VLan & MAC

RouterOS General
1

Hi,
How can i create different Virtual Interfaces with different MAC-Addresses on the same Ethernet Interface?

If no, can this feature to be added in the new releases?

Thanks a lot

2

Yes, you can create different VLAN interfaces with different VLAN-ID (tag) on the same interface, MAC-address should be taken from parent Ethernet interface.

3

I want to set a different MAC address for each VLAN.
How can i do it?

4

not possible.

5

Can it be done in the new releases?

6

that would require the interface to run in promiscous mode which in itself has different problems and might require special handling in each interface driver. Although the upper layers in the network stack should handle most of the issues you might consider that an interface in promiscous mode would pass all packets up to the next layers instead of just packets destined for that specific interface mac resulting in a very high packet processing load on a router connected to a hub (or a switch) as the system would need to process all packets coming in on an interface regardless of whether it’s relevant or not. Irrelevant packets are normally filtered out by the NIC chipset and would not require anything from the upper system.

To maintain that same level of efficiency a nic must be able to support multiple mac addresses and these must not be specifically set for multicast/manycast packets. So of the about 20 chipset that i know today only about 5 of them can do this since many limit the mac address list to multicast only, since it’s only consulted when receiving a packet with the multicast/manycast bit set, and general to them all is that a list of possibly 20 or so (some support fewer, some support more) entries in the programmable mac address list.

If the feature does come it comes with a price of much lower efficiency or the price of only a handful of chipsets supported.

Perhaps it is, in some cases, better to add more bridges to the switch instead? cisco switches default to sharing one bridge regardless of the number of vlans, unless you specifically tell it to use more bridges.