A Cisco router receives an IPv4 packet destined for . The router has a single static route configured as follows: `ip route 192.168.10.0 255.255.255.0 10.1.1.2`. Arrange the steps of the router's lookup and packet forwarding process in the correct sequential order from first to last.
- 1The router receives the IPv4 packet destined for on an ingress interface.
- 2The router performs a longest-prefix match lookup and matches the destination to static route prefix .
- 3The router identifies next-hop IP address and initiates a recursive lookup in the routing table.
- 4The router resolves to connected subnet entry associated with interface GigabitEthernet0/1.
- 5The router encapsulates the IP packet into a Layer 2 frame and forwards it out interface GigabitEthernet0/1 toward .
Answer
The correct order of steps for processing a recursive static route lookup is: (1) Receive the IPv4 packet on an ingress interface, (2) Match the destination IP to the static route prefix , (3) Identify next-hop IP and initiate a recursive lookup, (4) Resolve the next-hop IP to connected route on interface GigabitEthernet0/1, and (5) Encapsulate the packet into a Layer 2 frame and transmit out GigabitEthernet0/1.
When a static route is configured using a next-hop IP address rather than an explicit exit interface (e.g., `ip route 192.168.10.0 255.255.255.0 10.1.1.2`), Cisco IOS performs a recursive lookup process. The router first matches the packet's destination IPv4 address to the static route entry. Next, it extracts the next-hop IP address and performs a second routing table lookup to find which interface connects to that next-hop subnet. Once the exit interface is identified from a connected or secondary route, the router encapsulates the packet in a Layer 2 frame and sends it out the resolved interface.
Step-by-Step Solution
Key Concept
IPv4 Static Route Recursive Lookup Mechanism