Host and Router Subnet Mask Mismatch Example

In classful IP networks, every router and host in the same major network should share a common subnet mask. If there are disagreements on the length of the subnet mask, packets are not routed correctly.

Table 7-10 shows how a UNIX host and a router will interpret an IP address differently if they have different subnet masks specified for the same major network.

Table 7-10 Host and Router Subnet Mask Mismatch Example

Routing Information

Host Value

Router Value

Destination IP address

Subnet mask

Interpreted address

Subnet address 48, host 1

Subnet address 32, host 17

The host interprets the IP address as being Host 1 on the third subnet (subnet address 48). However, because it is using a different subnet mask, the router interprets the address as being Host 17 on the first subnet (subnet address 32). Depending on the network topology and the router configuration, packets destined for IP address might be sent to the wrong destination host, sent from the wrong interface, or dropped altogether.

Was this article helpful?

0 0
The Ultimate Computer Repair Guide

The Ultimate Computer Repair Guide

Read how to maintain and repair any desktop and laptop computer. This Ebook has articles with photos and videos that show detailed step by step pc repair and maintenance procedures. There are many links to online videos that explain how you can build, maintain, speed up, clean, and repair your computer yourself. Put the money that you were going to pay the PC Tech in your own pocket.

Get My Free Ebook

Post a comment