Cisco 3650-48PS Uplink Issue > Nexus 5548UP

[stevenle]

Trying to get a trunk uplink between a Cisco 3650 to a Nexus 5548UP up and running. It's turned into the most complicated issue ever. GBIC and fiber cable have been proven good by connecting the 3650 to a 3560 using the same equipment and configuration.

The 3650 is running Version 03.06.04.E. Using a GLC-SX-MM gbic with MM fiber. Switches are in the same rack. Configuration on the 3650 port is below.

interface GigabitEthernet1/1/1
description Uplink to 5KA
switchport trunk native vlan 7
switchport mode trunk

As soon as I plug the fiber into the Nexus switch I get the output below on the 3650

%PM-4-ERR_DISABLE: link-flap error detected on Gi1/1/3, putting Gi1/1/3 in err-disable state

The Nexus is a N5K-C5548UP version 5.2(1)N1(4. Using same GLC-SX-MM gbic with fiber. Configuration is below.

version 5.2(1)N1(4)

interface Ethernet1/31
switchport mode trunk
switchport trunk native vlan 7
spanning-tree port type normal
speed 1000

I proved out the physical layer by connecting the 3650 to another switch and it comes up right away. I verified that the transmit on the fiber strand on one end is going to the receive on the other end (light to no light). I messed with the spanning tree port type, speed non negotiate settings as well. 

A 10 minute item has now dragged on for two days and it's killing me. Configuration for the 3650 is attached. I have plenty of other model Cisco switches connected to my 5K's. I can connect this 3650 to a production 3560 but I cannot connect a 3650 to a Nexus 5548. I'm at wits end here. 

Let me know if anyone has had this issue or if I am overlooking some small item. Thanks.

[stevenle]

All my access switches have the STP values modified. This was done by the prior administrator. I am planning to remove all these but am first working in replacing all the switches in the access layer with 3650's. If I can get these to work, no luck so far.

I removed the STP modified values but it made no difference. Still get err-disable immediately. Thanks for the suggestion though.

[ahmedshoaib]

Hi;

Please configure the "speed 1000" on Nexus 5K side where you connect the SFP GLC-SX-MM and shut & no shut the interface.

Thanks.

[stevenle]

The configuration is set for speed 1000 on the nexus side. Interface has been shut / no shut. Still no connectivity.

[chrihussey]

Got a 5548s connected to a bunch of 3560s with trunks. Don't have the "spanning-tree port type normal" in the Nexus interface configuration. They are running different versions too. 7.1(1) & 5.2(1).

[stevenle]

**FIXED**. So if you have a Cisco C3650-48PS-L running Version 03.06.04.E of IOS you will be unable to connect to a Nexus 5548UP running 5.2(1)N1(4) with a GBIC and fiber. I worked with TAC for hours to troubleshoot and finally upgraded the IOS to 3.06.05.E and the issue rectified immediately with no further configuration.

They pointed me to Cisco Bug: CSCuz43095 which doesn't make much sense and the workaround doesn't work. Strangest issue I've run across but hopefully this will help others as it's an easy fix. I thought to upgrade pretty quickly but I was on the recommended version of IOS software per Cisco's site. Although they just changed it. Unfortunate that this took so much time. Thanks very much to all those who helped.

Bug Search Bug Search - Cisco Systems

Symptom:
When the C3850 or C3650 is running 03.06.04E, an interface doesn't come up, though the SFP is detected.

Conditions:
When the C3650 is running 03.06.04E.

Workaround:
Moving to another port helps.