Controller-less WLANs

Why slave IAPs at times reboot due to reason "Master transitioned to local".
Problem:

At times we may find slave IAPs rebooting due to reason “master transitioned to local” and the only reason for such reboot reason would be if master beacons are not reaching out to the slave IAPs.  When slave misses 8 consecutive heartbeat from master in a row, it will change its role to Master. When it start receiving Master Beacon form Old master again, it will change its role back to slave after a reboot, with the reboot reason “master transitioned to local”.



Diagnostics:
  • We will have to console into problematic slave and execute “debug-master-beacons” by logging the session.
  • Once “debug-master-beacons” IAP will continuously print the master beacons received from Master IAP.
  • As shown below, initially slave was receiving master beacons from Master IAP. After 8 consecutive heartbeat miss in a row, slave took the role of Master.

 

[  521.729222] asap_mob_pkt_rcv:2221 Receive master-beacon, from 18:64:72:c8:20:a0 10.17.171.94 (bond0), version 4                ⇒ Master beacon from VC

[  521.850095] asap_mob_pkt_rcv:2249 Receive beacon from vlan 1 pvid 1 vs. uplink_vlan 0

[  522.543577] asap_send_hierarchy_message:3540 Send hierarchy-beacon, beacon-ip 10.17.171.89 (eth1), state Slave

[  522.663441] asap_send_hierarchy_message:3542 tx failed.

[  522.727884] asap_mob_pkt_rcv:2221 Receive master-beacon, from 18:64:72:c8:20:a0 10.17.171.94 (bond0), version 4                ⇒ Master beacon from VC

[  522.848765] asap_mob_pkt_rcv:2249 Receive beacon from vlan 1 pvid 1 vs. uplink_vlan 0

[  523.543564] asap_send_hierarchy_message:3540 Send hierarchy-beacon, beacon-ip 10.17.171.89 (eth1), state Slave                 ⇒ VC unplugged. No beacon received 1

[  523.663424] asap_send_hierarchy_message:3542 tx failed.

[  524.543567] asap_send_hierarchy_message:3540 Send hierarchy-beacon, beacon-ip 10.17.171.89 (eth1), state Slave                 ⇒ No beacon received 2

[  524.663428] asap_send_hierarchy_message:3542 tx failed.

[  525.543562] asap_send_hierarchy_message:3540 Send hierarchy-beacon, beacon-ip 10.17.171.89 (eth1), state Slave                 ⇒ No beacon received 3

[  525.663421] asap_send_hierarchy_message:3542 tx failed.

[  526.543563] asap_send_hierarchy_message:3540 Send hierarchy-beacon, beacon-ip 10.17.171.89 (eth1), state Slave                 ⇒ No beacon received 4

[  526.663432] asap_send_hierarchy_message:3542 tx failed.

[  527.543067] asap_send_hierarchy_message:3540 Send hierarchy-beacon, beacon-ip 10.17.171.89 (eth1), state Slave                 ⇒ No beacon received 5

[  527.662934] asap_send_hierarchy_message:3542 tx failed.

[  528.543568] asap_send_hierarchy_message:3540 Send hierarchy-beacon, beacon-ip 10.17.171.89 (eth1), state Slave                 ⇒ No beacon received 6

[  528.663431] asap_send_hierarchy_message:3542 tx failed.

[  529.543566] asap_send_hierarchy_message:3540 Send hierarchy-beacon, beacon-ip 10.17.171.89 (eth1), state Slave                 ⇒ No beacon received 7

[  529.663420] asap_send_hierarchy_message:3542 tx failed.

[  530.543565] asap_send_hierarchy_message:3540 Send hierarchy-beacon, beacon-ip 10.17.171.89 (eth1), state Slave                 ⇒ No beacon received 8

[  530.663417] asap_send_hierarchy_message:3542 tx failed.

[  530.725951] i am a potential master now

[  530.771820] (02:45:31) !!! Slave ---> Pot-Master                                                                               ⇒ It took the role of Master.


Solution

We will mostly see such issues when IAPs of same cluster are scattered across different switches in different location or when IAPs forming a cluster from different geographical locations through MPLS network. In such network deployment, WLAN admin needs to ensure there are no delays involved or network related issues. We may encounter such reboot reason even due to some physical layer issues such as Ethernet cabling or network interface for which WLAN admin can swap the ports or change the Ethernet cables.

Version history
Revision #:
2 of 2
Last update:
‎08-08-2016 11:42 AM
Updated by:
 
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