DHCP and DNS in routed network

JKnott

Why does a routed network make a difference? You can have a DHCP server on each interface. You only need 1 DNS server for your entire network. I have a DNS server enabled for local addresses and use the resolver for external addresses.

johnpoz

@JKnott said in DHCP and DNS in routed network:

Why does a routed network make a difference?

because if pfsense does not have a leg in the network, you can not setup dhcp server.

If you have some downstream networks that are routed at a downstream router, pfsense wouldn't have an interface actually in the network..

Ethereal

@johnpoz
so I have a question around DHCP for remote networks.
Why this feature has not been implemented yet with pfsense? are there any challenges ?
This is quite a common feature (when used with DHCP relay/IP helper) and to me it's a bit absurd that pfsense has to have an interface in the network so it can provide leases.

Cheers!

SteveITS

@Ethereal Something else would have to relay.

DHCP is basically the device asking “can anyone give me an address?” If there were two DHCP servers on a network with different settings, either may answer first.

Ethereal

@SteveITS the relay is always done by the router of the network where the host asking for a lease, sits. These frames are L2 and don't go outside the broadcast domain.

SteveITS

@Ethereal ok but in this scenario that’s not pfSense, correct? If the request is forwarded to pfSense how does pfSense know for what other network it should answer?

johnpoz

@Ethereal pfsense does not support setting a scope for a non directly connected network maybe with the dhcpd that is coming they will that function?

AndyRH

@SteveITS said in DHCP and DNS in routed network:

If the request is forwarded to pfSense how does pfSense know for what other network it should answer?

If pfSense did support this common feature, the relay sees the broadcast, sends a directed packet to the DHCP server including subnet information. The DHCP server responds with the lease information. The relay then responds with a broadcast to the original requester with the DHCP lease information. Works great in large networks.
Maybe the rumors of a change in DHCP server for pfSense will add this feature.

Ethereal

@AndyRH I'm glad to see that there are many people out there asking for this feature to be implemented.

SteveITS

I understand the request now. In a very quick search I found this 7 year old thread saying it doesn't work in Kea but maybe they have added it since.

https://lists.isc.org/mailman/htdig/kea-users/2016-December/000707.html

ref: Replace ISC DHCP server with Kea: https://redmine.pfsense.org/issues/6960

johnpoz

@Ethereal said in DHCP and DNS in routed network:

many people

Define many? If you mean a few here and there as many - ok ;) hehehe

Most networks that get to the stage that they are routing downstream run their own dhcpd, and not off their edge router..

AndyRH

If you use the Customer Service complaint theory, only a low percentage of people will complain, most just go somewhere else.
In the last few months I have seen 3 or 4 posts in some way related to DHCP relay. So 3 times some number that just do something else. That total has to be more than a few dozen. Enough to warrant adding the feature, maybe. If relay is a feature of KEA (I have found no evidence it is) then it would be wise to implement it.
In a lab environment relay would be nice so it can be used for practice.
I am more after the feature to add a reservation in the range, which appears to be a feature. It just makes it easier for me and I do not have IP address OCD so I am cool with "random" reservations.

Ethereal

@johnpoz hahahaha yeah, well in my defense there are a few posts on this forum around this feature. People (like me) are a bit surprised that this is not supported and in the same time a bit disapointed, since it's quite a basic feature.
In the same time, you're not wrong about the dedicated DHCP server.
Myself I have the scopes configured on my 3750x switch, however would love to have them configured on the pfsense box. I love the gui, I can't help it.