A Cisco router receives an IPv4 packet destined for a remote host and evaluates its routing table containing multiple routes from different sources. Place the steps of the router's forwarding decision logic in the correct order from first to last.
- 1Identify all matching routing table entries and select the route with the longest prefix match (most specific mask).
- 2If multiple matching routes have the exact same prefix length, compare their Administrative Distance (AD) values to choose the lowest value.
- 3If multiple matching routes share the exact same prefix length and AD, compare their metric values to select the route with the lowest cost.
- 4Forward the encapsulated packet out the designated exit interface toward the next-hop IP address.
Cevap
The correct sequence of router forwarding decision logic from first to last is: 1) Select the route with the longest prefix match; 2) Compare Administrative Distance if prefix lengths are identical; 3) Compare metric values if AD and prefix lengths are identical; 4) Forward the packet using the selected route's exit interface and next hop.
When a Cisco router makes a forwarding decision, it follows a strict hierarchical evaluation sequence. First, it identifies all routes in the routing table that match the destination IPv4 address and selects the route with the longest prefix match (most specific subnet mask). Second, if there are multiple matching routes with identical prefix lengths, it evaluates Administrative Distance (AD) to pick the route from the most trustworthy routing protocol. Third, if multiple routes share identical prefix lengths and AD values, it compares the metric (path cost) to choose the lowest metric route. Finally, once the single best route is determined, the router forwards the packet out the associated exit interface.
Adım Adım Çözüm
Anahtar Kavram
Router Forwarding Decision Logic Precedence (Longest Prefix Match > Administrative Distance > Metric)