ArubaOS and Controllers

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Aruba Employee
Posts: 28
Registered: ‎11-19-2007

AP redundancy across a layer 3 boundary

Folks,

I am sure someone has done this before (hopefully) but I figured I would throw it out there for input.

The senario is as follows:
- Master controller at HQ
- Local controller off-site
- Layer 3 connectivity between the two sites, routers using EIGRP to share routes

Things the customer does not want to do:
- Over-complicate the network with VPN or L2TP connections (think 100 off-site locations)
- Add extra hardware

The goal is to have the APs terminating to the local but if it fails terminate to the master. On a regular network VRRP would be set up and the same client VLAN could be on the master and local. On this network we can't have the same client VLAN between the two sites.

My thought is that I can have the same VLAN ID on both the master and local, but they will be different subnets. This will keep the AP happy and it will broadcast the SSID in the event of a fail-over. When there is a fail-over scenario the clients will have to pull a new IP address before they will function, assuming the AP does not go down when it switches to the backup lms-ip.

Anyone have any thoughts or alternate possible solutions that are backed up with some past experience doing this same thing?

TIA! :D
Cheers!
Marcus Wehmeyer
Aruba Employee
Posts: 119
Registered: ‎05-16-2007

Re: AP redundancy across a layer 3 boundary

Hello Marcus. Since you don't have Layer2 between controllers, you'll need to use Backup-LMS set in the AP system profile.

If your VLAN IDs are the same between the local controller and the master you're wanting to have as the backup, then everything is fine.

But if the VLAN IDs are different, you'll want to use "Named VLANs". Better than I can type here, reference named VLANs in the documentation for 5.0 and you'll see exactly what I mean. They work perfectly for what you are looking to do.
Aruba Employee
Posts: 28
Registered: ‎11-19-2007

Re: AP redundancy across a layer 3 boundary

Thanks Brian. I wasn't clear but I was planning on using the backup-lms method for this deployment.

Do you know if the AP will drop the SSID while it re-terminates to the backup controller? This could be the preferred situation because the clients would drop and then do a dhcp request that would get them on the right subnet automatically.

TIA! :D
Cheers!
Marcus Wehmeyer
Aruba Employee
Posts: 119
Registered: ‎05-16-2007

Re: AP redundancy across a layer 3 boundary

Correct. The BSSIDs will reset during failover causing a media disconnect to the client which prompts it to do another DHCP...so as far as IP space, it won't matter because the client will get a new IP address anyway.

Hope that helps.
Aruba Employee
Posts: 28
Registered: ‎11-19-2007

Re: AP redundancy across a layer 3 boundary

Redundancy is working fine, the AP is connecting to the master at HQ when we force the local to fail. The client loses the wireless connection and re-associates, it tries to pull dhcp but fails. I have to disable and enable the wireless interface on the laptop in order for it to pull dhcp when it is connected to the back-up controller. The client is a Latitude E6400 running Windows XP with SP3, Dell 1510 WLAN card.

If this sounds like something that needs to go to TAC let me know...I feel like we are having a client issue now, the Aruba gear is doing what it is supposed to.
Cheers!
Marcus Wehmeyer
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