Summary of Rules for Routes Advertised in BGP Updates
The following list summarizes the rules dictating which routes a BGP router sends in its Update messages: ■ Send only the best route listed in the BGP table. ■ To iBGP neighbors, do not advertise paths learned from other iBGP neighbors. ■ To eBGP neighbors, do not advertise paths for which the neighbor’s AS is already in the AS_PATH PA. ■ Do not advertise suppressed or dampened routes. ■ Do not advertise routes filtered via configuration. The first two rules..
Finding an Alternative Path to a Remote Network
When the path to a network is lost, EIGRP goes to a lot of trouble to find an alternative path. The method that EIGRP uses to find alternative paths is very reliable and very fast. The following list describes the process after a neighbor goes offline: 1. The router marks the routes that were reached by sending the traffic to that neighbor. 2. The router looks in the topology table, which has every advertisement received, to determine whether there is an alterna..
The point-to-point model is the most robust of the four models—each PVC is treated as a point- to-point subinterface. Therefore, losing a single PVC does not cause loss of connectivity. Instead, each point-to-point subinterface is a separate subnet. Each PVC can have different costs, according to the CIR. Point-to-point has faster convergence than any other model and allows for partial mesh. The point-to-point model has a serious problem with flooding, however..
You can see from the previous discussion that, although this technique is efficient, it has drawbacks, such as scalability problems. These problems do not affect the enterprise customer because the networks are not changed rapidly and frequently, and because they do not carry very large routing tables. Demand caching is a scalable method for the enterprise environment because packet flow is not very dynamic. Cache deletion frees space in the memory as well. ISPs..
A variable-length subnet mask (VLSM) is designed to allow greater use of IP address space by borrowing bits from the subnet mask and allocating them to host devices. To allow a greater number of devices to connect to the Internet and intranets, the standards bodies of various routing protocols designed an IP routing algorithm to cater to IP networks with a different subnet mask than the default used in classful networks. Note Routing algorithms that support VLSM are as foll..
