Soru

Zorluk: Çok zorRouting Concepts and Dynamic Routing Protocols

An enterprise enterprise router has learned routes to the destination network 172.16.10.0/24 from multiple dynamic routing sources and static configurations. The routing table currently evaluates path determination during active traffic forwarding. Which of the following operational behaviors correctly describe how the router selects and processes these routes? (Select TWO).

  1. The router compares Administrative Distance (AD) first when multiple routing protocols advertise the exact same destination prefix, selecting the route with the lowest AD to populate the routing table.Cevap
  2. When forwarding a packet, the router evaluates Longest Prefix Match (LPM) prior to Administrative Distance, preferring a /26 route over a /24 route regardless of protocol trust rating.Cevap
  3. C
    If two identical prefixes are learned via OSPF (AD 110) and EIGRP (AD 90), the router places both in the active forwarding table and load-balances using metric calculations.
  4. D
    Static routes with an assigned Administrative Distance of 1 are overridden by dynamic OSPF routes whenever the physical link metric for OSPF drops to 0.

Cevap

The correct selections are the statements regarding Administrative Distance selection for identical prefixes and Longest Prefix Match precedence during packet forwarding.
Administrative Distance is used to choose the most reliable protocol path when identical prefixes are advertised by different protocols. However, during packet forwarding, Longest Prefix Match takes absolute precedence, meaning a more specific prefix (/26) will always be chosen over a less specific one (/24) regardless of how the route was learned.

Adım Adım Çözüm

1
Analyze route selection hierarchy for identical prefixes learned via different sources.
Administrative Distance (AD) determines which protocol's route is populated into the routing table when identical destination subnets exist.
Lower AD values indicate higher protocol trustworthiness.
2
Analyze packet forwarding decision logic for populated routes of varying prefix lengths.
The router applies Longest Prefix Match (LPM) to select the most specific subnet mask.
LPM supersedes AD because AD only determines entry into the routing table, whereas LPM rules active packet forwarding across all table entries.

Anahtar Kavram

Route Selection Precedence (Longest Prefix Match vs Administrative Distance vs Metric)
Bu soruyu puanla