Wireless Access

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Frequent Contributor II

AP behind MESH link

Hi

 

Customer of mine has setup a MESH link between 2 buildings, distance about 65 meters, so this should be no problem.

MESH consists of AP-277 and AP-215, where the 277 acts as a portal and 215 as a point.

At the far end, the AP-215 has a trunk on the Ethernet port, to a local switch, this way we can trunk the needed VLAN.

This is all good, no problem in the lab.

Behind the MESH link on the LAN on the remote building, he wants to setup 2-3 AP's, that connect to the controller via the MESH link.

This is also working as it should, but the throughput on these AP's are bad, he is experiencing a big difference between upload and download speeds, and generally low speeds.

If we active the SSID on the MESH point, the throughput is normal.

 

I even setup a similar system in my lab, and i can confirm very low speeds on the AP's behind the MESH link, but normal speeds on a SSID on the MESH point.

 

Both systems are running 6.4.4.5.

 

I have used MESH before, but not with CAP's behind the MESH link. Is this normal behavior?

 

Roar Fossen

Guru Elite

Re: AP behind MESH link

First, what is the output for "show ap mesh topology"?  You can PM me with that so I can take a look.



Colin Joseph
Aruba Customer Engineering

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Re: AP behind MESH link

Also for the wired AP profile on the mesh cluster, are you bridging or tunneling the wired port?

When you do a throughput test, not from the WLAN on the mesh point, but from a wired workstation/laptop on the switch hanging off the point, is throughput bad as well?

If you just stand up one SINGLE AP off the switch (off the mesh point), is throughput just as poor or is it normal?

Jerrod Howard
Sr. Technical Marketing Engineer
Frequent Contributor II

Re: AP behind MESH link

Hi

 

We had some initial problems with the mesh topology not forming, but this is now sorted.

We do still see a big difference in Tx and Rx association speeds, but the customer is now testing, whether 802.11a og 802.11g is giving the best results.

 

To answer you question, when we connect a single client to the switch, the throughput is good, as good as one would expect in such a solution. The wired AP profile on the mesh point is tunneling the VLAN to the switch.

 

If we connect an AP to the same port on the switch, and the AP connects to the controller thru the mesh link, and broadcasts a SSID, the throughput suddenly is bad.

 

But as we have had some problems with a second AP-277, and we are now using an AP-215 as point, we will wait until Aruba TAC has come up with a solution to our AP-277 problem.

 

Thanks anyway

 

Roar

Re: AP behind MESH link

So what is the output of your 'show ap mesh topology', specifically the mesh link SNR/RSSI? With the 802.11ac radios, esp with the 27x platforms, you can EASILY over-drive the radios (putting too much RF into the APs which essentially 'distorts' the quality of the signal'. If you are using AP-277s at 65m at max power, I could easily see the RSSI being too high and you needing to drop the Tx power on each side to improve backhaul throughput. 

 

When you tested a wireless client, was the client on the 2.4Ghz or 5Ghz radio off the CAPs?

 

You have full gig/full all the way through, there's no 10/100 power injectors in the mix between point and portal, etc? I've seen a 10/100 injector on a gig rated switch result in a 10-half port negotiation and throughput under load was atrocious. Since your wired performance from the switch is solid, I don't think that would be it. 

 

As far as APs on the far side of a mesh link, do you have any MTU-specific configs applied to any of your AP groups? Did you create a new AP group for the APs in the other building hanging of the mesh point? Because you are running the mesh in tunnel mode AND the APs are tunneling GRE to the controller, if you set any specific MTU on the mesh link or on the CAP group, you can hit an issue where packets are getting fragmented. If you have set smaller than default MTUs on your wired infrastructure between the two, that can cause issues as well. Something else to look in to. An easy way to test would be to take a dual ethernet port AP to the building off the point, wire the AP's ENET0 to the switch and let it come up as a CAP, and apply a tunneled wired profile to the ENET1 port and test throughput from a laptop. If you see the same poor performance, you know you have a dual-tunnel/MTU issue. If not, then you know you have an RF issue on the other side.

 

The other fix to remove MTU/dual tunnel issues would be to set the mesh link to bridge, but then you need to make sure you untag the proper native VLAN on each side and tag the proper VLANs for tagged backhaul on the uplink ports on the point and portal. If you decide to change it, DO NOT do it if the mesh link needs to be active as it will drop and if config isn't exact, will drop the other side, or test it in the lab before rolling out.

 

I've done plenty of CAPs behind a mesh point and have never seen a system performance issues like that unless it's an RF issue. 

Jerrod Howard
Sr. Technical Marketing Engineer
Frequent Contributor II

Re: AP behind MESH link

Hi Jerrod

 

A bunch of very good points, i'll bring them along to the customer.

The mesh topology output was at first that we didn't see a topology, but when we got the system up, we saw a RSSI of 16 on 11g and 10 on 11a.

This is kinda low, but this building are used by students on a random basis, so they are aware of the low thruput.

 

I'm not sure if he tested with 11a or 11g on the client, but he mainly used default mesh profiles when testing and that one is using 11a. But i'm only guessing.

 

The customer do have a tunnel in a tunnel to this site and we have played a bit with the MTU.

I have asked him to do a test to find where the MTU fragmentation point is, after he did this, he was able to increase the download for the wireless client significally. This tells me that they had a too low MTU configured last time they tested.

 

I will point my customer to this post, this way he can read it himself and take actions.

 

Thanks

Re: AP behind MESH link

I should have asked first, is this AOS or IAP? 

 

When you run a 'show ap mesh topology' on AOS, you should only see an RSSI for the mesh link.

Jerrod Howard
Sr. Technical Marketing Engineer
Frequent Contributor II

Re: AP behind MESH link

Hi

 

My initial post says sw version 6.4.4.5, so this is AOS.

 

Yeah, i have seen the RSSI values, and they are not good, but ok.

We hope to see an increase as we get the second AP-277 up and running at the point side of things.

But we had some issues when building mesh with two AP-277, Aruba TAC is looking into that one.

 

As i wrote, running 11g, we saw RSSI value of 16 and 10 running on 11a.

I asked the customer to mail me the output, be he left to catch a plane :(

 

Roar Fossen

 

Re: AP behind MESH link

Roger that, sorry, missed the 6.4.4.5. 

 

RSSI would be MUCH higher than 16 with a pair of 277s. 277-215, that could be depending on the orientation of the 215 and what is between the two.

 

Keep us filled in on TAC. Something is amiss, TAC should be able to run it down.

Jerrod Howard
Sr. Technical Marketing Engineer
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