The Longest Match Routing Rule
Routing to any destination is always done on a longest match basis: A router that has to decide between two different length prefixes of the same network will always follow the longer mask. Suppose, for example, that a router has the following two entries in its routing table: 198.32.1.0/24 via path 1 198.32.0.0/16 via path 2 When attempting to deliver traffic to host 192.32.1.1, the router tries to match the destination that has the longest prefix and will deliver the traff..
Classful Routing: Summarization at Boundary Routers
A question arises from the preceding discussion: How does a RIP process interpret the subnet of a major network if it has no interfaces attached to that network? Without an interface on the class A, B, or C network of the destination, the router has no way of knowing the correct subnet mask to use and therefore no way of correctly identifying the subnet. The solution is simple: If a router has no direct attachments to the network, then it needs only ..
The Cisco VPN Client for Windows supports two interfaces: CLI and GUI. This book will focus on the GUI interface of the 4.6 client. Once you have installed the client, go to Start > Programs > Cisco VPN Software Client > VPN Client to access the GUI. Sometimes the application is referred to as the "VPN Dialer," after the older 3.x application name. Operating Modes The VPN Client has two operating modes: • Simple Mode, shown in Figure 12-1 Figu..
When an OSPF network grows beyond a single area, you need to be aware of the role played by each OSPF router in a topology. Specifically, four OSPF router types exist: ■ Internal router: All the networks directly connected to an internal router belong to the same OSPF area. Therefore, an internal router has a single link-state database. ■ Area border router (ABR): An ABR connects to more than one OSPF area and therefore maintains multiple link-state databases (one for e..
For this example, we will take a relatively simple view that the PE router will trust the CE router's DSCP/IP Precedence settings and map them to the MPLS EXP traffic priority field in a simple way. So we will focus on the configuration required on the PE and P routers to make use of this information. First, the PE routers have the dual function of converting DSCP or IP Precedence values to MPLS EXP values and then using this information appropriately when forwarding the pac..
