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  1. #1
    Join Date
    Feb 2010
    Location
    San Jose, CA
    Posts
    43

    Default Each interface has its own MAC address??

    So, we all know that a router can have 1 or even up to 8 IP addresses assigned to an interface, but I would like to draw your attention to page 340-341 of CCNA study guide, the answer to the first question says "Lab_B router will respond with the MAC address of the FA0/0 interface" giving the impression that the router has more than one MAC address... so I am confused here, and I done some research online and found a post elsewhere that says "I did an ARP request on network, and the router responded with 3 MAC addresses??"

    So isn't a device supposed to have 1 and only 1 unique HW address??

  2. #2
    Join Date
    Jul 2008
    Posts
    211

    Default

    Just think of each interface as a separate device. That's true of a PC as well; each ethernet interface has its own MAC address.

  3. #3
    Join Date
    Nov 2008
    Location
    Birmingham, UK
    Posts
    1,441

    Default

    Depending on the network topology, a router interface can have multiple MAC addresses. It will only have one physical address per interface, as manufactured, but it can have multiple virtual MAC addresses.

    Have a look at HSRP, VRRP and GLBP (CCNP topics). It will illustrate the idea of virtual MAC addresses and the need for them.

    Another thing to consider is proxy arp. The router might respond to an ARP request for a device that isn't present on the subnet, if the router knows about it, for example, when using one-to-one NAT translation for a remote device.
    CCNP R&S, CCNA DC
    Currently studying: CCIE R&S, CCNP Data Centre
    Follow my CCIE progress with study notes on my blog: http://beyondccna.blogspot.co.uk/

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