ISC-dhcp subnet limit?

Simon Hobson dhcp1 at
Fri Jan 29 16:30:14 UTC 2016

Rob Morin <rmorin at> wrote:

> Currently we made dhcp-2 a standalone server ...

Did you also edit the ranges on both servers to be non-overlapping ?

One thing you must *NOT* do is have two independent servers with overlapping ranges - down that route lies the path to random strange problems.

Thinking about one bit of your original question. I'm assuming that all requests are coming via remote relay agents - is that correct ?
If so, then the routing doesn't really matter. The inbound interface will be determined by the route(s) available from the relay agent (or client *) to the address(es) it's configured to send the packets to. The outbound interface will be determined by the route(s) available from the server to the gateway interface address (GI-Addr) field in the request packet (or client address *). It doesn't matter (for the DHCP anyway) if there is triangular routing in place - but you need to ensure that any filtering/firewalls allows the packets through.

* When a client has an active lease, it will unicast a renewal request to the server that granted the lest in order to request an extension to it. So you need unicast traffic allowed between clients and server.

Something else to look at is logging. IIRC Syslog defaults to synchronous logging for a lot of things - and that means a lot of disk activity logging the DHCP activities. At the expense of losing some logging if the system crashes, you can configure async logging so there isn't a file sync on avery log message. This can significantly reduce disk activity and improve performance.

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