#StackBounty: #router #wifi Bad WLAN routing behaviour when switching AP

Bounty: 50

I have come across a number of variations on the problem described below with router/access-points and WiFi range extenders from various manufacturers.

  • All devices are wireless.
  • LAN/WLAN made up of several general-purpose router/switch/access-point devices, or WLAN extenders, all working on the same SSID. These are from common manufacturers such as NETGEAR and TP-Link.
  • Only a single device acts as an Internet router.
  • There is only a single DHCP server.
  • Access-point-A and Access-point-B are connected by wired LAN.

The following sequence describes the scenario:

  1. Client-device-1 is connected to Access-point-A
  2. Client-device-2 is also connected to Access-point-A
  3. Applications on Client-device-2 are communicating with applications on Client-device-1, typically using TCP.
  4. Client-device-2 is moved in space so that it switches to Access-point-B.
  5. Communication between the applications ceases (fails).
  6. Network trace on Client-device-1 shows (TCP) packets arriving from Client-device-2 and packets being sent in the reverse direction but it seems that those packets fail to arrive at Client-device-2.
  7. Client-device-2 continues to have good Internet access (which actually goes via the router in Access-point-A).

To me it feels like the routing (packet-forwarding) cache in Access-point-A does not notice that Client-device-2 is no longer available via itself, even though packets from Client-device-2 are arriving via its wired interface.

If Client-device-2 is initially connected to Access-point-B then there are no problems.

enter image description here

Any suggestions as to the cause of the problem, other than just rubbish router/access-point firmware, would be appreciated.

Use of quality managed products such as Ubiquiti’s UniFi never seems to show such issues.

Get this bounty!!!

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