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New Member

4 MAC addresses per port limit

For several reason I am using a Fore System 3810 with 1 24 port card (I have to use this piece of equipment!). This card has a limitation of only allowing 4 Mac addresses per port. As of right now I have made a simple gateway program on an SGI that has two interfaces. The SGI is configured with one interface connected to the 3810 (addressed The other interface is connected to a Cisco 3550 (addressed The Cisco 3550 has around 30 machines hooked to it. The SGI takes all the broadcast traffic from the 192.X.X.X net and rebroadcasts it to the 172.X.X.X net. This eliminates my 4 MAC address problem.

I know this is not the best way to do this but it works for now. Does anyone else know a solution I could use? I know that Fore/Marconi makes a card for the 3810 that will do this but I don't want to go that route. Can I use any Cisco equipment to do the same function the SGI does?




Re: 4 MAC addresses per port limit

Hi Blake,

Why do you want the broadcast traffic to be rebroadcasted on the other network?

Would'nt it be sufficient to configure vlans on the 3550, put the 30 hosts in one vlan and the Fore in another vlan, then let the 3550 route between the vlans?

This way you have no extra cost, no extra traffic caused by the re-broadcasting, just a simple routed network. BTW, if you think you need re-broadcasting for DHCP to work, have a look at the "ip helper-address" command.

If the above is not applicable, maybe you could describe your problem in another way?



New Member

Re: 4 MAC addresses per port limit

We run a flight simulation lab that uses a protocol called DIS. This protocol sends out updates in a broadcast form.(Networkers nightmare!) That is the reason I have to allow broadcast traffic.

I did think of using the 3550 as a router between vlans but I couldn't find a way to allow broadcasts. Also right now I am sending all the broadcast on the 192.X.X.X and then using the SGI to rebroadcast it on the 172.X.X.X. When the SGI rebroadcasts the packet it strips the header and gives it a new source of the 172.X.X.X. This makes the packet look like it originated on the SGI. I really like that feature because we connect with new sights every week and that way we don't have to change our internal addressing every time we hook to a new sight.

Now I know this is clear as mud does anyone have an idea?