Cisco 100-105 Exam
When a router makes a routing decision for a packet that is received from one network and destined to another, which portion of the packet does it replace?
- A. Layer 2 frame header and trailer
- B. Layer 3 IP address
- C. Layer 5 session
- D. Layer 4 protocol
Answer: Option A.
Explanation:
What does a router do with a packet received from one network and destined for another network? The router performs the following three major steps:
De-encapsulates the Layer 3 packet by removing the Layer 2 frame header and trailer.
Step 1.
Examines the destination IP address of the IP packet to find the best path in the routing table.
Step 2.
If the router finds a path to the destination, it encapsulates the Layer 3 packet into a new Layer 2 frame and forwards the frame out the exit interface.
Step 3.
Reference:
http://www.ciscopress.com/articles/article.asp?p=2180208&seqNum=8
