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server two n/w interfaces connecting to switches.

I have 4500 switch configured vlans. i want to connect server which has to two NIC cards. Each NIC card has to connect different switch but same vlan. But we are getting %C4K_EBM-4-HOSTFLAPPING messages frequently. This says between trunk and servert connected ports. Pls suggest solution for this.

3 REPLIES

Re: server two n/w interfaces connecting to switches.

hi sampath,

The error is very strangeforward. You're using 2 NICs connecting on two switches. It's running Active/Active on both NICs. Right? What you can do is as follows:

NIC: Active/Standby

- You can connect two NICs with either 2 switches or one switch.

NIC: Active/Active

- You can connect two NICs with one switch running Etherchannel on the ports. Let's check the server side as well

- You can connect two NICs with two switches that they are c3750-STACK and use Etherchannel fearures.

- You can connect two NICs with one chassis-switch with different line cards and use Etherchannel fearures.

HTH

Toshi

Bronze

Re: server two n/w interfaces connecting to switches.

From the Cisco Error Message Decoder:

%C4K_EBM-4-HOSTFLAPPING: Host [mac-addr] in vlan [dec] is flapping between port [char] and port [char]

The specified host is detected as a source address on multiple ports. Typically, a host is supposed to be learned on only one port. A spanning tree loop is the most common cause of this condition. All traffic from the specified host is temporarily dropped. After 15 seconds, forwarding is reenabled. If the problem persists, the traffic from the problem host continues to be dropped indefinitely.

Recommended Action: Make sure that spanning tree is enabled to prevent spanning tree loops. If you have spanning tree disabled, make sure that you have no spanning tree loops in your network.

You can find more info here:http://www.cisco.com/en/US/products/hw/switches/ps4324/products_tech_note09186a008063c36f.shtml

Community Member

Re: server two n/w interfaces connecting to switches.

check from server side NIC load balancing method.

To resolve this issue configure with Actice/standby mode.

Ganesh.H

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