The second branch in the local computation logic causes the EIGRP router to ask its neighbors about their current best route to a subnet, hoping to find an available, loop-free alternative route to that subnet. When no FS route is found, the EIGRP router goes active for the route. Going active is jargon for the process of changing a route’s status to active. Once the router is active, EIGRP multicasts Query messages to its neighbors, asking the neighbors if they have a vali..
Summarization hides details in order to simplify the routing process. One of the keys to scalable routing is to take large complicated sets of advertisements and reduce them as much as possible. Summarization reduces router resource consumption (CPU and memory) required to store and process routes by reducing the number of routes. Summarization also saves network capacity, because fewer advertisements are required and each advertisement is smaller. Summarization also hi..
Multicast Forwarding Using Sparse Mode
A dense-mode routing protocol is useful when a multicast application is so popular that you need to deliver the group traffic to almost all the subnets of a network. However, if the group users are located on a few subnets, a dense-mode routing protocol will still flood the traffic in the entire internetwork, wasting bandwidth and resources of routers. In those cases, a sparse-mode routing protocol, such as PIM-SM, could be used to help reduce waste of network resources. The ..
RSVP is a per-flow protocol that requests a bandwidth reservation from every node in the path of the flow. In its simplest form, RSVP is a unidirectional protocol, so if a bidirectional reservation is required for a flow, both endpoints must initiate a request for a reservation. Basic RSVP protocol operation is shown in Figure 8-1 and its configuration in Example 8-1. The endpoints, or other network devices on behalf of the endpoints, send unicast signaling messages to estab..
Synchronizing the Time on All Routers (NTP)
Network Time Protocol (NTP) is an open standard protocol for time synchronization. You can implement NTP on a router to provide automatic and efficient time synchronization. To enable a basic NTP configuration, enter the following commands: Router#configure terminal Enter configuration commands, one per line. End with CNTL/Z. Router(config)#clock timezone EST -5 Router(config)#clock summer-time EDT recurring Router(config)#ntp server 172.25.1.1 Router(config)#end Rou..
