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Zorluk: OrtaIPv4 Static Routing

A Cisco router configured with the static route `ip route 172.16.10.0 255.255.255.0 10.1.1.2` receives an IPv4 packet destined for 172.16.10.45172.16.10.45. Place the steps performed by the router to process and forward this packet in the correct sequential order from first to last.

  1. 1The router receives an IPv4 packet destined for host 172.16.10.45172.16.10.45 on an ingress interface.
  2. 2The router evaluates its routing table and matches the destination IP to the static route prefix 172.16.10.0/24172.16.10.0/24.
  3. 3The router extracts the next-hop IPv4 address (10.1.1.210.1.1.2) specified in the static route entry.
  4. 4The router performs a recursive lookup in the routing table for 10.1.1.210.1.1.2 to determine the outbound egress interface.
  5. 5The router encapsulates the IPv4 packet into a Layer 2 frame and transmits it out the resolved egress interface.

Cevap

The correct sequence of router operation steps is: (1) Packet arrival at ingress interface, (2) Destination matching against static route prefix 172.16.10.0/24, (3) Extraction of next-hop IP 10.1.1.2, (4) Recursive routing table lookup for 10.1.1.2 to find egress interface, and (5) Layer 2 encapsulation and forwarding out the resolved exit interface.
When a router receives a packet destined for a subnet covered by a next-hop static route, it first matches the destination prefix, identifies the next-hop IP, and then executes a recursive lookup to find the directly connected egress interface before encapsulating and transmitting the frame.

Adım Adım Çözüm

1
Inspect incoming packet destination
Destination IP 172.16.10.45172.16.10.45 is identified.
Routing processing begins as soon as a packet enters the router.
2
Lookup destination in IPv4 routing table
Matches `172.16.10.0/24` pointing to next-hop 10.1.1.210.1.1.2.
The router performs a longest prefix match against active routing table entries.
3
Extract next-hop address requirement
Next-hop IP 10.1.1.210.1.1.2 is identified.
The static route was configured using next-hop IP syntax rather than directly specifying an exit interface.
4
Execute recursive route resolution lookup
Egress interface (e.g., GigabitEthernet0/1) associated with subnet 10.1.1.0/2410.1.1.0/24 is resolved.
Cisco IOS requires a recursive lookup to resolve next-hop IP addresses to an active, directly connected egress interface.
5
Encapsulate and forward frame
Packet is framed and transmitted out the egress interface toward 10.1.1.210.1.1.2.
Layer 2 headers are constructed after exit interface and next-hop MAC resolution.

Anahtar Kavram

Recursive Lookup for Next-Hop IPv4 Static Routes
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Konular

IPv4 Static Routing

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