Exclusions versus reservations on static IPs

Posted on 2007-08-11
Last Modified: 2013-11-05
I am using SBS 2003 Standard Edition R2. I have a range of IP addresses for the server to assigned via DHCP for the client machines. I have static IPs for the networked priters and fax machines as well as for the server, router, and switch.

Currently, those that required static IP addresses have been excluded from DHCP assigned IPs via exclusions. It seems like someone told me once that it is better to use reservations for this. I had no trouble setting that up for the server as I know its MAC address. I don't, however, know MAC addressed for switches, routers and printers.

Should I just use the exclusions?
Question by:Bert2005
    LVL 38

    Assisted Solution

    by:Philip Elder
    Your switches should be statically assigned with their IPs included in an exclusion.

    Routers should be statically assigned with their IPs included in an exclusion.

    Printers can be done either way. In my experience, setting a DHCP reservation for the printer is the best route to go if there are any future IP management needs. Make sure the printer is set to DHCP as opposed to BOOTP (you can do BOOTP - but you need to enable that view in the DHCP manager).

    Power cycle the printer and watch it pick up a DHCP address in the DHCP management console. You can obtain the MAC address there, or by printing out a configuration sheet on the printer to get it.


    LVL 23

    Expert Comment

    To be honest, why change anything that is working? If exclusion is giving you the desire result why change it? I am with the idea of giving static IPs to printers, routers and switches.
    LVL 70

    Accepted Solution

    You can easily find the MAC address of any local device, ping its name or IP address and then use the arp -a command to list the arp cache. You will see the IP addresses and the corresponding MAC addresses of all the machines your machine has contacted recently.

    Using reservations has some advantages - but only if your devices can make use of DHCP features. For example. If you have a file server you might want this always to have the same IP address no matter what so you have two options - set it up as a static IP or set up a DHCP reservation.
    The advantage of the reservation is that even though the IP address is reserved for the specific machine, the file server still goes through the usual DHCP request and renewal process and can get the various DHCP options when the lease is renewed.

    So for example you can set the file server up with a reservation and set the machines preferred DNS server with a DHCP option. If you later change which DNS server you want the machine to use you can change the value in the DHCP option and when the lease is renewed the new DNS server information will be updated.
    LVL 1

    Author Comment

    Thanks guys,

    I believe that is another thing I heard once ormerodrutter. If it ain't broke don't fix it. Other than some magical thing for the network, one benefit is I can see what is what on the server. (J/K..well I can, but I don't think that is a great benefit).

    It is has been working up until now. But, just for the best information, I would like to share how the private side is configured as I don't think I thought about it much prior to doing it.


    100 - server
    10 - printer
    13 - fax
    14 - Networked backup drive

    Workstations on DHCP -- 8, 9, 22, 24, 25, 79, 80

    Name  riverviewpediatrics.local  Type DHCP  Unique ID  RAS
    These are all x.2 through x.7

    Address range for distribution: through

    OK questions:

    1. I guess it's stupid to assign the server a static IP and give it a reservation?
    2. What are the x.2 through x.7 RAS things?
    3. The address range covers the entire scope. I guess with statics assigned and reservations that doesn't matter, but should it have been set up differently?

    Sorry, I am new at this. But, things have been working fine, I must admit.

    LVL 38

    Expert Comment

    by:Philip Elder
    1: No. It is a good idea so that no other devices receive that IP which results in an IP conflict.
    2: When someone VPNs in, they will be served an IP address from that group.
    3: Not sure what you are asking?

    LVL 70

    Expert Comment

    Either use a static IP or a reservation - no point in setting it static AND using a reservation as the reservation will never get used. Most people put the static IPs at one end of the IP range - that way you do not need to use exclusions either. Eg if your network uses - then set DHCP to use IPs - and use the first 20 IPs for static machines, printers and routers etc.

    You could also hive off another chunk of IPs for use with RAS - or you can just RAS us DHCP.

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