Accidentally Solving Access Point Roaming Issues.

ShadowMoses
2019-08-04T01:09:36Z

I'm sharing in case some of you are having a similar issue at work or at home, and to hear your opinion and/or similar stories!

I've been using Ubiquiti access points in my home for a few years now, and overall, they've worked very well. 3 APs giving near perfect 5GHz VHT80 coverage on DFS channels. LAN transfers are about 600-650mbit on laptops, which has proven to be plenty for wireless clients in my home. Keep in mind that this is a pretty basic setup... besides the APs, there's just the ISP provided GPON ONT which is also a typical all-in-one ISP solution (router, switch, AP, firewall, DHCP server...) with it's Wi-Fi turned off.

As I said, I was pretty happy with the results, however there was one feature that I could never get to work just right; roaming. You could be walking around the house watching a live stream and the stream would pause for 5-8 seconds until the roaming transition was over. Strangely, with VoIP calls, roaming would be about 3-5 seconds. Even enabling fast roaming features (which I believe is simply 802.11r) on the AP's controller would not give the results I was looking for. After days of tweaking TX power settings, channel selection and trying to implement Minimum RSSI (which I ended up not using), I finally gave up and resigned myself to the 4-6 seconds (oh, the humanity) of roaming time.

Fast forward to about two months ago and I added a new router to the setup (UBNT ER-4) and a switch (UBNT USW-24). Setup went smooth, already had some cat.6 cabling around the house, now it was time to actually use it. Had some fun setting up a guest Wi-Fi network on it's own VLAN, which was always a concern of mine; having "untrusted" devices connect to my network. The access points do client isolation on guest networks by default, but in my mind it wasn't enough as I have some file servers and time machines on the network.

Anyways, a few days after doing the setup I'm walking around the house with a livestream on my mobile and suddenly realize that it's not losing the connection. I try with a VoIP call and it worked flawlessly. I start walking around faster and still, the phone is roaming without an issue. I was very excited!

I'm thinking it must be the router that somehow solved the roaming issue. My first theory was that the DHCP server on the ER-4 was doing it's thing much faster than the ISP's device, allowing the wireless clients to actually roam faster. So I do a web search and I find some very relevant info. It was a thread on a forum and reddit thread with a sysadmin that was about to give up on the APs because of roaming issues. In both threads, there were replies about what switch were they using.

Apparently, some switches (Cisco and HP were mentioned), have a "MAC aging" interval setting which is way too high by default, or they simply have bugged firmware that doesn't allow the switch to "re-learn" the MAC address of a device on a different switch port. I assume that ISP provided "el-cheapo" gear has similar issues.

So, if you're having roaming issues with your wireless clients, check your switches!!!

Anyways, just wanted to share this story. Thank you for reading. :-)

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