If the source is 192.168.1.254 and the destination is 10.1.1.254, the given paths could be

If the source is 192.168.1.254 and the destination is 10.1.1.254, the given paths could be:

192.168.0.0/24
10.1.0.0/16
192.168.1.0/26
172.16.100.0/24
192.168.1.64/26
10.2.1.0/16
How does it travel?

The Correct Answer and Explanation is:

To determine how a packet travels from source IP 192.168.1.254 to destination IP 10.1.1.254, we need to analyze routing path selection using the Longest Prefix Match rule. This rule ensures the most specific (longest) match is selected when multiple routes are available.

Step 1: Check Matching Destination Networks

We are focusing on the destination IP 10.1.1.254, so we evaluate which of the provided network paths it falls into:

1. 192.168.0.0/24 – Doesn’t match (not relevant; source network)
2. 10.1.0.0/16 – Matches: 10.1.1.254 falls within 10.1.0.0 – 10.1.255.255
3. 192.168.1.0/26 – Doesn’t match (source network, not destination)
4. 172.16.100.0/24 – Doesn’t match
5. 192.168.1.64/26 – Doesn’t match
6. 10.2.1.0/16 – Doesn’t match

So, the only matching path for the destination IP is:

✅ 10.1.0.0/16

Step 2: Apply Longest Prefix Match

If multiple paths match, the router chooses the one with the longest subnet mask (i.e., the most specific route). But here, only one path (10.1.0.0/16) matches the destination, so that is the route used.

✅ Correct Answer: 10.1.0.0/16

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📝 Explanation

In IP routing, when a packet is transmitted from a source to a destination, routers determine the best path based on routing tables using a principle called Longest Prefix Match. This means that if several routes match the destination IP, the one with the most specific (longest) subnet mask is chosen.

Given the source IP is 192.168.1.254 and the destination is 10.1.1.254, we inspect the list of potential network paths to find which one contains the destination IP. Among the given options, only the 10.1.0.0/16 network includes the destination IP. A /16 subnet includes IPs from 10.1.0.0 to 10.1.255.255, and 10.1.1.254 falls within this range.

Other networks either belong to the source IP range (like 192.168.1.0/26 or 192.168.1.64/26) or to unrelated IP ranges (like 10.2.1.0/16 or 172.16.100.0/24). Since 10.1.0.0/16 is the only matching route, it is selected.

If multiple matches existed (e.g., both /16 and /24 networks covering the destination IP), the one with the longer prefix (e.g., /24) would be chosen. This ensures efficient and accurate routing of packets through the most specific path available.

Thus, the packet from 192.168.1.254 to 10.1.1.254 travels via 10.1.0.0/16.