An experience case where the AP at a certain site cannot be registered and the error \"Unsupported discovery type\" is reported
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Network Topology
AC and AP Layer 2 Networking
Problem Description
The AP adopts Layer 2 registration, the AP address is obtained normally, the AC and the AP can be pinged, but the AP cannot be registered with the AC.
Process Analysis
Let's first check in accordance with the general thinking:
1. First check the configuration, the basic configuration of AP registration is done correctly, and the serial number is no problem.
2. The AP can obtain the address normally, and the AC and the AP can be pinged.
3. Debug wlan capwap on both the AC and AP to collect information and follow the AP registration process to see which stage is stuck. First look at the debug information of the AP:
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*Jan 1 00:03:26:362 2014 H3C CWC/7/FSM: Enter Discovery state. *Jan 1 00:03:26:363 2014 H3C CWC/7/EVENT: Fill discover req.wtu=1.model=WAP722S.wt drv info: []. subslot=0.licensetype=1.ret=0x40010001. *Jan 1 00:03:26:363 2014 H3C CWC/7/EVENT: Fill discover req.ap=1.model=WAP722S.licensetype=1. carry wt info is unnecessary. *Jan 1 00:03:26:364 2014 H3C CWC/7/SND_PKT: Sent discovery request with SeqNum 0 to AC 255.255.255.255:5246. *Jan 1 00:03:26:364 2014 H3C CWC/7/SND_PKT: Verbose info for discovery request sent to AC 255.255.255.255:5246, length=155. ................................... *Jan 1 00:03:26:365 2014 H3C CWC/7/SND_PKT: Sent discovery request with SeqNum 0 to AC 224.0.1.140:5246. *Jan 1 00:03:26:365 2014 H3C CWC/7/SND_PKT: Verbose info for discovery request sent to AC 224.0.1.140:5246, length=155. ................................... *Jan 1 00:03:26:365 2014 H3C CWC/7/TMR: [AP 1] Create Max Discovery Interval Timer. *Jan 1 00:03:32:360 2014 H3C CWC/7/TMR: MaxDiscovery Interval timer expired. *Jan 1 00:03:32:361 2014 H3C CWC/7/EVENT: Fill discover req.wtu=1.model=WAP722S.wt drv info:[].subslot=0.licensetype=1.ret=0x40010001. *Jan 1 00:03:32:361 2014 H3C CWC/7/EVENT: Fill discover req.ap=1.model=WAP722S.licensetype=1.carry wt info is unnecessary. |
Judging from the debug information of Ap, the AP has been sending discovery messages to AC, but has not received a response message from AC. It may be that the AP did not really forward the messages from the port, or it may be an intermediate link. A problem caused the AP not to receive the response packet from the AC.
4. Let's see what the collected debug information shows from the AC.
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*Jun 12 21:26:27:267 2019 H3C CWS/7/RCV_PKT: Received discovery request with SeqNum 0 from AP at 10.xxx.2.xxx:58629. *Jun 12 21:26:27:267 2019 H3C CWS/7/RCV_PKT: Received discovery request from AP at 10.xxx.2.xxx:58629, Length=155. ................................... *Jun 12 21:26:27:267 2019 H3C CWS/7/EVENT: usApcbConnectingCnt is 0. *Jun 12 21:26:27:267 2019 H3C CWS/7/ERROR: Failed to process discovery request from AP with serial ID 21980xxxxxxxxxxx2Z: Unsupported discovery type. *Jun 12 21:26:27:267 2019 H3C CWS/7/ERROR: Failed to proc pkt msg from AP at 10.xxx.2.xxx:1509. MsgType = 1. |
From the debug of the AC, we can see that the AC received the discovery request from the AP, but the AC reported an error: Failed to process discovery request from AP with serial ID 21980xxxxxxxxxxx2Z: Unsupported discovery type. It seems that the AC does not support AP discovery The requested format.
Let's look back at the AC configuration at this time to see if there are any special commands. At this time, we found such a command in the AC configuration:
wlan capwap discovery-policy unicast
Generally, an AP can discover an AC and establish a CAPWAP or LWAPP tunnel through unicast, multicast, and broadcast methods. After configuring this command, the unicast discovery policy function is enabled. The AC only responds to APs that send unicast Discovery request packets, and does not respond to APs that send multicast or broadcast Discovery request packets. That is, only APs that are discovered by unicast are allowed. Establish a CAPWAP or LWAPP tunnel connection with the AC.
From here we have found the root cause of the problem. The AP broadcasts a request to the AC. Since the AC has enabled the unicast discovery policy function, the AC does not respond to the AP, so the AP cannot register.
Solution
Delete the wlan capwap discovery-policy unicast command, and the problem is solved.