Cisco ASA 5505 Outisde Interface MAC?

Posted on 2011-05-09
Last Modified: 2012-05-11
I'm going to be installing three Cisco ASA 5505's, the ISP is assigning a static IP to the device via a DHCP reservation.  So they are naturally requesting the MAC address of the three devices.

I used the command "show int outside" to get the MAC and thought I was all set.  I tried setting up a reservation for one of the devices on my network just to make sure all was well.

Show int outside returns the MAC of: 6400.f16e.1084
However when I look at the DHCP table on my server it says the device MAC is:


What gives?  How can I get the proper MAC to provide to my ISP?

BTW my DHCP reservation for 6400.f16e.1084 was ignored.

Thanks in Advance.

Question by:Railroad
    LVL 33

    Expert Comment

    The "show int outside" does reflect the hardware MAC of the interface, showing the 12 hex character MAC address along with MTU.    I have no idea what that long number represents.

    If you put a switch in front of the ASA, and list MAC addresses on the switch, does it show up correctly?  

    LVL 18

    Expert Comment

    On the 5505, interfaces are assigned to VLANs.  The interface name is associated with the VLAN, not the physical address of the Ethernet interface.  I suspect the MAC you saw was for the virtual interface, not the physical one.  Do "show interface Ethernet0/0" and see how that compares.

    Can't explain the long address from your server.  That seems odd.

    Author Comment

    @MikeKane  What is the command to see MAC's on the switch?  It's a 2960.

    @jmeggers  Yes the MAC for E0/0 is different, added a reservation for that MAC and it was ignored too.

    Accepted Solution

    I figured it out needed to add the command:

    dhcp-client client-id interface outside

    That reports the proper MAC to the DHCP server.

    Author Closing Comment

    Proper solution

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