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New Member

Unable to ping multicast NLB across switches ??

Hi, firstly I am still very new to Cisco switches so please bear with me.....

I have two servers here and have setup multicast Network Load Balancing which has worked fine.

Server 1 -

Server 2 -

Virtual IP Adress -

These ares are on our main Cisco 3750 stack and any server connect to this switch can ping all three IP address.

Now on the edge switches we use 2960's. Any servers / laptops / workstations cano not ping the virtual IP Address. They can ping the teo physical ones.

Reading around I need to add the MAC address to the ARP table or something ?? However I have no idea what that means and what to do ?

Any pointers please,


Hall of Fame Super Silver

Re: Unable to ping multicast NLB across switches ??

Hello Will,

see this link

you need to add an ARP entry if you want to ping from the C2960 switches, in order to make the users connected to the C2960 to be able to ping the virtual IP address  you need to define a static CAM  for the multicast MAC address entry that uses the uplink port towards C3750 stack

The reason is that LAN switches do not learn these multicast MAC addresses as it happens for standard unicast MAC addresses

>>>However, since the incoming packets have a  unicast destination IP       address and multicast destination MAC the Cisco device ignores this  entry and       process-switches each cluster-bound packets. In order to avoid this  process       switching, insert a static mac-address-table entry as given below in  order to       switch cluster-bound packets in hardware.

mac-address-table static 0300.5e11.1111 vlan 200 interface

Also use a multicast MAC address that is out of the multicast MAC addresses used to map IPV4 multicast addresses in order to avoid issues with IGMP snooping. The one in the example is fine.

Hope to help