First, I would suggest creating a separate VLAN and change the management VLAN of this switch. This will prevent you from being able to manage the switch from any system on the network, but is the recommended configuration for medium to large networks. You can configure a workstation or server on the same VLAN and use it as a management station. To be consistant, you may want to use the same management VLAN on all of your managed switches.

The next step would be to capture traffic and establish a baseline. Determine what percentage of broadcast/multicast traffic is running across the network. A broadcast percentage above 20% is excessive. If you have 50% or above, you really need to look into segmentation.

Also, the Cisco equipment is most likely using proprietary protocols like PVST and CDP/VTP (unless they have been disabled). Look for these protocols in your packet capture. If you see them, you should filter them from the switch. Multicast filtering is a new feature in the latest firmware and is only available via the CLI.

To filter PVST, use the command "mcast mac-addr filter 01-00-0C-CC-CC-CD" from global configuration mode.

To filter CDP/VTP, use the command "mcast mac-addr filter 01-00-0C-CC-CC-CC" from global configuration mode.

Greg,

We are in the process of doing exactly that, but I did not meet with great success when I tried to set up an 802.1q trunk between the Cisco and the Dell switches.  As a result, I had to install the Dell with the default VLAN.  I haven't had a chance to try this with the V2.1 firmware yet.

You mention filtering protocols on the switch, is this documented anywhere?  I didn't find anything on the CD that comes with the switch.  Thanks for your help!

--Roland W. Fox

The multicast filter is a new feature of the 2.1.0.0 firmware. Currently, it is only available through the CLI at this time and its use is not documented in any of the addendums. We will be working on documenting the feature and again listing the MAC addresses for PVST and CDP/VTP in the Dell Knowledge Base.

Per other posts in other threads, we have meet with great success in keeping our PC 3248s alive by:

a) Moving the Cisco management IP address into a different VLAN,

b) Installing Firmware V2.1.0.0 on the PowerConnect 3248s, and

c) Disabling IGMP on the PowerConnect switches.

Since we have done this four months ago, we have not had a PC3248 lose managability.

Did you ever try the mcast command?   This is the form of the command that worked for us:

mcast mac-addr filter 01-00-0c-cc-cc-cc vlan 1
mcast mac-addr filter 01-00-0c-cc-cc-cd vlan 1

When we put these commands in our configuration it helped reduce the lost management issue.