Need to use DHCP Relay AND Server on the same pfSense setup, no L3 switch at disposal

mleone87 · Jul 17, 2020, 2:25 PM

Hi,
I'm migrating a couple o indipendent SonicWall appliances to a HA setup based on a couple of XG7100 routers.
All it's good but the SonicWalls permit server AND relay functionalities via "IP Helper" and similiar functionalities.
I dont have any L3 switch at my disposal to delegate this functionality, can you suggest a solution for that? Can NAT be used for that?

Thanks

JKnott · Jul 17, 2020, 7:32 PM

@mleone87

Nope. DHCP uses a specific port, which can be used for either the relay, the server, not both. To use both, you'd have to put one on different port, but that's not something you can change. A L3 switch wouldn't do it either. BTW, a L3 switch and router are functionally equivalent.

johnpoz · Jul 17, 2020, 8:03 PM

So your trying to do relay and also run dhcpd on different network of pfsense? Yeah can't really do that, to be a relay pfsense can not run dhcpd on any interface.. Atleast in 2.4.5p1

mleone87 · Jul 17, 2020, 8:53 PM

Yes, I would use relay on some interfaces(2 or 3 btw), and for some other the pfsense dhcp server functionalities. I was thinking to a L3 switch because maybe the software onboard permit that(I've read about this during some researches on the topic).

No solution except moving relayed dhcp to pfsense itself?

thanks

JKnott · Jul 17, 2020, 9:02 PM

@mleone87

Why do you need a relay? You'd normally only use one if there wasn't a DHCP server on the LAN segment.

mleone87 · Jul 17, 2020, 9:40 PM

@JKnott there is an AD server with DHCP/DNS enabled, just for historical reasons, not practical. All networks relayed actually relay to that server. The migration from sonicwalls to pfsense would be a simple porting in the 1st phase and a decommission of AD DHCP in the 2nd phase

my real question is why on sonicwall si so simple to do that :)

thanks

johnpoz · Jul 17, 2020, 11:07 PM

@mleone87 said in Need to use DHCP Relay AND Server on the same pfSense setup, no L3 switch at disposal:

my real question is why on sonicwall si so simple to do that :)

Do what run a dhcpd and relay on the same box.. Not some screaming feature that would have much use to be honest.. You either run dhcpd on pfsense, or you use it as a relay.

Most larger networks that would run their own dedicated dhcpd have little use of the pretty basic dhcpd on pfsense. But if its going to route your L3, then dhcp relay would be needed.. To be honest if your a AD shop, it would make zero sense to move dns and dhcp to pfsense. Are you moving away from AD completely? If so then yeah you can run dhcpd on pfsense, and sure provide dns.. But your already a AD shop, and still going to be - I wouldn't want to move those services to pfsense.

JKnott · Jul 18, 2020, 1:28 AM

@mleone87 said in Need to use DHCP Relay AND Server on the same pfSense setup, no L3 switch at disposal:

my real question is why on sonicwall si so simple to do that :)

How does it sort out which requests go to the local DNS and which get relayed?

mleone87 · Jul 19, 2020, 11:16 AM

@johnpoz we will move all functionalities to pfsense box since DHCP/DNS feature of AD are only for address reservation

@JKnott I'm not the most expert networking GUI on the planet but you the software bind the port per interface and not for all interfaces like pfsense does, it's the most easy thing to do :)

johnpoz · Jul 19, 2020, 11:31 AM

@mleone87 said in Need to use DHCP Relay AND Server on the same pfSense setup, no L3 switch at disposal:

DHCP/DNS feature of AD are only for address reservation

Didn't answer my question - are your devices members of the AD? If your going to continue to use AD, members of and uses login.. It makes no sense to move DNS which a vital role in how AD works to somewhere else, and dhcp goes hand in hand with that.

johnpoz · Jul 19, 2020, 11:35 AM

@mleone87 said in Need to use DHCP Relay AND Server on the same pfSense setup, no L3 switch at disposal:

it's the most easy thing to do :)

So code will be submitted to pull this weekend by you I guess??

mleone87 · Jul 19, 2020, 4:04 PM

Here we go, same old story pfSense staff eh?
Blame people to do pull request it's not the best way to handle help req in forums, and it's even worst if you think that I made my client spend a lot of money for a couple of xg7100 probabily in the last ever suggestion about this software again.

I'l put again the original question: How to use DHCP Relay AND Server on the same pfSense setup
It can't be possible because whatever? Fine thanks

Good joob anyway to loose another paying customer ;)

Edit: we can close now since I do not have time to handle other smart guys

JKnott · Jul 19, 2020, 6:10 PM

@mleone87

One thing to bear in mind is that pfSense is built on FreeBSD, which is where many of the limitations come from. Something like this might require change from the FreeBSD team.

jimp · Jul 21, 2020, 6:03 PM

It isn't possible because of the way DHCP relay needs to latch onto upstream and downstream interfaces and the way the DHCP daemon latches onto interfaces.

With significant development work it might be possible to restrict the interface bindings and maybe have it work for some cases, but it's a lot of effort for minimal benefit.

If you have a decent switch, enable DHCP relay/ip helper in the switch for the segments you want to relay, and then you don't have to worry about having pfSense do it.

johnpoz · Jul 21, 2020, 7:12 PM

@jimp said in Need to use DHCP Relay AND Server on the same pfSense setup, no L3 switch at disposal:

but it's a lot of effort for minimal benefit.

Exactly... What 1 user out 50k might have use of this.. And at that they just too lazy or cheap to do it correctly on their L2 infrastructure...