(Dis)advantages of Sharing an IP address vs Distributing with DHCP

Discussion in 'Mac Accessories' started by zmsmith, Jan 11, 2010.

  1. zmsmith macrumors newbie

    Joined:
    Jan 11, 2010
    #1
    What are the performance differences for a home network (6 devices) using DHCP to distribute a range of IP addresses or sharing one public IP address. For some reason my network won't work when I try to distribute a range of IP addresses, but it does work when I share a single IP address. I am trying to figure out if it is worth trying to make the network work using DHCP.

    I am also just generally curious to the differences in network performance and what issues they each may cause. Also any advice as to why my network would function properly with one setting and not the other would be appreciated.

    Thanks
     
  2. balamw Moderator

    balamw

    Staff Member

    Joined:
    Aug 16, 2005
    Location:
    New England
    #2
    What router are you using, and what is the nature of your connection.

    I think you are misinterpreting the meaning of the settings. TCP/IP basically requires each node to have it's own address. I would venture to guess that "share a single IP" means one public IP and 6 private ones (for which the router distributes addresses with DHCP). The 6 private addresses are presented as one using Network Address Translation (NAT).

    The other case probably tries to get 6 separate addresses, which is not supported by your ISP.

    B
     
  3. zmsmith thread starter macrumors newbie

    Joined:
    Jan 11, 2010
    #3
    Thanks for the quick response. I'm glad to have a better understanding of what's going on.

    I have an older time capsule (500 mb) to which I have one wired multimedia box and 5 laptops.

    It sounds like I don't have a choice to which configuration to use for my network, but I'd still be curious to know why someone with a choice between the two would choose one configuration over the other.

    Thanks again
     
  4. balamw Moderator

    balamw

    Staff Member

    Joined:
    Aug 16, 2005
    Location:
    New England
    #4
    The default configuration for home networks these days is that your ISP provides you with a single public IP address (either by PPPoE or DHCP) and you must use NAT to connect multiple computers/etc... to that single shared public IP address. In this mode the private nodes still get their own IP addresses from the router via DHCP. (I think the other mode may turn on DHCP, but not NAT).

    How are you connected to the internet? This is actually the important question in sorting this out.

    You always have choices! The question is, is there a reason you want to make things more complicated than the default?

    NAT does increase network latency a bit, since the router has to figure out which private IP to send things to, but unless you have a special deal with your ISP for multiple public IP addresses you don't usually have a choice but to use it.

    B
     
  5. Joga macrumors newbie

    Joined:
    May 5, 2013
    #5
    Thanks, balamw! Very informative explanation on this subject.
     
  6. Tesselator, May 6, 2013
    Last edited: May 6, 2013

    Tesselator macrumors 601

    Tesselator

    Joined:
    Jan 9, 2008
    Location:
    Japan
    #6
    mb = megabits
    MB = megabytes

    Bandwidth.

    Typically (at least here is Japan) an account with multiple fixed IP addresses allows the full service bandwidth over each connection simultaneously. So if the service is 100mb and there are 8 fixed IP addresses you would be able to DL or UL at about 10MB/s on each of your 8 computers. You could also bridge the connections I think too and get 80MB/s if I'm not mistaken.

    With a service providing one dynamic IP (or fixed for that matter) the machines have to share the 10MB/s max bandwidth. So if your kids are downloading torrents or games over their xbox your ability to surf the web becomes very slow.

    There are also service contracts which provide multiple fixed IP addresses over a single line speed too tho. That will have some benefits for internet servers you might wanna set up but not much.

    The first option I described usually isn't worth it. That service is typically pretty expensive ($300/mo or more) and for a home user it isn't (can't be) taken advantage of often enough to make a significant difference. Install something like MenuMeters and watch how seldom you max out your connection's bandwidth. Mine is maxed out about 10 hours per week and I'm a really heavy downloader. :D My connection is 120mb and I share that among 4 machines and various handheld wireless devices - I almost never notice any degradation. Sometimes I do tho... maybe once or twice a month for a few minutes.
     

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