Wifi Network Best Practices for DHCP and Router Setup

Posted on 2012-08-20
Last Modified: 2012-10-03
I'd like to get some suggestions as to the proper configuration for my network.  I have a wired internet connection with 5 public IP addresses at my hub location where I have a router.  I have three Ubiquiti wireless bridges connecting three other locations where I also have routers.  The routers are all the same model.  I need to provide internet connectivity to all four locations so I'm thinking that I should use DHCP on the LAN side of all four routers, including the one at the hub.  I'm thinking that I need to seperate the networks so that I don't have address conflicts.  Any advise on how to set this up would be greatly appreciated.
Question by:EricHoma
    LVL 5

    Expert Comment

    The traditional role of routers especially in a configuration with 3 or more sites is to act as a proxy forwarding the information to the DHCP server.  This would create a centralized configuration where one DHCP server is responsible for managing and distributing addresses to the various subnets.   On those routers acting as a proxy you would setup IP helpers so that the broadcast requests for DHCP would make it to the correct server.  ie. is your dhcp server

    Router1#configure terminal
    Enter configuration commands, one per line.  End with CNTL/Z.
    Router1(config)#interface Ethernet0
    Router1(config-if)#ip helper-address

    Author Comment

    In laymans terms?  I guess I need to learn about IP Helpers...

    I guess your saying that all DHCP addresses should be issued/controlled by the router that is attached to the wired WAN and that the other routers (one at each remote site) are only passing that IP through?
    LVL 5

    Accepted Solution

    If you want to learn about IP Helpers here is a pretty good description link:

    The normal method is to centralize on a DHCP server rather than the routers.  It simplifies management in larger DHCP/vlan groups.  If you want a single pane of glass view of your scopes then yes learn about and use IP Helpers with centralized DHCP.  

    If you don't really care about the additional management of having DHCP run on multiple devices then you could skip that step and just run DHCP on each router.   Or if you have issues with the links being too slow or going down it would pay to have DHCP on each remote router.  

    Alternatively if having redundancy is important you could setup your main dhcp scope on each remote router and save a portion of the scope for your main router using IP Helper that would allow for DHCP redundancy - in that way whichever DHCP server responds first will get the request.

    It really depends on how you want to set it up.  But the most common configuration you'll find out there for larger sites is single pane of glass for DHCP and IP Helpers to get you there.

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