★ Frequent capwap tunnel down on some APs

Traditional Master-Backup AC Networking

The site is the master standby AC + FIT networking, FIT AP number 150 +, after 10 days of normal operation there are several APs dropped.

Dropped APs connect to different access switches.

1. Packet loss occurs when AP drops

From 172.X.X.X to 172.X.X.X (TW102-AP-107) 
------------------------------------------ 
Response from  172.X.X.X  : bytes = 32 hours = 7ms TTL=254 
Response from  172.X.X.X  : bytes = 32 hours = 7ms TTL=254 
Request timed out. 
Request timed out. 
Request timed out. 
Request timed out. 
Response from  172.X.X.X  : bytes = 32 hours = 6ms TTL=254 
Request timed out. 
Request timed out. 
Request timed out. 
Request timed out. 
Response from  172.X.X.X  : bytes = 32 hours = 6ms TTL=254 
Response from  172.X.X.X  : bytes = 32 hours = 6ms TTL=254 
Response from  172.X.X.X  : bytes = 32 hours = 5ms TTL=254 
Response from  172.X.X.X  : bytes = 32 hours = 6ms TTL=254 
Response from  172.X.X.X  : bytes = 32 hours = 6ms TTL=254 
Request timed out.

2. Query AP drop cause: Failed to retransmit message, retransmission failed.

3. According to the reason for AP drop suspected to be the intermediate link there is a blockage caused by the retransmission failure of the drop; check the access switch port situation, there is a drop in the port rate of the part of the AP only 100M situation.

xxx-AP-107 (TWxxx-FSW-001：GE2/0/9)
GE2/0/9              UP   100M(a)F(a)   T    1   
GE2/0/10             UP   1G(a)   F(a)   T    1    
GE2/0/11             UP   1G(a)   F(a)   T    1    
GE2/0/12             UP   1G(a)   F(a)   T    1   
xxx-AP-208 (TWxxx-FSW-001：GE3/0/19)
GE3/0/15             UP   1G(a)   F(a)   T    1    
GE3/0/16             UP   1G(a)   F(a)   T    1    
GE3/0/17             UP   1G(a)   F(a)   T    1   
GE3/0/18             UP   1G(a)   F(a)   T    1   
GE3/0/19             UP   100M(a)F(a)   T    1   
xxx-AP-411 (TWxxx-FSW-001：GE3/0/8)
GE3/0/5              UP   1G(a)   F(a)   T    1    
GE3/0/6              UP   1G(a)   F(a)   T    1    
GE3/0/7              UP   1G(a)   F(a)   T    1    
GE3/0/8              UP   100M(a)F(a)   T    1    
GE3/0/9              UP   1G(a)   F(a)   T    1  

4. Due to more frequent AP drops, mirroring packet captures on the access switch ports revealed that a large number of multicast traffic is regularly received.

5. The VLAN generating the multicast is also put through on the switch port, so congestion occurs resulting in packet loss

1. Layer 2 isolation 

2. Circumventing the receipt of large amounts of multicasts on a regular basis, e.g. by changing VLANs and removing devices that send large amounts of multicasts