HOST Flapping issue on WS-C2960L-8TS-LL

[#1]

Dear Team,

This is regarding to Host flapping issue due to Cisco 8 or 16 ports switch. We have tried to change Switch IOS to test the flapping issue, After changing the IOS, error was not resolved. We are still issue of host flapping when we connect these 8 port switches to our network. Kindly advise how to resolve the issue. 

Following was the IOS we tried:

Model:  WS-C2960L-8TS-LL

IOS:     flash:c2960l-universalk9-mz.152-5.E.bin

Following is the original IOS of Switch(8 ports)

Model:  WS-C2960L-8TS-LL

flash:c2960l-universalk9-mz.152-5c.E/c2960l-universalk9-mz.152-5c.E.bin

As soon as we connect the switch in our network, we got the following error.

May  8 2017 10:38:19 PAK: %C4K_EBM-4-HOSTFLAPPING: STANDBY:Host 90:B1:1C:A7:08:89 in vlan 26 is moving from port Po2 to port Po4

May  8 2017 10:38:19 PAK: %C4K_EBM-4-HOSTFLAPPING: STANDBY:Host 90:B1:1C:A7:08:89 in vlan 26 is moving from port Po4 to port Po2

May  8 2017 10:39:46 PAK: %C4K_EBM-4-HOSTFLAPPING: Host 98:90:96:9C:0F:C5 in vlan 32 is moving from port Po3 to port Po4

May  8 2017 10:39:46 PAK: %C4K_EBM-4-HOSTFLAPPING: Host 98:90:96:9C:0F:C5 in vlan 32 is moving from port Po4 to port Po3

May  8 2017 10:39:46 PAK: %C4K_EBM-4-HOSTFLAPPING: STANDBY:Host 98:90:96:9C:0F:C5 in vlan 32 is moving from port Po3 to port Po4

May  8 2017 10:39:46 PAK: %C4K_EBM-4-HOSTFLAPPING: STANDBY:Host 98:90:96:9C:0F:C5 in vlan 32 is moving from port Po4 to port Po3

May  8 2017 10:43:50 PAK: %C4K_EBM-4-HOSTFLAPPING: Host 64:00:6A:49:49:56 in vlan 60 is moving from port Po7 to port Po4

May  8 2017 10:43:50 PAK: %C4K_EBM-4-HOSTFLAPPING: STANDBY:Host 64:00:6A:49:49:56 in vlan 60 is moving from port Po7 to port Po4

May  8 2017 10:43:54 PAK: %C4K_EBM-4-HOSTFLAPPING: Host 64:00:6A:49:49:56 in vlan 60 is moving from port Po4 to port Po7

May  8 2017 10:43:54 PAK: %C4K_EBM-4-HOSTFLAPPING: STANDBY:Host 64:00:6A:49:49:56 in vlan 60 is moving from port Po4 to port Po7

May  8 2017 10:45:37 PAK: %C4K_EBM-4-HOSTFLAPPING: Host 38:60:77:12:CD:99 in vlan 60 is moving from port Po1 to port Po4

May  8 2017 10:45:38 PAK: %C4K_EBM-4-HOSTFLAPPING: Host 38:60:77:12:CD:99 in vlan 60 is moving from port Po4 to port Po1

May  8 2017 10:45:37 PAK: %C4K_EBM-4-HOSTFLAPPING: STANDBY:Host 38:60:77:12:CD:99 in vlan 60 is moving from port Po1 to port Po4

May  8 2017 10:45:38 PAK: %C4K_EBM-4-HOSTFLAPPING: STANDBY:Host 38:60:77:12:CD:99 in vlan 60 is moving from port Po4 to port Po1

May  8 2017 10:54:33 PAK: %C4K_EBM-4-HOSTFLAPPING: Host F8:B1:56:E1:3D:B2 in vlan 28 is moving from port Po7 to port Po4

May  8 2017 10:54:33 PAK: %C4K_EBM-4-HOSTFLAPPING: Host F8:B1:56:E1:3D:B2 in vlan 28 is moving from port Po4 to port Po7

May  8 2017 10:54:33 PAK: %C4K_EBM-4-HOSTFLAPPING: STANDBY:Host F8:B1:56:E1:3D:B2 in vlan 28 is moving from port Po7 to port Po4

May  8 2017 10:54:33 PAK: %C4K_EBM-4-HOSTFLAPPING: STANDBY:Host F8:B1:56:E1:3D:B2 in vlan 28 is moving from port Po4 to port Po7

May  8 2017 10:55:13 PAK: %SYS-5-PRIV_AUTH_PASS: Privilege level set to 15 by adminucp on vty0 (172.21.0.18)

May  8 2017 10:55:17 PAK: %C4K_EBM-4-HOSTFLAPPING: Host 34:17:EB:DA:8B:C7 in vlan 28 is moving from port Po7 to port Po4

May  8 2017 10:55:17 PAK: %C4K_EBM-4-HOSTFLAPPING: Host 34:17:EB:DA:8B:C7 in vlan 28 is moving from port Po4 to port Po7

May  8 2017 10:55:17 PAK: %C4K_EBM-4-HOSTFLAPPING: STANDBY:Host 34:17:EB:DA:8B:C7 in vlan 28 is moving from port Po7 to port Po4

May  8 2017 10:55:17 PAK: %C4K_EBM-4-HOSTFLAPPING: STANDBY:Host 34:17:EB:DA:8B:C7 in vlan 28 is moving from port Po4 to port Po7

May  8 2017 10:56:17 PAK: %C4K_EBM-4-HOSTFLAPPING: Host F8:B1:56:E1:3D:B2 in vlan 28 is moving from port Po7 to port Po4

May  8 2017 10:56:17 PAK: %C4K_EBM-4-HOSTFLAPPING: Host F8:B1:56:E1:3D:B2 in vlan 28 is moving from port Po4 to port Po7

May  8 2017 10:56:17 PAK: %C4K_EBM-4-HOSTFLAPPING: STANDBY:Host F8:B1:56:E1:3D:B2 in vlan 28 is moving from port Po7 to port Po4

May  8 2017 10:56:17 PAK: %C4K_EBM-4-HOSTFLAPPING: STANDBY:Host F8:B1:56:E1:3D:B2 in vlan 28 is moving from port Po4 to port Po7

Please let us know if you need any information from us to ascertain the error due to these switches.

