What does a router do after de-encapsulating a received frame?
After de-encapsulating a received frame, a router performs several tasks:
1. Error Checking: The router examines the checksum or cyclic redundancy check (CRC) field of the frame to verify its integrity. If any errors are detected, the router may discard the frame.
2. Decoding the Layer 2 Header: The router decodes the Layer 2 header of the frame to determine the source and destination MAC addresses. This information is used to determine the next hop for the packet.
3. Forwarding Decision: The router checks its routing table to determine the best path for the packet based on its destination IP address. It selects the appropriate interface (outgoing port) to forward the packet.
4. Encapsulation: Once the outgoing interface is determined, the router encapsulates the packet into a new frame with the appropriate Layer 2 header (e.g., Ethernet header) for the next hop.
5. Transmission: The router then transmits the newly encapsulated frame to the next hop on the network, typically using appropriate physical layer protocols such as Ethernet, WLAN, or ATM.
It’s important to note that routers operate at the network layer (Layer 3) of the OSI model and use logical addressing (IP addresses) to make routing decisions. By de-encapsulating, examining, making forwarding decisions, re-encapsulating, and transmitting frames, routers play a critical role in directing network traffic between different networks.
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