Mr.1977

Q: Dchp and dns services from two different servers, possible?

I would like to know if this is possible please.

 

I have a Fortinet router providing dchp to my network, and I need to set up internal dns for a printer on a static ip address.

 

Is it possible to set up a primary zone so that I can add this printer using a different server e.g. My Mac server running 10.6?

 

Or is there a better way to do this?

 

Thank you very much.

Mac Mini, Mac OS X (10.6.4)

Posted on Aug 27, 2012 6:06 PM

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Q: Dchp and dns services from two different servers, possible?

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  • by MrHoffman,

    MrHoffman MrHoffman Aug 28, 2012 8:38 AM in response to Mr.1977
    Level 6 (15,637 points)
    Mac OS X
    Aug 28, 2012 8:38 AM in response to Mr.1977

    You're seemingly somewhat confused about both DNS and DHCP (or I'm simply misinterpreting some of the phrasing of the question, and which is always distinctly possible), so here's a quick sketch that might help:

     

    DHCP and DNS are entirely separate functions.

     

    DHCP passes out IP addresses to hosts, using a pool of addresses.

     

    DNS passes out translations from host names to IP addresses, or from IP addresses to host names.

     

    Yes, you can have multiple DHCP servers on a network, so long as the address pools involved do not overlap; that is, that the DHCP servers do not offer overlapping IP address ranges, and so long as none of addresses offered by the DHCP servers overlap any static IP addresses you've assigned.  It's not typical to do this, and it's not particularly address-efficient, but it does work.  (I have and manage several networks configured this way.)

     

    A static-addressed printer is just a host that's outside of any DHCP address pool, or that's been explicitly configured within a DHCP server to always receive the same IP address for any address requests. 

     

    When a network device or a server requires a fixed IP address, it's fairly common to just hard-set the address in the device, and ensure that the assigned address is outside of the DHCP address pool.

     

    In general, the static-addressed hosts are usually listed in local DNS services, and the client boxes with dynamic addresses assigned by DHCP usually aren't. 

     

    As a general rule, client boxes get the dynamic stuff and depend on servers, and the servers and server boxes get static addresses.

  • by Mr.1977,

    Mr.1977 Mr.1977 Aug 28, 2012 10:38 AM in response to MrHoffman
    Level 1 (0 points)
    Aug 28, 2012 10:38 AM in response to MrHoffman

    Mr. Hoffman thanks again, just so I am clear would the following work.

     

    DCHP Server 1 IP Address 192.168.200.1

     

         DCHP Address pool: 192.168.200.5 to 192.168.201.252   

     

    DCHP Server 2 IP Address 192.168.200.2

     

         DCHP Address pool: 192.168.202.5 to 192.168.203.252

     

    Printer IP Address = 192.168.200.3

     

    Also when you said it isn't the most efficient way, could you let me know what is? I can google the specifics, if you can't go into to much detail.

     

    Thanks

  • by MrHoffman,

    MrHoffman MrHoffman Aug 28, 2012 2:40 PM in response to Mr.1977
    Level 6 (15,637 points)
    Mac OS X
    Aug 28, 2012 2:40 PM in response to Mr.1977

    The inefficiency is simply inherent; it's due to the use of two pools where you might get better loading from one pool.  You have a thousand IP addresses tied up between those two pools.

     

    Those IP pools are also comparatively large, too; do you need ~500 users to be active in each of those DHCP servers? 

     

    Secondary to the DHCP pools and related activity, simply having that many clients in one big subnet tends to cause network problems, and particularly if those ~500 boxes or (if that's one subnet) those ~1000 boxes are doing much of anything past requesting IP addresses; a gigabit or a WiFi can very easily be swamped by that many users.

     

    And if you do have those two pools, then you either have two subnets and some routing between them, or that's one very big IP subnet configured that contains both of those ranges. 

     

    You have only a very few static addresses left, whether you're using a /23 configuration and the 192.168.200.0 to 192.158.201.255 range, or a /22 configuration and the 192.168.200.0 to 192.158.203.255 range as one (big) subnet.

     

    And FWIW, some devices just can't handle an IP subnet larger than a /24.  Which yours most definitely is.

     

    And FWIW (2), my preference is to reserve low-numbered addresses for static-addressed boxes, as they're shorter and easier to remember, and (here) I'd probably run the DHCP ranges right up to .254 - unless there's something else up there.

     

    And FWIW (3), I don't see a need for a second DHCP server block here, just to add a static address.

  • by Mr.1977,

    Mr.1977 Mr.1977 Aug 28, 2012 3:58 PM in response to MrHoffman
    Level 1 (0 points)
    Aug 28, 2012 3:58 PM in response to MrHoffman

    Thanks. I only need about 360 IP addresses max. The reason I added the second pool was what if the first DCHP server went off line, or became unavailable. Which mine did last weekend. Oh and I didn't have a back up solution for the DNS services either, so it went kind of south from there.

     

    Just trying to get a solution using two Mac servers, on how to setup a network for 400 devices, where if one server fails, I can switch over to the second one asap, and DNS and DCHP are all working like nothing happened.

  • by MrHoffman,

    MrHoffman MrHoffman Aug 28, 2012 5:59 PM in response to Mr.1977
    Level 6 (15,637 points)
    Mac OS X
    Aug 28, 2012 5:59 PM in response to Mr.1977

    Ah; OK.  So this doesn't seem to involve the static IP assignments and the printer, so part of my earlier responses probably isn't going to be that appropriate. 

     

    For a more robust configuration at this scale, you would likely want to implement what's called DHCP failover, and probably not two separate servers.

     

    AFAIK, OS X Server doesn't provide DHCP failover, though various other add-on DHCP servers and add-on network services products can provide this capability.   Your Fortinet device might offer this capability; I don't know.

     

    Here's a write-up for ISC DHCP failover, which might provide you with some ideas around what's involved.

     

    And FWIW, management of the DHCP server management was removed from Mountain Lion Server (10.8 server) package and it's now integrated within either the Netinstall support or with the Internet connection sharing; see HT5381.  In other words, DHCP is latent, but manually managed

     

    Choosing and deploying an alternative DHCP server implementation, and particularly one that supports failover, would probably be the best apprpoach.