The controller and the access points exchange packets using the CAPWAP reliable transport protocol. For each request, a response is defined. This response is used to acknowledge the receipt of the request message. Response messages are not explicitly acknowledged; therefore, if a response message is not received, the original request message is retransmitted after the retransmit interval. If the request is not acknowledged after a maximum number of retransmissions, the session is closed and the access points re-associate with another controller.
You can configure the retransmission intervals and retry count both at a global as well as a specific access point level. A global configuration applies these configuration parameters to all the access points. That is, the retransmission interval and the retry count are uniform for all access points. Alternatively, when you configure the retransmission level and retry count at a specific access point level, the values are applied to that particular access point. The access point specific configuration has a higher precedence than the global configuration.
Through GUI you can configure this as shown in the below. Default retransmit interval is 3s where as default setting for retry count is 5.
Under AP advanced setting page you can configure these values for a given AP. That settings will supersede the global settings if configured. Below shows 1252-c AP configured for 2s retransmit interval & retry count of 4.
“show ap retransmit all” command can be used to verify settings.
(4402-a) >show ap retransmit all Global control packet retransmit interval: 3 (default) Global control packet retransmit count: 5 (default) AP Name Retransmit Interval Retransmit count ------------------ ------------------- ------------------- 3502-d 3 (default) 5 (WLC default),5 (AP default) 1252-c 2 4
If you want to configure this using CLI you can use following commands.
1. Configure the retransmission interval and retry count for all APs globally by entering this CLI command. Interval is a value between 2-5s where as count is a value 3-8.
config ap restransmit {interval|count} all
2. Configure the retransmission interval and retry count value for a specific access point by entering this command.
config ap restransmit {interval|count} Cisco_AP_Name
3. Verification can be done by using following CLI commands
show ap retransmit {Cisco_AP_Name|all}
(4402-a) >config ap retransmit ?
interval Configures AP Control packet retransmission timeout between 2 and 5 seconds.
count Configures AP Control packet retransmission count between 3 and 8.
(4402-a) >config ap retransmit interval ?
<seconds> Configures AP Control packet retransmission timeout between 2 and 5 seconds.
(4402-a) >config ap retransmit count ?
<count> Configures AP Control packet retransmission count between 3 and 8.
(4402-a) >show ap retransmit 1252-c
Global control packet retransmit interval: 3 (default)
Global control packet retransmit count: 5 (default)
AP Name Retransmit Interval Retransmit count
------------------ ------------------- -------------------
1252-c 2 4
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mrn-cciew 
Hi Rasika,
Do you know how AP re-transmit parameters are related to the (fast)heartbeat timeout?
In my scenario when heartbeat timeout expired AP didn’t move to discovery state or try to join another WLC. However, when maximum retransmission count exceeded, AP started discovery process.
This was case in situation when heartbeat timeout run out before maximum retransmission count , as well as vice versa.
Regards,
Marko
Hi Rasika,
How do i to see more fast the information about client in the GUI of controller? There is a parameter for change this, but i forgot.
Can you help me?
Thanks
Regards!
Delfis
Monitor > Client > is the way you get client detail.
Are you looking for something else ?
Rasika
i have configured ap retransmit count 5 and ap retransmit interval 3 but my wlc received the nex message:
%CAPWAP-3-MAX_RETRANSMISSIONS_REACHED: capwap_ac_sm.c:7623 Max retransmissions reached on AP(58:97:bd:0c:3b:a0),message (CAPWAP_CONFIGURATION_UPDATE_REQUEST
),number of pending messages(1)
its wrong? i need to do something?