unable to fully form trunks between 3850 and 4503-E switches

Thanks Alex,

I read that from the instal guide, but as it wasn't a constant amber flashing I wasn't sure.  And the fact that the same fibres, and during testing same GBIC, were in use.

Module in the 3850 is GLC-SX-MMD=, but I also tested using a GLC-SX-MM

Module in the 4503 I cannot confirm at the moment, as I am at home.

I will try to establish the spec. of the fibre and patches tomorrow.

Thanks

Tim

Hall of Fame Super Gold

Unable to fully form trunks between 3850 and 4503-E switches

Post the configuration for the physical interfaces and the port channel interfaces of both appliances.

Post the output to the command "sh etherchannel summary".

Community Member

Unable to fully form trunks between 3850 and 4503-E switches

Hi, there is no etherchannel in this configuration.  The stack of 3850's connect to a pair of 4503-E's, which do not have VSS capabailities.

Thanks!

Hall of Fame Super Gold

Unable to fully form trunks between 3850 and 4503-E switches

Sorry.  I misread your posts. 

Post the configuration of the interfaces of both switches.

Post the "sh interface " of both appliacnes.

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