MAC Flapping on 2960-24TC-L - Netlab POD - Page 2

swillet41 · ‎09-23-2015

Hello,

I am exp MAC Flapping on a 2960-24-TC-L switch between multiple ports (flapping ports move as I shutdown interfaces). The only way to stop the flapping is to shutdown all unused ports.

This is a Netlab POD setup for student labs. The flap does not occur until I use "switchport trunk native vlan 99" on my trunk ports between two switches. If I set the trunk native vlan back to "switchport trunk native vlan 1", the flapping stops. Below is a screenshot of the problem.

Does anyone have a resolution for this? I am not using Etherchannel.

Thanks,

Scott

S1#
!
! Last configuration change at 00:15:19 UTC Mon Mar 1 1993
!
version 15.0
no service pad
service timestamps debug datetime msec
service timestamps log datetime msec
service password-encryption
!
hostname S1
!
boot-start-marker
boot-end-marker
!
enable secret 5 $1$RskD$PbIZIEaed1HdOSL7I2rVj.
!
username admin privilege 15 secret 5 $1$XT2W$PG48x0DN4rdYeNlCUxFRV0
no aaa new-model
system mtu routing 1500
!
!
--More--
*Mar 1 00:15:19.206: %SYS-5-CONFIG_I: Configured from console by console
no ip domain-lookup
ip domain-name ccnasecurity.com
!
!
!
!
!
!
!
!
!
spanning-tree mode pvst
spanning-tree extend system-id
spanning-tree vlan 1 priority 0
!
vlan internal allocation policy ascending
!
ip ssh time-out 90
ip ssh authentication-retries 2
!
!
!
!
!
interface FastEthernet0/1
switchport trunk native vlan 99
switchport mode trunk
!
interface FastEthernet0/2
!
interface FastEthernet0/3
!
interface FastEthernet0/4
!
interface FastEthernet0/5
!
interface FastEthernet0/6
!
interface FastEthernet0/7
!
interface FastEthernet0/8
!
interface FastEthernet0/9
!
interface FastEthernet0/10
!
interface FastEthernet0/11
!
interface FastEthernet0/12
!
interface FastEthernet0/13
!
interface FastEthernet0/14
!
interface FastEthernet0/15
!
interface FastEthernet0/16
!
interface FastEthernet0/17
!
interface FastEthernet0/18
!
interface FastEthernet0/19
!
interface FastEthernet0/20
!
interface FastEthernet0/21
!
interface FastEthernet0/22
!
interface FastEthernet0/23
!
interface FastEthernet0/24
!
interface GigabitEthernet0/1
!
interface GigabitEthernet0/2
!
interface Vlan1
ip address 192.x.x.x 255.255.255.0
!
no ip http server
no ip http secure-server
!
!
line con 0
exec-timeout 120 0
password 7 02050D4808090C2E425E080A16
logging synchronous

login
line vty 0 4
exec-timeout 120 0
privilege level 15
password 7 070C285F4D060F110E020A1F17
login local
transport input ssh
line vty 5 15
login
transport input none
!
end

____________________________________________

S2#sh run
Building configuration...

Current configuration : 1572 bytes
!
! Last configuration change at 00:10:38 UTC Mon Mar 1 1993
!
version 15.0
no service pad
service timestamps debug datetime msec
service timestamps log datetime msec
no service password-encryption
!
hostname S2
!
boot-start-marker
boot-end-marker
!
enable secret 5 $1$2Bh6$IfyNy.dkybQmHGvmLPS/v1
!
no aaa new-model
system mtu routing 1500
!
!
no ip domain-lookup

!
!
!
!
!
!
!
!
spanning-tree mode pvst
spanning-tree extend system-id
!
vlan internal allocation policy ascending
!
!
!
!
!
!
interface FastEthernet0/1
switchport trunk native vlan 99
switchport mode trunk
!
interface FastEthernet0/2
!
interface FastEthernet0/3
!
interface FastEthernet0/4
!
interface FastEthernet0/5
!
interface FastEthernet0/6
!
interface FastEthernet0/7
!
interface FastEthernet0/8
!
interface FastEthernet0/9
!
interface FastEthernet0/10
!
interface FastEthernet0/11
!
interface FastEthernet0/12
!
interface FastEthernet0/13
!
interface FastEthernet0/14
!
interface FastEthernet0/15
!
interface FastEthernet0/16
!
interface FastEthernet0/17
!
interface FastEthernet0/18
!
interface FastEthernet0/19
!
interface FastEthernet0/20
!
interface FastEthernet0/21
!
interface FastEthernet0/22
!
interface FastEthernet0/23
!
interface FastEthernet0/24
!
interface GigabitEthernet0/1
!
interface GigabitEthernet0/2
!
interface Vlan1
ip address 192.x.x.x 255.255.255.0
!
no ip http server
no ip http secure-server
!
!
line con 0
exec-timeout 120 0
password (#@)(($%
logging synchronous
login
line vty 0 4
exec-timeout 120 0
password (#@)(($%
login
line vty 5 15
login
!
end

Ganesh Hariharan · ‎09-23-2015

Hello,

I am exp MAC Flapping on a 2960-24-TC-L switch between multiple ports (flapping ports move as I shutdown interfaces).  The only way to stop the flapping is to shutdown all unused ports. 

This is a Netlab POD setup for student labs.  The flap does not occur until I use "switchport trunk native vlan 99" on my trunk ports between two switches.  If I set the trunk native vlan back to "switchport trunk native vlan 1", the flapping stops.  Below is a screenshot of the problem.  I will post the running config later.

Does anyone have a resolution for this?  I am not using Etherchannel. 


Thanks,

Scott

Hi Scott,

Is the end device netlab POD is having dual connectivity with switches , if yes what type of connectivity and what configuration is been made on these devices.

-GI

swillet41 · ‎09-23-2015

GI,

Yes, both of these lab switches, S1 & S2 have connection to each other and a control switch. See below the shot of the lab connection to the CTRL switch. This lab only uses R1, S1, S2, and 2 PCs which are accessed via the CTRL switch ports because I have a VM Dell server connected to the CTRL switch that is providing VM's -

swillet41 · ‎09-29-2015

Everyone,

This issue is resolved. Because the Netlab is an automated system, we were supposed to use the default config's...instead we were using custom configs. In short, the FA0/2 - 4 ports should have been shutdown on S1/S2 to mitigate a switching loop.

Just wanted to thank everybody for their assistance and input. I am the only Network tech on my team and this is my first Network job, so I really appreciate your feedback. In addition, I did learn a few things about NIC teaming and the affects of redundant switch links.

Thanks,

Scott