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Beginner

MAC address not being learnt on two switch ports

Hi All,

 

A dell 240 server is connected on two different switch ports with proper vlan configurations on the switch end. 

The server vendor claims to have put a static ip address without gateway on both these ports and the ip's do match the subnet range of the vlans under which the ports are access ports. The interface is showing physically up on the Cisco 3750 switch, but ARP is not being learnt.

 

Another server with the same port level configuration on the same Cisco 3750 switch is working fine. 

 

As a test i disconnected the server from the switch totally and connected a laptop directly to the ports on the server and configured the ip address of the laptop to be in the range of the static ip address of the server and default gateway was set to server ports static ip address. Tried a direct ping to the static ip but get request timed out. Had initiated a Wireshark capture during the ping and observed that the server is not responding to ARP request itself.  I am not able to understand why the server is behaving so. 

 

Unfortunately, i do not have access to the server to confirm if the static ip address is indeed set ? But the vendor tells me the default gateway is not set. The working server ports too do not have the default gateway not set on them but it works fine. 

 

The switch-ports that connect to the server are trunk ports. Unable to understand the reason for such behavior. 

 

Any suggestions please.. 

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VIP Advocate

Re: MAC address not being learnt on two switch ports

Hi,

As you don't have server access and the server is not responding to the ARP packet means something is the wrong configuration on the server-side. Can you test a few things:

1. Is your Switch learning the server mac address? If not then try to adjust the VLAN ID in tag or untag. Check for mac-address learning.

2. Is Server NIC configured with VLAN ID? If then configure a trunk port on the switch and make tagged the same VLAN on the Switchport and try to ping.

3. Is server Having any type of firewall enabled? 

4. Is Server configured with any type of Virtual Switch as VMware or Hyper-V? If yes, then check your Vswitch configuration.

 

 

 

 

Regards,
Deepak Kumar,
Don't forget to vote and accept the solution If this comment will make help you!

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6 REPLIES 6
VIP Expert

Re: MAC address not being learnt on two switch ports

Hi,

Why is the port configured as trunk? Does the server have multiple IPs in different vlans if not, the port should be an access port.

HTH

Beginner

Re: MAC address not being learnt on two switch ports

The server LAN port is trunk as it needs to carry two vlans hence the trunk on switch side , while the WAN port is access port for a single vlan. The working server on the same switch has exactly same port level configuration.  The only fact to check is the settings at the server level which is not even responding to pings when the laptop is connected to the IDRAC port of the server. The pc was made part of the same subnet as that of server and interface was fine. The idrac mac address was statically added to the laptop arp table to see if there would be any difference but none...

VIP Advocate

Re: MAC address not being learnt on two switch ports

Hi,

As you don't have server access and the server is not responding to the ARP packet means something is the wrong configuration on the server-side. Can you test a few things:

1. Is your Switch learning the server mac address? If not then try to adjust the VLAN ID in tag or untag. Check for mac-address learning.

2. Is Server NIC configured with VLAN ID? If then configure a trunk port on the switch and make tagged the same VLAN on the Switchport and try to ping.

3. Is server Having any type of firewall enabled? 

4. Is Server configured with any type of Virtual Switch as VMware or Hyper-V? If yes, then check your Vswitch configuration.

 

 

 

 

Regards,
Deepak Kumar,
Don't forget to vote and accept the solution If this comment will make help you!

View solution in original post

Beginner

Re: MAC address not being learnt on two switch ports

Hi Deepak,

 

Thanks for the suggestions, Point 1 is checked but the other points on server side is not checked as the server is inaccessible from any of its management ports idrac, console etc... Anyway have reached out to the server vendor for tech to come in to check settings from server perspective. Thanks 

Beginner

Re: MAC address not being learnt on two switch ports

Hi 

 

Did you check the native vlan configuration in both ends? Maybe, you have a vlan mismatch. Also, check the spanning tree state on the ports. 

 

could you shared with us the following commands?

 

Show interface trunk, show interface gix/x switchport, show spanning-tree int gix/x

sh

 

Beginner

Re: MAC address not being learnt on two switch ports

Hi Andre, 

 

That has been checked to fine at the switch end and seemingly the issue is on the server. Nevertheless thanks for your comments.

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