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Wireless Networks Thread, DHCP Redundancy in Technical; Hi. We've got a second server here setup to do AD & DNS redundancy, and ive been trying to do ...
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    DHCP Redundancy

    Hi.

    We've got a second server here setup to do AD & DNS redundancy, and ive been trying to do the same with DHCP.
    After some reading around, i concluded that what i need to do was:

    Have a range covering a certain amount.
    Have server A exempt half one half of that range. And server B exempt the other half.
    have the same reservations on both servers.
    All sorted.

    Problem is, that it doesnt work.

    For example.
    Server A has a range of 172.17.5.10 to 172.6.254.
    Exclusion of 172.17.6.1 to 172.17.6.254

    And

    Server B has a range of 172.17.5.10 to 172.6.254.
    Exclusion of 172.17.5.10 to 172.17.5.254

    Both have the same reservations. gateways, ect;

    Doesnt appear to work though.
    Theoretically if i disable DHCP on Server A and renew an address, B should pick it up. Doesnt happen though.

    Ideas?

    Thanks in advance all. .

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    Geoff's Avatar
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    Windows DHCP failed miserably in this regard for me also. I'm using ISC DHCPd with failover on Linux machines now instead.

    Failover with ISC DHCP

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    Tbh, i'd prefer to get it working on windows.
    Its only a temporary thing anyway, the networks getting nuked in the summer. .

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    Geoff's Avatar
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    It took me 12 hours of not getting it to work on Windows. It took me 2 hours of setting up on *nix. Was a no brainer.

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    Michael's Avatar
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    It is a good question - why isn't redundancy on DHCP straight forward? What about Windows Server 2008; does this support DHCP redundancy?

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    it wont, server 2 will know that the ip address is valid and so wont attempt to renew it. i think once it's expired then server 2 will dish it out an ip from its range.

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    So when server 1 has no more addresses to hand out, server 2 will pick up the rest?
    Thats a bit messed up, as theres no redundancy there?

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    RabbieBurns's Avatar
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    Quote Originally Posted by Geoff View Post
    It took me 12 hours of not getting it to work on Windows. It took me 2 hours of setting up on *nix. Was a no brainer.
    Aye ive got it setup like that as well. Took me longer to figure out how to get the two servers times in sync for dhcp failvoer to work than it did to configure dhcp failover ;p

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    Geoff's Avatar
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    NTP is one of the first things I install on new *nix servers.

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    RabbieBurns's Avatar
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    it was the timezone I had set wrong on one of them. Had it set for just GMT rather than the london zone, so it was exactly 1 hour out.

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    Quote Originally Posted by boomam View Post
    So when server 1 has no more addresses to hand out, server 2 will pick up the rest?
    Thats a bit messed up, as theres no redundancy there?
    nooo... Pc1 will try to renew it's ip, server2 will look at its request and dismiss it as valid. When pc1's ip expires it then looks for a new ip, which it will receive from server2.

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    Quote Originally Posted by bossman View Post
    The first link is basically describing what im doing, having one server serve one half of a scope and the other server serving the other half.
    Not too keen on using 3rd party software to do something that afaik, should work anyway?

    Quote Originally Posted by strawberry View Post
    nooo... Pc1 will try to renew it's ip, server2 will look at its request and dismiss it as valid. When pc1's ip expires it then looks for a new ip, which it will receive from server2.
    So even if ive switched off DHCP on server 1 it wont work?

    Thats a bit rubbish, as surely the entire point of redundancy is to provide that facility when the 'main' part isnt functioning.

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    kinda works for me, It'll ensure that you always have a valid working ip address and if server 1 comes backonline before the end of the lease it can pick up where it's left off.

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    Diello's Avatar
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    We've got it working on Windows here - but instead of excluding half the range, each DHCP server is only set to serve half the range each. We find it load balances perfectly.



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