AS_PATH Prepending and Route Aggregation
The concept and motivation behind the AS_PATH prepend feature is simple—impact the AS_PATH length decision step by increasing the length of the AS_PATH. To do so, a router simply configures a route map, refers to it with a neighbor route-map command, with the route map using the set as-path prepend asn1 asn2… command. As a result, the route map prepends additional ASNs to the AS_SEQUENCE. Any ASN can be prepended, but in practice, it makes the most sense to prepend the lo..
Label Switching in Frame-Mode MPLS
After receiving the Layer 2 PPP frame from the San Jose router, the San Francisco router immediately identifies the received packet as a labeled packet based on its PPP Protocol field value and performs a label lookup in its Label Forwarding Information Base (LFIB). NOTE LFIB also is called Tag Forwarding Information Base (TFIB) in older Cisco documentation.The LFIB entry corresponding to inbound label 30 (and displayed in Example C-2) directs the San Francisco router to rep..
Class-Based Shaping Configuration
Class-Based Shaping (CB Shaping) implements all the core concepts described so far in this hapter, plus several other important features. First, it allows for several Cisco IOS queuing ools to be applied to the packets delayed by the shaping process. At the same time, it allows or fancy queuing tools to be used on the interface software queues. It also allows for lassification of packets, so that some types of packets can be shaped at one rate, a second type f packet can be s..
There are many different ways to configure two routers to allow Token Ring to Token Ring bridging through DLSw. The most common reason for doing this is to allow Token Ring SNA LLC2 devices to communicate with a mainframe Front End Processor (FEP) attached to another Token Ring. It is relatively common to have many remote rings connecting to a single central ring. In cases like this, it is often best to use one or more dedicated DLSw routers at the central location. The CPU o..
With the emergence of voice traffic into data networks, the need to differentiate between the various classes of service has become greater. PQ/CBWFQ, most commonly known as LLQ, is a new feature that provides a strict priority queue for voice traffic and a weighted fair queue for each of the other classes of traffic. LLQ brings strict priority queuing to the CBWFQ scheme. Figure 18-4 illustrates the basic concepts of how LLQ works. Figure 18-4. How LLQ Works Without ..
