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Move DHCP server from Router to Switch


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#1 brotakul

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Posted 06 December 2018 - 01:44 PM

Hi,

I recently purchased a smart switch to extend the wired network. Right now, my network configuration is as follows:

 

ISP line (fiber/ONT, 1Gpbs) -> WiFi Router (TP-Link Archer C2) -> Smart Switch (TP-Link T1500G-8T)

 

Wired clients are currently connected only to the switch, at least until i run out of ports, and the Router connects all the wireless clients. I went for a smart switch out of curiosity for the control it can give me while extending my home network. The thing is though, i would much rather have the DHCP run on the switch than the router and have the Archer only authenticate over pppoe and pass the connection to the switch. I don't know how exactly to do this. The only way i can think of this actually working would be to add yet another AP on the switch to handle all the wireless connections instead of the router and limit the router to the authentication like i said before. Then, the switch would be the first device handling the DHCP. Otherwise, i fear the wireless clients will not get IPs from the switch.

 

Does DHCP server need to be "in front" of clients (or between the clients and the internet) to do the DHCP, or it doesn't really matter where the device running the DHCP server is located inside the network?

 

Thank you! 


Edited by brotakul, 06 December 2018 - 01:46 PM.


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#2 sparky97

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Posted 06 December 2018 - 03:04 PM

Hello brotakul,

 

DHCP utilizes MAC addresses (Layer 2) to help assign IP addresses (Layer 3) to devices.  With this said, as long as your DHCP server is in the same VLAN as the AP, it should be able to handle serving IPs to your wireless devices.

 

Some helpful materials:

 - How DHCP Works

 - DHCP for Wireless Clients

 

Additionally, according to the manual of your AP, on page 59, it mentions that you can turn your DHCP service off on the WiFi as long as there is another DHCP server on the network.

 

I hope this helps! :)



#3 brotakul

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Posted 06 December 2018 - 03:11 PM

Thanks a lot!

 

Anyway, i checked my switch again and it doesn't have DHCP server as i tought, only DHCP relay which i learned it's something else :) So it seems i'm stuck with the DHCP on the router in this configuration. I was confused since i was also "playing" with the emulator of a managed switch on TP-Link website which actually had DHCP server implemented, so i thought mine has it too. It's not the case unfortunately.

 

But thanks again for your reply!



#4 sparky97

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Posted 06 December 2018 - 03:47 PM

Ah, yes.  DHCP Relay would be helpful for spanning DHCP to networks in different VLANs, but not so helpful for a DHCP server.

 

You could still leverage a free DHCP server on a computer to offload the DHCP from the Router.  I'm not sure if that's an option for you, but you could use:

 

- Open DHCP Server

 

I've had great experience using this in the past as a simple DHCP server.


Edited by sparky97, 06 December 2018 - 03:48 PM.


#5 falcon17

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Posted 06 December 2018 - 03:57 PM

Hi,

I recently purchased a smart switch to extend the wired network. Right now, my network configuration is as follows:

 

ISP line (fiber/ONT, 1Gpbs) -> WiFi Router (TP-Link Archer C2) -> Smart Switch (TP-Link T1500G-8T)

 

Wired clients are currently connected only to the switch, at least until i run out of ports, and the Router connects all the wireless clients. I went for a smart switch out of curiosity for the control it can give me while extending my home network. The thing is though, i would much rather have the DHCP run on the switch than the router and have the Archer only authenticate over pppoe and pass the connection to the switch. I don't know how exactly to do this. The only way i can think of this actually working would be to add yet another AP on the switch to handle all the wireless connections instead of the router and limit the router to the authentication like i said before. Then, the switch would be the first device handling the DHCP. Otherwise, i fear the wireless clients will not get IPs from the switch.

 

Does DHCP server need to be "in front" of clients (or between the clients and the internet) to do the DHCP, or it doesn't really matter where the device running the DHCP server is located inside the network?

 

Thank you! 

Why not have ISP -> Switch -> Wifi Router



#6 brotakul

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Posted 06 December 2018 - 04:02 PM

I don't know if it works. Since the router does the authentication, is the traffic between the switch and the wired clients possible? I mean it would be something like ISP -> switch -> wired PC...



#7 falcon17

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Posted 06 December 2018 - 04:04 PM

How I have it setup in our environment is ISP -> Firewall -> Switch -> AP/WIFI



#8 brotakul

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Posted 08 December 2018 - 02:01 PM

Hi again,

I'd like to ask you guys a different question, but i won't start another thread for this, i hope it's ok.

 

So, the network config is like this:

 

ISP/ONT -> Router1 (PPPoE AUTH, LAN, WiFi SSID1, DHCP ON: 192.168.0.x, 255.255.255.0) -> Smart switch (wired clients on DHCP of Router1) -> Router2 (static IP Router1's DHCP, LAN, WiFi SSID2, DHCP ON: 192.168.1.x on LAN, 192.168.0.x on WAN, 255.255.255.0)

 

I barely managed to get internet working on Router2 and get rid of IP issues by reverting from DD-WRT to stock firmware. Now it works flawlessly, but as a network extension on Router2, i'd like all wireless/wired clients from Router1/switch/Router2 to be able to see each other. I tried to disable DHCP on Router2 so it's clients would get IPs from DHCP server on Router1, but the clients wired to it won't get IPs assigned for some reason, maybe i did something wrong.. 

 

Anyway, is there anything to be done to join the 2 networks?

 

Thanks!

 

LE: seems i have to set a static route on Router1. Studying possible solution... :)

 

LLE: OK, so i found the solution on the internet (seems a lot of people are facing the same "cascading routers" challange :) ). 

Router2 needs to be on the same subnet as Router1, just outside the DHCP range. Router1 has DHCP range set on 192.168.0.100-199, so i set Router2 LAN port IP ar 192.168.0.2. Also, on Router2, i disabled firewall, DHCP and NAT. I connected Router2 to Router1 via LAN-LAN (switch mode). 

Now it seems i can ping and see all clients from both routers. Job done, it was easier than expected. I hope everything works as expected when i'll move Router2 in place and connect all it's clients, now it's just swapped out and in testing mode. 


Edited by brotakul, 08 December 2018 - 03:55 PM.





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