server with several interfaces

Simon Hobson dhcp1 at
Mon Mar 4 21:00:41 UTC 2019

ITMex <it.compilation at> wrote:

> Hi everyone, I need some help, I need to running isc dhcp server, this
> dhcp server must be able to offer IP address from plenty of VLANs (
> about 15 VLANs ) I wonder if this is possible using VMs?under VMware.
> Please someone can trow me a bone here? if is possible to get a
> example to achieve this mission.

In general, that should be no problem.

Assuming no "interesting problems" with the networking under VMware, then there is little needed for this.

1 - Your dhcpd.conf needs to have a declaration for each subnet to be served.

2 - The server needs EITHER an interface on each segment to be served OR there needs to be a relay agent on segments that aren't directly connected. This doesn't need to be all one or the other, it can be any mix.

3 - There needs to be routing in place so that any client in any segment can exchange packets with the server.

To expand on those a bit ...

1 - That's just a case of making sure that your config matches the actual network - including any shared networks you may have.

2 - For locally connected network segments, the server needs an IP address on that interface that's in a subnet on that segment. If it's a shared network (ie more than one subnet on the one segment) then only one IP in any of the subnets is needed - the "magic" of the shared network statement takes care of that.
For remote networks, you need a relay agent on the remote segment. This is often in the router, but doesn't have to be.

3 - For renewals, clients can talk directly to the server. So there must be 2 way routing between any client and the server. It doesn't have to take the same route as broadcast packets using the relay agents - but in most networks it will do.

So really it's down to how you want to do it - connect the DHCP server to every network, or use relay agents. The ISC server does run on VLAN interfaces - so that gives you more options !

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