O'Reilly logo

IP Routing Primer by Robert Wright

Stay ahead with the world's most comprehensive technology and business learning platform.

With Safari, you learn the way you learn best. Get unlimited access to videos, live online training, learning paths, books, tutorials, and more.

Start Free Trial

No credit card required

Understanding VLSM

This section provides scenarios on using VLSM and indicates the issues it can cause. Remember that VLSM refers to using different masks on the same major net. In Figure 4-6, the major net of 168.71.0.0 has two different masks— 255.255.255.0 and 255.255.255.252.

Figure 4-6. 168.71.0.0 has two masks.

VLSM Using RIP and IGRP

In general, RIP V1 and IGRP do not support VLSM because they do not include the subnet masks associated with routes in their routing advertisements. This forces routers to derive the correct masks from the interfaces the routes are received over. Using different masks creates the mask ambiguity problem ...

With Safari, you learn the way you learn best. Get unlimited access to videos, live online training, learning paths, books, interactive tutorials, and more.

Start Free Trial

No credit card required