How to get the extended pan ID at the application layer, when a router joins into a new network with zstack (zigbee pro), ?

hi,

 When i set the coordinator's zgApsUseExtendedPANID to be {0x12,00,00,00,00,00,00,00 }, and router's to be all 0.

Then when the router joins into the network, how to get the extended pan ID at  the application layer?

Thanks!