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thunderrd
@lemurraya.com

thunderrd

Anon

ZyXel AMG1312-T10B - how to reserve IPs for absent comps

I have the above router and am new to it.

I would like to have the address range 192.168.1.2-192.168.1.10 reserved for wired computers, of which .2-.6 are always present in the network. Computers .7-.10 come and go frequently, but need to be assigned the same IPs each time they rejoin the network.

I also want the addresses 192.168.1.11-192.168.1.20 reserved for wireless connections.

Right now, I have the IP pool set to start at .2 and end at .20 [pool size 18], and have set static leases for .2-.6. However, the wireless devices are being assigned IPs starting at .7, which I don't want. How do I prevent DHCP from assigning the IPs .7-.10 to wireless devices, and force DHCP to begin the wireless device pool at .11?

I thought about starting the DHCP pool at .11 instead, so the wireless devices are always assigned IPs above .10, but the router does not allow me to set static leases for the wired network that are outside the pool. This is frustrating, because it seems like the easy answer. Is there another way to accomplish this?
JPedroT
Premium Member
join:2005-02-18

JPedroT

Premium Member

I doubt you can have that kind of granularity on a DHCP server running on a CPE.

Mainly because there usually is no way to for the DHCP server to know if a device is on the LAN or WLAN.
ThunderRd
join:2010-02-28
Thailand

ThunderRd to thunderrd

Member

to thunderrd
I forgot to mention there is a managed switch between the router and the wired clients. Does that give me options?
JPedroT
Premium Member
join:2005-02-18

JPedroT

Premium Member

Not really, this can be accomplished if you run a DHCP server where you have full control and not just access to a limited subset of features as you mostly do on CPE's. Albeit I do not know the AMG1312 device, so I do not know the limitations of it, but generally CPE's does not have very flexible solutions for DHCP.

As for a solution, if you can use your switch to do dhcp relay, you can use that info to set a side a pool for all devices connecting through the switch.
Or if you switch supports option 82 tagging you can use that also, but then your DHCP server also needs to support option 82.

So yes, you can do it, but you most likely need a "proper" DHCP server installation and not a CPE deployed DHCP server.
Look into using Raspberry PI or if you have NAS or if you have any other server on your LAN that can run DHCP server software.
JPedroT

JPedroT to thunderrd

Premium Member

to thunderrd
Just reread your first post, quick question, you know the mac address of all the wired computers? If so, then you should be able to make a static entry for all of them, so that 2 to 10 will be reserved. That way wifi devices will not get them but randomly from the rest of your pool.
ThunderRd
join:2010-02-28
Thailand

1 edit

ThunderRd

Member

[EDIT: my posts are moderated ATM, and this one has been placed before the next one. Actually, it happened in the reverse.]

Interesting, I think I posted the above information regarding DHCP snooping minutes before you sent your last response.

As to the MAC addresses, I either have them already or can get the ones I don't have. I wasn't aware that a static lease could be set for a non-present device, but I suppose that would be an acceptable solution. I will look into that.
ThunderRd

ThunderRd to JPedroT

Member

to JPedroT
Thank you, JPedroT, for your time.

I see in the switch configuration that there is an area for DHCP snooping, DHCP snooping bindings, and DHCP Interfaces, but if you'd be so kind, could you give me a bit more detail as to exactly what I have to do in order to accomplish what I am after?

This is a link to the manual for my switch, model Linksys LGS-308: »www.sysnetcenter.com/doc ··· uide.pdf

I think the pertinent information begins on page 44. This switch seems to support DHCP snooping and option 82, but I've checked the manual for the router/DHCP server, and unfortunately it does not. Does that make what I want impossible, since there is no 'proper' DHCP server?

And, thanks again for the help.
JPedroT
Premium Member
join:2005-02-18

JPedroT

Premium Member

As mentioned, I do not know the features of the AMG DHCP server, but if you got all the mac addresses you most likely can reserve those, by manually entering them somewhere.

If you do not and can not use that approach, you most likely need a standalone DHCP server, that supports option 82 or at least can make rules based on relays etc.
ThunderRd
join:2010-02-28
Thailand

ThunderRd

Member

Yup, that is the easiest way, and it works. I am able to reserve the IPs for the absent devices, and when they connect, they connect to the correct IP.

Thank you again, you've been a great help.