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ianngrh
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Silly Question About DHCP Server Mikrotik

Tue Sep 24, 2019 8:04 am

Hi Mikrotik Masters and Guru.

I have a silly question about DHCP server that running on bridge and it's still bugging me.
Is it possible to make different dhcp pool on each port of bridged interface?

I know it's obviously silly and most of people will tell me to remove the bridge and run dhcp server on each interface.
But what I want to achieve is because I want to run only 1 hotspot server because I don't want user to asked to relogin again when moved to another floor.
In other hand, I want to differentiate the IP address to make my troubleshoot easier.

And what I know, another router like nomadix can achieve this. But the price is crazy like hell :D

Please see design below:
topology.jpg

Thank you in advance
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mkx
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Re: Silly Question About DHCP Server Mikrotik

Tue Sep 24, 2019 9:13 am

Is it possible to make different dhcp pool on each port of bridged interface?

No, it's not possible.

But what I want to achieve is because I want to run only 1 hotspot server because I don't want user to asked to relogin again when moved to another floor.
In other hand, I want to differentiate the IP address to make my troubleshoot easier.

While it might help you debug things, it will affect roaming users ... Let's put the hotspot aside for a moment and have a look at the workings: whenever user moves from one AP to another, one of the following two things happen:
  1. adjacent AP is using same SSID (but different BSSID). In this case client (station) assumes that it's same L2 network and will thus register to the new AP but will skip renegotiating IP address (via DHCP). This makes roaming process fairly quick and, if the signal strength of the old AP wasn't degraded too much, doesn't cause any notable delays for user.
    However, this means that station takes over its old IP address with it and your troubleshooting isn't much easier (IP address of client only tells you which AP it was connected to while it was last renegotiating IP address).
  2. adjacent AP is using different SSID, which means that device has to perform full new registration ... which includes registering to the new AP (when user might have to enter credentials if any form of encryption is configured on AP) and (re)negotiation of IP address. In the case where it's actually same DHCP server serving both old and new APs, the new IP address might even be the same as before, but client has no means of knowing that and it still has to go through whole DHCP lease procedure.
    If IP address changes, this means major service degradation as all ongoing connections have to be torn down.

When you throw in hostspot, then the case #2 above normaly includes new hotspot registration.

If it was possible what you're asking about, the roaming scenario would become case #1 above (because you definitely want to have same SSID on all APs to ease the roaming), but it can't be as you explicitly want clients to change IP address when changing AP.
 
ianngrh
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Re: Silly Question About DHCP Server Mikrotik

Mon Sep 30, 2019 10:18 am

Thank you very much for your response and answer @ MKX
If it was possible what you're asking about, the roaming scenario would become case #1 above (because you definitely want to have same SSID on all APs to ease the roaming), but it can't be as you explicitly want clients to change IP address when changing AP.
Yes, what I want is using same SSID on all access point but with different dhcp pool on each port. Because from my perspective and case I can track and troubleshoot where the device located based on IP address of the device. And I am still curious about that.

After studying the mikrotik dhcp-server wiki for few days I think I can get this by using dhcp relay option. But in this case my access point should support and act as dhcp relay and I need to create dhcp server as many as access point I have. I'm planning to check if my current access point can be used as dhcp relay and try to use this kind of configuration. I will post again the result.
 
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PeterFreeman
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Re: Silly Question About DHCP Server Mikrotik

Mon Sep 30, 2019 11:10 am

Hi there,
Just a thought...
If you are using MikroTik routers as the Access points, then you could configure them all using CAPsMAN and see quite clearly on which AP and radio the wireless client is registered.
 
ianngrh
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Re: Silly Question About DHCP Server Mikrotik

Mon Sep 30, 2019 12:19 pm

Hi PeterFreeman,

Thank you for your thought and I appreciate it. My concern is when I know the IP address of client I know where it's connected without opening any winbox or another tools first :)
Currently I am using unifi UAP-LR on my office. I am also considering cap / map as one access point option and still looking for it's review and configuration references, especially for the roaming parts.

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