Route Reflection Topology Models
National networks are usually laid out in concentration points across geographical regions. Providers have points of presence (POPs), sometimes called hubs, in different regions in the U.S. with high-speed links connecting different locations in a partial-mesh topology. The route reflector concept can be used to logically interconnect the routers running BGP in a pattern that follows the physical topology. Figure 9-5 illustrates a complex arrangement featuring route reflector..
Frame Relay and ATM Internet Access
Frame Relay and ATM (Asynchronous Transfer Mode) connections are among the most economical ways for corporations to connect to the Internet. Purchasing dedicated access connections with sufficient capacity can be prohibitively expensive for many companies, in which case they might consider connecting via existing Frame Relay or ATM services. With these alternative access methods, corporations can purchase enough bandwidth to meet their existing needs while providing a practic..
Once a PIM-SM router has joined a more efficient SPT, it may not need to receive multicast packets over the RPT any more. For example, when R4 in Figure 20-17 notices that it is receiving the group traffic over RPT and SPT, it can and should ask the RP to stop sending the traffic. To stop the RP from forwarding traffic to a downstream router on the shared tree, the downstream router sends a PIM-SM Prune message to the RP. The Prune message references the (S,G) SPT, which ide..
The current IEEE 802.11e draft describes an Enhanced Distributed Coordination Function (EDCF). EDCF is an enhancement of DCF, previously described. The main enhancement is the adjustment of variable CWmin and CWmax random backoff values based upon traffic classification. This feature is supported in current Cisco Aironet software. Figure 11-6 shows the principle behind different CWmin values per traffic classification. All traffic waits the same DIFS, but the CWmin value use..
Using the Cisco Discovery Protocol
CDP is enabled by default on the router, and on all interfaces. If you have previously disabled it, and you want to re-enable CDP on the router, you can issue the cdp run global configuration command: Router1(config)#cdp run This turns on CDP processing on all supported interfaces by default. If you don't want to run CDP on a particular interface, you can use the no cdp enable command, as we did for the serial interface in the example: Router1(config)#interface Serial0/0Route..
