1. What port does the RIP protocol use?
RIP uses UDP port 520
2. What metric is used by the RIP protocol? How to use a metric to represent an unreachable network?
The metric for RIP is the number of hops . The number of hops for an unreachable network is 16 , and RIP treats it as an infinite distance.
3. What is the update cycle of the RIP protocol?
Decreasing a small random variable every 30s , RIP periodically sends updates . This prevents synchronization of updates with neighbors .
4. How many updates must be ignored before a route is marked unreachable?
If six updates are not received, a routing table entry will be marked as unreachable .
5. What is the purpose of the garbage collection timer?
When a route is declared unreachable, a garbage collection timer, or flush timer, is started. When the timer expires, the route is removed from the routing table. This process keeps an unreachable route in the routing table long enough for neighbors to be notified .
6. Why use a random timer to trigger an update? What is the size range of this timer?
Random timer, timing range 1~5s, to prevent triggering update "storms" when topology changes .
7. What are the differences between the request information and the response information of the RIP protocol?
The request message is used to send an update to the neighbor router , and the response message is used to transmit the routing update .
8. Which two types of request information are used by the RIP protocol?
A request message may request a complete update , or in some special cases, it may request a specific route .
9. Under what circumstances will a RIP protocol response message be sent?
Send a response message when the update timer expires, or when a request message is received.
10. Why does the RIP protocol block subnets at the boundary of the main network?
RIP updates do not include the subnet mask of the destination address , so the RIP router relies on the subnet mask of its own interface to determine how the primary network address is subnetted . If you do not configure a specific primary network address, the router will not know that the primary network is subnetted; therefore, the subnet of the primary network address will not be advertised to other primary networks.