MAC Address and Logical Router Interface
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Posted by Graham Drabble on November 5, 2008, 5:59 pm
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Do all the logical interfaces on a physical Ether interface have the same MAC address? If not how is the MAC address for eahc logical interface defined? Thanks, -- Graham Drabble http://www.drabble.me.uk/ | |||||||||||||
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Posted by bod43 on November 5, 2008, 9:21 pm
Please log in for more thread options  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. | |||||||||||||
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Posted by Graham Drabble on November 6, 2008, 12:26 am
Please log in for more thread options 3517-4f71-b24c-a86290484222@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. -- Graham Drabble http://www.drabble.me.uk/ | |||||||||||||
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Posted by Stephen on November 7, 2008, 4:07 pm
Please log in for more thread options On Wed, 05 Nov 2008 22:59:35 GMT, Graham Drabbleit 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. -- Regards stephen_hope@xyzworld.com - replace xyz with ntl | |||||||||||||
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> Do all the logical interfaces on a physical Ether interface have the
> same MAC address? If not how is the MAC address for eahc logical
> interface defined?