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Wireless AP is up but not broadcasting SSID - AP Uptime shows N/A

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Information

 
TitleWireless AP is up but not broadcasting SSID - AP Uptime shows N/A
Symptoms
  • Wireless AP is up but not broadcasting SSID
  • AP Uptime shows: Uptime: N/A
Environment
  • IdentiFi Wireless
  • All software versions
  • VPN Tunnel
  • L2/L3 Tunnel
Cause
When the path between an AP and the Controller is across a VPN, MPLS, or any other type of layer-2 / layer-3 tunnel, MTU needs to be configured to prevent packet fragmentation
Resolution
From a PC at the wireless controller location, verify what size MTU packets are capable of being transmitted without fragmentation from a dos prompt of a pc (192.168.0.2 IP address = Access Point)
C:\>ping 192.168.0.2 -f -l 1500

Pinging 192.168.0.2 with 1500 bytes of data:
Packet needs to be fragmented but DF set.
Packet needs to be fragmented but DF set.
Packet needs to be fragmented but DF set.
Packet needs to be fragmented but DF set.

Ping statistics for 192.168.0.2:
Packets: Sent = 4, Received = 0, Lost = 4 (100% loss),

C:\>
Try a lower MTU: 
C:\>ping 192.168.0.2 -f -l 1400

Pinging 192.168.0.2 with 1400 bytes of data:
Reply from 192.168.0.2: bytes=1400 time=15ms TTL=57
Reply from 192.168.0.2: bytes=1400 time=16ms TTL=57
Reply from 192.168.0.2: bytes=1400 time=16ms TTL=57
Reply from 192.168.0.2: bytes=1400 time=15ms TTL=57

Ping statistics for 192.168.0.2:
Packets: Sent = 4, Received = 4, Lost = 0 (0% loss),
Approximate round trip times in milli-seconds:
Minimum = 15ms, Maximum = 16ms, Average = 15ms

C:\>
Once MTU is found that does not require fragmentation, change AP to this new MTU:
     1.  Click AP Tab > APs dropdown menu >
     2.  Click AP in question to select
     3.  Click Static Configuration Tab > then modify Tunnel MTU to desired value
     4.  Click Save button
 
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