API to get Info from router

I assume that you're talking about the associated device list.
In nwk_globals.c, there is the array associated_devices_t AssociatedDevList[NWK_MAX_DEVICES];

the structure of associated_devices_t has the following format:

typedef struct
{
  UINT16 shortAddr;                 // Short address of associated device
  uint16 addrIdx;                   // Index from the address manager
  byte nodeRelation;
  byte devStatus;                   // bitmap of various status values
  byte assocCnt;
  linkInfo_t linkInfo;
} associated_devices_t;

You can then use the utility function in AddrMgr.h called AddrMgrExtAddrLookup to look up the extended address
of each device in this table.

Thanks for your reply. I will look into.