1. Home
  2. Ethernet LAN
  3. MAC address table for each VLAN

MAC address table for each VLAN

Hello,

some L2 switches have separate MAC address tables for VLANs, others don't and share the global one. Then for the latter case packets between two VLANs are forwarded, as long as there are entries in MAC table.

For example:

port1 in VLAN1: station1 with MAC1 port2 in VLAN2: station2 with MAC2

And the table looks as follows:

port1 MAC1 AgeingTime1 port2 MAC2 AgeingTime2

With such configuration any packet from stattion1 towards station2 is forwarded by the switch via port2. Doesn't this break the VLAN concept (i.e. communication between VLANs is possible only via router)?

Please help me to understand this. Thanks !

Reply to
Mark
Loading thread data ...

I'm not sure I understand why the tables you show imply that frames from host 1 would be switched directly to host 2, at layer 2.

The MAC addresses will be aged out, just as they are in any "learning bridge," but the VLAN association is with the switch port, in this case. Not with any one MAC address. For example, any new MAC address appearing at Port 1 will become associated with VLAN 1.

Host 1 should not be able to communicate directly with host 2, unless someone introduces a router with access to both VLANs.

Bert

Reply to
Albert Manfredi

Bonjour Mark,

In your first table MAC1 is a source address, in your second table MAC1 is a destination address. Why don't you have the VLAN information in the forwarding table?

Best regards, Michelot

Reply to
Michelot

Cabling-Design.com Forums website is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.