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Cannot see MAC address to connected port on Switch

Kaushik Ray
Beginner
Beginner

 

Hello

 

I am experiencing a strange problem and would be grateful to have some advice on this.

 

I have a Switch (WS-C3750X-48P-S) version (flash:/c3750e-universalk9-mz.122-55.SE5).

 

I have two devices connected on two ports of the switch Gi1/0/41 and Gi1/0/42.

 

The configuration on the interfaces are as follows:

 

interface GigabitEthernet1/0/41
 description ### ALert Logic monitor port ###
 switchport access vlan 2
 switchport mode access
 load-interval 30
 duplex full
 spanning-tree portfast
end

sw01#sh run int Gi1/0/42
Building configuration...

Current configuration : 196 bytes
!
interface GigabitEthernet1/0/42
 description ### ALert Logic monitor port ###
 switchport access vlan 2
 switchport mode access
 load-interval 30
 duplex full
 spanning-tree portfast
end

But I cannot see them on the MAC address table

sw01#sh mac address-table int Gi1/0/41
          Mac Address Table
-------------------------------------------

Vlan    Mac Address       Type        Ports
----    -----------       --------    -----
sw01#sh mac address-table int Gi1/0/42
          Mac Address Table
-------------------------------------------

Vlan    Mac Address       Type        Ports
----    -----------       --------    -----

I was able to see that a couple of hours back

 

sh mac address-table int Gi1/0/41

          Mac Address Table

-------------------------------------------

 

Vlan    Mac Address       Type        Ports

----    -----------       --------    -----

   2    a036.9f36.d885    DYNAMIC     Gi1/0/41

Total Mac Addresses for this criterion: 1

sw01# sh mac address-table int Gi1/0/42

          Mac Address Table

-------------------------------------------

 

Vlan    Mac Address       Type        Ports

----    -----------       --------    -----

   2    a036.9f36.d884    DYNAMIC     Gi1/0/42

Total Mac Addresses for this criterion: 1

But since I could not see IP addresses getting associated to the MAC addresses, I did a shut / no shut on the port but have not been able to see the MAC address since. Any advice as to what may have gone wrong?

 

sw01(config)#int Gi1/0/41
sw01(config-if)#no shut
sw01(config-if)#int Gi1/0/42
sw01(config-if)#no shut
sw01(config-if)#^Z

 

 

Any hints would be much appreciated.

 

Thanks

 

Kaushik

 

8 Replies 8

Kaushik Ray
Beginner
Beginner

Sorry but anyone seen this problem before?

Hey,

it can happen with NIC teaming, as William said check the virtual mac associated, also the keep-alive intervals under the NIC teaming options.

Regards,
RS

Is it the switch where the node is directly connected ?

Is the NIC at node side, working fine ?

 

Another fact to consider is, a mac will wipe itself out after the MAC-age timeout.

 

--

Parvesh

are those devices are working or idle.may be the mac address table got cleared/expired and there is no traffic initiated or destined to those devices after that.

Regards

Prajith

WILLIAM STEGMAN
Enthusiast
Enthusiast

Are the interfaces currently showing up/up? 

Yes, I think I may have found the problem.

 

I think someone connected two NICs of the same device to the same Switch and VLAN. I think that may be causing this issue?

If they're using NIC teaming, a virtual MAC may have been assigned to the pair of NICs.  You'd need to get a list of any real and virtual MACs from the server admins to nail down the connections. 

ALIAOF_
Frequent Contributor
Frequent Contributor

Are those devices up and their NIC's are not in power save mode?

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