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Community Member

Duplicate Mac Address - Partial request time out

Hi

We are currently facing a weird situation. We installed a new cisco switch 2960 lets call it Switch_floor_2 as in the below diagram

Core_switch --> Switch_floor_1--> Switch_floor_2

After the installation we were unable to telnet to the switch using its management IP. Precisely out of 10 Icmp Echo Requests we are getting only 1-2 replies.

The weird thing is that the Core_switch is learning the mac-address of the management IP of Switch_floor_2 from 2 vlans.

The one is the management vlan (Vlan 500) and the other is the vlan we are using for our Riverbed devices (VLAN 700).

In Switch_floor_2 there is nothing connected except the trunk link with Switch_floor_1.

Core_switch#show mac-address-table | include a8c1
*  700  xxxx.xxxx.a8c1   dynamic  Yes          0   Fa3/11
*  500  xxxx.xxxx.a8c1   dynamic  Yes          0   Gi4/5

(xxxx.xxxx.a8c1 is the mac-address of management interface vlan in Switch_floor_2 )

Is there a possibility of a duplicate mac-address in our network?

5 REPLIES
Hall of Fame Super Blue

Re: Duplicate Mac Address - Partial request time out

akisbouza wrote:

Hi

We are currently facing a weird situation. We installed a new cisco switch 2960 lets call it Switch_floor_2 as in the below diagram

Core_switch --> Switch_floor_1--> Switch_floor_2

After the installation we were unable to telnet to the switch using its management IP. Precisely out of 10 Icmp Echo Requests we are getting only 1-2 replies.

The weird thing is that the Core_switch is learning the mac-address of the management IP of Switch_floor_2 from 2 vlans.

The one is the management vlan (Vlan 500) and the other is the vlan we are using for our Riverbed devices (VLAN 700).

In Switch_floor_2 there is nothing connected except the trunk link with Switch_floor_1.

Core_switch#show mac-address-table | include a8c1
*  700  xxxx.xxxx.a8c1   dynamic  Yes          0   Fa3/11
*  500  xxxx.xxxx.a8c1   dynamic  Yes          0   Gi4/5

(xxxx.xxxx.a8c1 is the mac-address of management interface vlan in Switch_floor_2 )

Is there a possibility of a duplicate mac-address in our network?

What are fa3/11 and gi4/5 connected to ?

Jon

Community Member

Re: Duplicate Mac Address - Partial request time out

Jon thanks for answering.

Port Gi4/5 is the one connecting Core_Switch with Switch_floor_1

Port Fa3/11 is the Riverbed_Wan port between our two sites.

I suppose the Riverbed is working like this

                                Site 1                                                                   Site 2

Core_Switch (Fa3/11) --> Riverbed_Interface_Site1  --> Riverbed_Interface_Site2 --> Core_Switch_Site_2

Akis

Hall of Fame Super Blue

Re: Duplicate Mac Address - Partial request time out

What do the arp tables show on the core switches for that mac-address.

Also do you need vlan 700 on the trunk links from the core switch to switch_floor_1 to switch_floor_2. If not it may be an idea to remove that vlan from the trunk links.

Jon

Community Member

Re: Duplicate Mac Address - Partial request time out

Core_Switch#show arp  | include x.x.x.104

Internet  x.x.x.104          30   xxxx.xxxx.a8c1  ARPA   Vlan500

The arp table in the Core_Switch seems to be fine.

I have already tried removing vlan 700 from all trunk links but no result,

The intermediate switch_floor_1 is a WS-C2924M-XL and had 1 module  WS-X2931-XL. Since i installed the second module WS-X2931-XL in order to connect it with the switch_floor_2 i havent done a reset in the switch_floor_1.

Maybe i ll try a reload and will let you know.

Thanks

Community Member

Re: Duplicate Mac Address - Partial request time out

The reload of the intermediate switch fixed the problem.

So when installing WS-X2931-XL modules in a  WS-C2924M-XL always reload as weird things happen..

Jon thanks a lot

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