dhcp pool allocation q ?

pinkiaiiipinkiaiii Posts: 216Member
done with ccna long time ago,but still come back to different topics to keep most of what ive learned fresh.
So the other day was just thinking out on random how does any routher with dchp pool decide what ip to give to host,since got many pc and other devices at home and ip's on local network seem just random from the .255-10 reserved pool of class c
Since knowing nature that in cisco mac addresses on different protocols have a role wonder is there some factor when dhcp handles out ip,or is it some random formula it comes on with,when handing ip's

Comments

  • hurricane1091hurricane1091 Posts: 918Member
    pinkiaiii wrote: »
    done with ccna long time ago,but still come back to different topics to keep most of what ive learned fresh.
    So the other day was just thinking out on random how does any routher with dchp pool decide what ip to give to host,since got many pc and other devices at home and ip's on local network seem just random from the .255-10 reserved pool of class c
    Since knowing nature that in cisco mac addresses on different protocols have a role wonder is there some factor when dhcp handles out ip,or is it some random formula it comes on with,when handing ip's

    I set up a DHCP pool to study DHCP snooping for the CCIE this week. From my experience, it started at the first available IP address. When I released that address though, I got the next available address, even though the previous one should have been available. This is not something I put much time or research into, but I would expect that the DHCP server just hands them out in numerical order, and it is not based off of any sort of algorithm. Not impossible, and I have nothing to back this up except for what I have seen in the lab.
  • OctalDumpOctalDump Posts: 1,722Member
    I read through the RFCs for DHCP a while ago, and the nitty gritty of DHCP message types, and I don't think that the RFC specifies how the server gives out addresses. It is possible for clients to request specific addresses, and it is possible for most servers to allocate specific addresses based on MAC or other details.

    Also, there are different ways for addresses to be released, explicitly or not, so a "free" address might not be "free".

    DHCP is just another one of those areas where you can dig very deep into the protocol and discover all sorts of wonderful, arcane things, that 99.99% of the time don't matter.
    2017 Goals - Something Cisco, Something Linux, Agile PM
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