MDNS Resource Records are cache by the controller and maintains an expiry timer.
AirGroup will support the following TTL values for the resource records (RR) in the cache.
- TTL = 120 seconds
- RR with host name as RR name (e.g. A, AAA, HINFO etc)
- RR containing host names in rdata
- TTL = 75 minutes
- all other RRs
Cache refresh timer shall be run for:
1. Wired servers.
2. Wirelss servers only if active wireless discovery knob is enabled.
Environment : Both Wired and Wireless Airgroup servers are connected.
Network Topology : (Wired Airgroup server) Airprinter-------Controller ---------AP - - - - Wireless Apple TV (Wireless Airgroup server)
If wireless refresh is turned off, auth process shall inform mdns about user idle for wireless devices and cache entries shall be removed at that point of time.
If wirelss refresh is on, mdns shall continue to send refresh packets and will keep updating cache based on response received.
For wired devices, mdns shall not be able to find out from auth if the AirGroup server is still present or not and hence, for wired devices, refresh shall always be done.
After refresh request is sent out, a 3 second window shall be provided for the AirGroup server to respond. Beyond this time frame, any responses coming from devices shall be considered unsolicited and shall be dropped.
Enabling of "active-wireless-discovery" can be verified through "show airgroup status".
Details of cache entries and ageout can be seen by running the below command:
(Abilash-lab-router) (config) #show airgroup cache entries