5500 / 3548 vlan and mac addr. Q

[slazzari]

Ok, here is the background. Not sure of the answer to this one, can anyone help? TIA!

- Older Sun workstations derive their ethernet I/F address ("MAC address&quot from values stored in the system PROM, rather than from values in PROM/ROM on the Ethernet cards themselves. As a result, when multiple I/Fs are present on (older) Sun system, they all have the same MAC address.

QUESTION:

We have an older (Sparc20) NIS server with 3 or 4 I/Fs in it, each of which is on a different VLAN; they all have the same Ethernet address, so:

How do the layer 2 switches cope with this, without disabling some ports? Is it because the multiple I/Fs are plugged into different switches (or ports on a switch), and the source frames that it sees (from the same MAC address, but different VLANS) are "tagged" by VLAN on the trunk, and that OSPF works only on a VLAN-by-VLAN basis, or maybe the trunks are not subject to OSPF?

 

[Fsebera]

Wow, it sounds like you've got a mess (sorry).
If you connect the same MAC address on multiple ports, the switch will send frames destin for that MAC address to ALL of the ports with that MAC address --
IE 00-c0-4f-34-ff-3e on ports 1/2,1/4,1/7,3/2

Anytime device "H" wants to communicate with your sparc20, MAC address 00-c0-4f-34-ff-3e, and you have multiple connections to the switch (ports 1/2,1/4,1/7,3/2) the switch will send frames from device "H" to all the ports with MAC ADDRESS 00-c0-4f-34-ff-3e, UNLESS each port is in a different vlan, then it becomes a bigger problem. To really confuse things, now your Sparc station becomes a router too - not good 'cause a sparc20 is already VERY slow.
Frank