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New Contributor
Posts: 2
Registered: ‎05-02-2013

Second Controller DHCP Question

We are in the process of adding another 3600 mobility controller to our existing (master) unit.  And so far it's going okay, and most of the process makes sense.

 

However, I had a question about the DHCP pools... we utilize the onboard DHCP for the "guest" SSID.  Am I correct in thinking that if I replicated that DHCP setup exactly the same on the secondary (local) controller, it would possibly hand out an existing leased IP that the master controller might have already issued?  Do they tell each other anything about that?

 

So I should split the DHCP range pools between the controllers, so they couldn't possibly issue the same IP?

 

Thanks for any clarification you can provide!

 

MVP
Posts: 4,238
Registered: ‎07-20-2011

Re: Second Controller DHCP Question

[ Edited ]
You will need to create a dhcp pool for that controller so they don't conflict , those controllers won't sync the dhcp bindings .
Thank you

Victor Fabian
Lead Mobility Engineer @ Integration Partners
AMFX | ACMX | ACDX | ACCX | CWAP | CWDP | CWNA
Super Contributor II
Posts: 429
Registered: ‎01-19-2011

Re: Second Controller DHCP Question

We have a customer with this setup and I can confirm that the bindings are syncd between a master and local device if the same pool is configured on both.

MVP
Posts: 4,238
Registered: ‎07-20-2011

Re: Second Controller DHCP Question

In reality you are not syncing you just created another dhcp pool handing out the same IPs but each controller is not aware of each pool
and this applies to master - backup or master - local
There's certain things that are local to each controller :

VLANs
Login admins
SVIs
NTP
Among a couple of other things
Thank you

Victor Fabian
Lead Mobility Engineer @ Integration Partners
AMFX | ACMX | ACDX | ACCX | CWAP | CWDP | CWNA
Super Contributor II
Posts: 429
Registered: ‎01-19-2011

Re: Second Controller DHCP Question

Whether the information is "syncd" or the local controller stores the info when it hears the DHCP excahnges the info is there. If you do a "show ip dhcp bindings" on the local it lists the info the same as it does on the master - lease times etc.

MVP
Posts: 1,412
Registered: ‎11-30-2011

Re: Second Controller DHCP Question

interesting, im quite sure that an Aruba employee said this wouldn't be synced. which version are you running?

New Contributor
Posts: 2
Registered: ‎05-02-2013

Re: Second Controller DHCP Question

We're running 6.1.3.6-AirGroup on the two controllers, and so far in my testing I do not see the "local" controller showing any of the DHCP bindings that the master has issued.  So I am going to stick with keeping them unique ranges for our use.

 

MVP
Posts: 4,238
Registered: ‎07-20-2011

Re: Second Controller DHCP Question

 

I currently have the same setup Master/Local with the same IP DHCP POOLs (Same name, IP Space) and I currently don't see these syncing .

 

Maybe you can see this behavior if you have a client roaming from one controller to another and since its in the same VLAN/IP Space when the device request the same IP address it already had it gets the same one (if available of course)

 

 

 

 

Thank you

Victor Fabian
Lead Mobility Engineer @ Integration Partners
AMFX | ACMX | ACDX | ACCX | CWAP | CWDP | CWNA
Super Contributor II
Posts: 429
Registered: ‎01-19-2011

Re: Second Controller DHCP Question

Both controllers my customer have were running 6.1.3.8. with all APs on the master and the local for failover so theres no roaming between controllers occuring. I had to go to site to investigate another issue but while I was poking around doing the usual checks, I noticed the IP pool was the same on both controller and pointed out that this was probably bad practice. But they could not provide two separate pools of sufficient size to accomodate all clients and didn't seem bothered when I told them the pool was exhausted. I was even more surprised to see the lcoal reporting all the IP info that the master had handed out.

Well you live and learn.

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