Perle Systems IOLINK-PRO IOLINK-520 - Manual (Page 4)

Introduction
IOLINK-PRO & 520 Reference Manua — 1.3
• Local router will receive the data frame and strip off the MAC portion. The resulting IP frame will be examined to
determine the destination IP address.
• Local router will look in its routing table to find the IP address of the router to send the IP frame to next. The local
router will see that the destination router is the next router.
• Local router will look in its ARP cache to find the MAC address of the destination router as determined by the IP
address in the routing table.
• Local router will rebuild the complete frame with a new MAC header indicating the MAC address of the destination
router. The local router does not alter the destination IP address, so the destination IP address will still be the IP
address of the destination station.
• Destination router will receive the data frame and strip off the MAC portion. The resulting IP frame will be
examined to determine the destination IP address.
• Destination router will look in its routing table to find the IP address of the router to send the IP frame to next. The
destination router will see that the destination IP address is on a locally connected network.
• Destination router will look in its ARP cache to see if it has a MAC address for the destination IP address. If it does
not have an entry, the destination router will generate an ARP request. The destination station will send an ARP
reply.
• Destination router will rebuild the complete frame with a new MAC header indicating the MAC address of the
destination station. The destination IP address once again will be unchanged and remain as the destination station IP
address.
• Destination station will receive the data frame and process it.
If the destination station wishes to send a frame back to the originating station, the process will happen in the reverse
direction.
If the path from the originating station to the destination station causes the frame to pass through more than two routers, the
above process will simply be extended to include the interaction between the intermediate routers.