DHCP Server on an ASA

When configuring the ASA as a DHCP server and then having a router act as a DHCP client I end up with the following show output on the DHCP server (ASA):

IP address                    Hardware address                Lease expiration        Type

  136.8.121.100           0063.6973.636f.2d30.           1760 seconds           Automatic
                                  3031.312e.3231.3234.
                                  2e39.3738.302d.4661.
                                  302f.30

 

What are all the hardware address values?  There is only ine client.  Is it because it has multiple interfaces?  If thats the case, what is 302f.30?  Serial Interface maybe?

 

Thanks


Brandon

Comments

  • What you see if the hex dump of a default DHCP client-ID generated by Cisco IOS router acting as DHCP client. Client-ID is an opaque text string, which may vary with client. For example, Window hosts usually use "hwtype" "hwaddr" strings concatenated in hex. Cisco IOS uses more complicated format, which is as per the following example:



    Client-ID: cisco-0007.ebde.5622-Et0/1
    Client-ID hex dump: 636973636F2D303030372E656264652E353632322D4574302F31

    As you can see, it's the string "cisco-0007.<MAC>-XX/NN" where XX is the short interface name and NN is the interface number. This is the ASCII format for the Client-ID and you can see the hex-dump next to it. This is the value you can see in your bindings command output (under the Hardware Address column).

    The Cliend-ID is used by DHCP servers to index the DHCP bindings database, and provide host-based pools. Note that if a Client-ID field is present in DHCP REQUEST, Cisco IOS DHCP server will ignore hwaddr field, so you can't match a host pool by MAC address, when Client-ID is present. 

    Also you may also force Cisco IOS DHCP client to use any variable client-ID string, or simply base the client ID on hwaddr and hwtype field, like Windows DHCP client does.


  • Thanks Petr!  Makes Perfect Sense.


    On Jul 30, 2008, at 5:01 AM, Petr Lapukhov wrote:

    What you see if the hex dump of a default DHCP client-ID generated by Cisco IOS router acting as DHCP client. Client-ID is an opaque text string, which may vary with client. For example, Window hosts usually use "hwtype" "hwaddr" strings concatenated in hex. Cisco IOS uses more complicated format, which is as per the following example:


    Client-ID: cisco-0007.ebde.5622-Et0/1
    Client-ID hex dump: 636973636F2D303030372E656264652E353632322D4574302F31

    As you can see, it's the string "cisco-0007.<MAC>-XX/NN" where XX is the short interface name and NN is the interface number. This is the ASCII format for the Client-ID and you can see the hex-dump next to it. This is the value you can see in your bindings command output (under the Hardware Address column).

    The Cliend-ID is used by DHCP servers to index the DHCP bindings database, and provide host-based pools. Note that if a Client-ID field is present in DHCP REQUEST, Cisco IOS DHCP server will ignore hwaddr field, so you can't match a host pool by MAC address, when Client-ID is present. 

    Also you may also force Cisco IOS DHCP client to use any variable client-ID string, or simply base the client ID on hwaddr and hwtype field, like Windows DHCP client does.





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