Vlan flapping between ports

[diegosaav]

Hi all,

I have the following physical topology:

Router Cisco 2851 <-----> some huawei and raisecom switches <-----> Switch Cisco  WS-C2960-24TT-L <------> Ubnt in AP mode

In C2960 there are a lot of warnings regarding to mac flapping:

Jul 15 18:11:51.626: %SW_MATM-4-MACFLAP_NOTIF: Host 001b.5443.f6dx in vlan 101 is flapping between port Fa0/6 and port Fa0/20

Port Fa0/6 goes to Ubnt Wireless AP and Port F0/20 goes to Cisco 2851.

001b.5443.f6dx is the default gateway for Ubnt's MGMT and C2960 is trying to learn that MAC address from F0/6, which is a strange behavior

Many thx for your time,

-d

[Rajeev Sharma]

Hey,

This mac flap notification says switch is seeing host 001b.5443.f6dx on these two ports. Is there any connection between Ubnt and huawei and raisecom switches?

HTH.

Regards,

RS.

[diegosaav]

Hi rajeevsh,

I was investigating further and I found that a couple of switches along the path have not configured STP, as follows:

Huawei Swtich

dis stp brief 
 MSTID  Port                        Role  STP State     Protection
   0    Ethernet0/0/1               DESI  FORWARDING      NONE
   0    Ethernet0/0/2               DESI  FORWARDING      NONE
   0    Ethernet0/0/3               DESI  FORWARDING      NONE
   0    Ethernet0/0/4               DESI  FORWARDING      NONE
   0    Ethernet0/0/6               DESI  FORWARDING      NONE
   0    Ethernet0/0/7               DESI  FORWARDING      NONE
   0    Ethernet0/0/8               DESI  FORWARDING      NONE
   0    Ethernet0/0/24              DESI  FORWARDING      NONE

Raisecom Switch

sh spanning-tree detail 
MSTP Admin State: Disable
Protocol Mode: MSTP

Would it be possible that these misconfigurations being causing mac flapping?

Thx,

-d

[Rajeev Sharma]

Hey,

Its best to draw a layer 2 topology and check how it is connected. Its a high possibility that we are seeing syslog due this switch as when STP is disabled switch starts acting like hub.

HTH.

Regards,

RS.