Bởi vì điều này, nó được gọi là một giao thức không đáng tin cậy. Điều này không có nghĩa là UDP là không hiệu quả, chỉ là nó không xử lý các vấn đề về độ tin cậy. Hơn nữa, UDP không tạo ra một mạch ảo, cũng không liên hệ với điểm đến trước khi cung cấp thông tin cho nó | Routing Information Protocol RIP 263 RIP Timers RIP uses three different kinds of timers to regulate its performance Route update timer Sets the interval typically 30 seconds between periodic routing updates in which the router sends a complete copy of its routing table out to all neighbors. Route invalid timer Determines the length of time that must expire 90 seconds before a router determines that a route has become invalid. It will come to this conclusion if it hasn t heard any updates about a particular route for that period. When that happens the router will send out updates to all its neighbors letting them know that the route is invalid. Route flush timer Sets the time between a route becoming invalid and its removal from the routing table 240 seconds . Before it is removed from the table the router notifies its neighbors of that route s impending doom. The value of the route invalid timer must be less than that of the route flush timer. This is to provide the router with enough time to tell its neighbors about the invalid route before the routing table is updated. Configuring RIP Routing To configure RIP routing just turn on the protocol with the router rip command and tell the RIP routing protocol which networks to advertise. That s it. As an example let s configure our four-router internetwork with RIP routing. 2621A RIP has an administrative distance of 120. Static routes have an administrative distance of 1 by default and since you currently have static routes configured the routing tables won t be propagated with RIP information. The first thing you need to do is to delete the static routes off each router. This is done with the no ip route command. Notice that in the 2621A router output below you must type the whole ip route command to delete the entry. 2621A config t Enter configuration commands one per line. End with CNTL Z. 2621A config no ip route Copyright 2000 SYBEX Inc. Alameda CA 264 Chapter
