CISCO 1721  FastEthernet VS Ethernet0 Configuration Question.

Posted on 2006-05-11
Last Modified: 2008-02-26

Good Morning,

   I have what I expect is a simple question.

  Recently I Setup a new CISCO 1721 and did most of the configuration through SDM, and then finished with the CMD interface. Unit is working well, Routing, NAT and serving Internal DHCP, as I expected.

   However, the SDM forced the WIC Ethernet (10Mb) to the LAN, and the Base Ethernet (10/100Mb) to the WAN.  

   Since I have a some Gig ports on the switch and some high speed devices requesting DHCP services on the LAN, and a relatively slow Satellite down link on the WAN, I am wondering if there is any reason for this, or can I simply edit the config and swap the ports.  

Question by:jsilberberg
    LVL 20

    Expert Comment

    If all is working fine, no need to swap the interfaces.  
      Having a faster LAN side interface wouldn't make any real difference since your WAN connection is so much slower than even 10 Mbps.  Swapping the interfaces would make more sense if you're going to be running a ton of traffic right back out the LAN interface, such as configuring the 1721 to route between several busy VLANs for a switch connected to the LAN interface.


    Author Comment



       You are correct. It works as defined. But I have a potential for a DMZ or 802.11 and want to be able to add another adapter at a latter point to the second WIC position.

       Additionally, all the DHCP requests are handled by the 10 Mb adapter and the switch has to deal with this interface.

       An most importantly the next person in would have to figure out why it's backwards from common sense :-)

    LVL 20

    Accepted Solution

    As I said, if it's working fine don't sweat it - for what you're using it for it's not going to matter.  But you can always swap them if it bothers you or the next person.


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