MAC Address and Logical Router Interface

Well, why don't you configure it and have a look? I suppose you are asking a theoretical question?

Usually it will not matter of they are the same. The different VLANs do not usually end up being connected so no conflict occurs.

It is of course possible that some requirement might result in the vlans being connected by a cable somewhere in the network. This could result in communication failures.

One related thing is that by default Sun workstations use the same MAC address for all of the interfaces in the device. This usually works OK since the different interfaces are not usually in the same broadcast domain.

On 06 Nov 2008 bod43 wrote in news:f62a24b7- snipped-for-privacy@a3g2000prm.googlegroups.com:

Because I don't have any CISCO kit available at the moment. I take it from the rest of your answer the short answer is Yes.

Yes. I have a piece of equipment that has 2 physical ports with addresses in different subnets. They share a MAC but any broadcast traffic (STP, ARP etc) are always sent out of both ports. I'm trying to find out how other equipment handles having 2 IP with 1 MAC handle this, only thing I could think of was logical interfaces.

Thanks.

it depends :)

the hardware can support different MAC addresses on the same interface (at least since the 25xx routers).

this used to be common - DECnet forced the MAC address to include the L3 address, XNS forced all ports to the same MAC and so on.

Different MACs are used with HSRP / VRRP by the current "owner" of a shared gateway address, for different groups and for the native address.

i think if you have multiple IP addresses on a port, it will use the same MAC - but it is so long since i tried i dont remember.

on cisco switches each vlan interfaces gets a separate MAC, so you will different MACs per IP interface in each VLAN on a trunked interface.