When a Cisco router processes an ingress IPv4 packet destined for a remote network, it executes a deterministic evaluation sequence to determine the forwarding path and transmit the frame. Place the operational steps in the correct chronological order from packet ingress to egress frame encapsulation.
- 1Extract the target IP address from the destination field of the IPv4 header.
- 2Search the routing table and select matching entries based on the longest prefix mask (Longest Prefix Match).
- 3Compare route metrics to break ties if multiple identical prefix routes originate from the same protocol.
- 4Identify the designated next-hop IP address and outgoing egress interface.
- 5Resolve the next-hop Layer 2 MAC address via ARP and encapsulate the packet into a new Ethernet frame for transmission.
Answer
The correct evaluation sequence begins with extracting the destination IPv4 address, followed by performing Longest Prefix Match lookup in the routing table, evaluating protocol metrics for equal prefix ties, resolving the next-hop IP and egress interface, and finally resolving ARP to rewrite Layer 2 headers for frame transmission.
Router forwarding logic follows a mandatory sequence: packet header inspection, route selection via Longest Prefix Match (LPM), tie-breaking via metric for matching prefix length, identification of exit interface/next-hop IP, and Layer 2 frame encapsulation via ARP lookup.
Step-by-Step Solution
Key Concept
Router Forwarding Decision Logic