Thanks

[Mark Malone]

The issue may not be on that switch but how your setup locally between the switches , what way are you connecting this to the network and whats already in place may be causing this  , is it being dual linked to 2 switches

can you provide any information off the switches your connecting too , is there any alerts being seen there too ?

Troubleshoot

This section lists some common errors that you encounter on the switch, and provides solutions.

Error Message when the Host Address is a Source Address on Multiple Ports

Problem

The %C4K_EBM-4-HOSTFLAPPING:Host [mac-addr] in vlan [dec] is flapping between port [char] and port [char] error message appears.

This error message appears on the switch when the switch detects the specified host address as a source address on multiple ports.

Cause

The issue can occur due to Spanning Tree Protocol (STP) loops in the network that cause packet drops from the specific host. In addition to packet drops, STP loops lead to several other symptoms, which are listed here:

• Loss of connectivity to, from, and through affected network regions.

• High link utilization (often 100 percent).

• High switch backplane utilization (compared to the baseline utilization).

• Syslog messages that indicate packet looping in the network (for example, HSRP duplicate IP address messages).

• Syslog messages that indicate constant address relearning or MAC address flapping messages.

• An increase in the number of output drops on many interfaces.

[#3]

Dear Mark, 

**** Whenever we disconnect these switches from our environment, we DO NOT see any host flapping issue on our switches. Recently we took these switches OFF from our network for more that 24 hours, we did not see any error. As soon we connected these switches, we again got error. ****

We never observe this error on our switches. With the induction of these switches, we start getting this issue.

We have conventional 3-layer network design with Cisco manageable devices. I have explained some detail of our design on phone.

As per your concern of Spanning tree loop, we have re-verified our cabling side. All were ok. Also, there was NO high CPU utilization observed on any switch  & no packet drops. Even with this error, end user does not feel any slowness/disconnections on their system. They(end user) work smoothly and no complaint was registered.

We DO NOT run any FHRP "HSRP" protocol in our whole environment. 

I hope this explain all your query you asked above. However if you need any more information that can help in resolving this issue, please let us know. 

Thanks

[Hitesh Vinzoda]

My assumption:

F8:B1:56:E1:3D:B2 mac belongs to Dell. Do you have any Dell switches in your network?

If you have then try disabling GVRP on the switch.

HTH

Hitesh

[#5]

Dear Hitesh,

As you mention in your earlier email about GVRP, I done some online search, I could not determined that how to disable GVRP on Cisco switches. I guess this command is for NON-CISCO switches. Please correct me if i'm wrong or share how to enable or disable GVRP on Cisco switches.

Thanks.

[Hitesh Vinzoda]

Hi Atif,

I meant to say that GVRP might be enabled on any other non cisco switches, Cisco doesn't recognize these frames and prone to be looping around the network.

I am just pointing that mac address that is appearing in logs belongs to DELL and may be you might have a dell switch in your network.

If above is true, just check the non cisco switches that they have GVRP disabled.

Thanks

Hitesh

[vivek srivastava]

check the native vlan configured in port-channels . It should be same at both ends.

also check as per your design, is vlan28 should be native on trunks ?

[#8]

Dear Vivek,

Native Vlan is already configured on all port-channel. Even if it is NOT configured, a vlan mismatch error will appear on switch log.

Some of our lab users & others are in vlan 28. These are connected through traditional way: Access layer ----> distribution --->core. The access switches are connected to parent switch via trunk.

Following are vlan-28 config.

interface GigabitEthernet1/0/24

 description (B2-CL-203)

 switchport access vlan 28

 switchport mode access

 storm-control broadcast level 20.00

 storm-control action shutdown

 spanning-tree portfast

end

!

interface GigabitEthernet1/1/1

 description *** Uplink from B2-2F-3850-DISTRIBUTION ***

 switchport trunk native vlan  ***************I just hide this native vlan #************

 switchport mode trunk

 switchport nonegotiate

 storm-control broadcast level 20.00

 storm-control action shutdown

Please note that same configuration is on all ports of switch. Please also note that this error is NOT specific to vlan 28. It is with other vlans as well.

Thanks 

[vivek srivastava]

ok, got that.

moving forward, u have given Config for cisco switches. Now can you also check and verify the port-channel Config on these dell switches ?

It is possible that cisco side Config is having port-channel but other end (dell) ports are not joining the port-channel.

[#10]

There is no Dell switch in the whole network. Client has only Dell Systems in this network. 

[vivek srivastava]

So are there two ports on Dell servers connected to different access-switches ?

+

Dell server has one virtual IP against two physical ports ?

[thanhlt4@tpb.com.vn]

Hi!

You can try add "switchport trunk allow vlan on trunk ports"

[thanhlt4@tpb.com.vn]

Hi!

You can try to add "switchport trunk allow vlan on trunk posts"

[rhofer]

We had same issue with two C2960L where the Uplink interface MAC of other access switches was supposedly flapping to the C2960L. We found it to be an issue with IOS version 15.2.(5c)E and could solve it by upgrading to 15.2(7)E7.