Routing Information Protocol Version 2

1: Which three fields are new to the RIPv2 message format?

*** The Route Tag field, the Subnet Mask field, and the Next Hop field are RIPv2 extensions that do not exist in RIPv1 messages. The basic format of the RIP message remains unchanged between the two versions; version 2 merely uses fields that are unused in version 1.

2: Besides the extensions defined by the three fields of question 1, what are the other two major changes from RIPv1?

***In addition to the functions that use the new fields, RIPv2 supports authentication and multicast updates.

3: What is the multicast address used by RIPv2? What is the advantage of multicasting messages over broadcasting them?

***RIPv2 uses the multicast address 224.0.0.9. Multicasting of routing messages is better than broadcasting because hosts and non-RIPv2 routers will ignore the multicast messages .

4: What is the purpose of the Route Tag field in the RIPv2 message?

*** When another routing protocol uses the RIPv2 domain as a transit domain, the protocol external to RIPv2 can use the Route Tag field to communicate information to its peers on the other side of the RIPv2 domain.

5: What is the purpose of the Next Hop field?

*** The Next Hop field is used to inform other routers of a next-hop address on the same multiaccess network that is metrically closer to the destination than the originating router.

6: What is the UDP port number used by RIPv2?

***RIPv2 uses the same UDP port number as RIPv1, port number 520.

7: Which one feature must a routing protocol have to be a classless routing protocol?

***A classless routing protocol does not consider the major network address in its route lookups, but just looks for the longest match.

8: Which one feature must a routing protocol have to use VLSM?

*** To support VLSM, a routing protocol must be able to include the subnet mask of each destination address in its updates.

9: Which two types of authentication are available with Cisco's RIPv2? Are they both defined in RFC 1723?

*** Cisco's implementation of RIPv2 supports clear-text authentication and MD5 authentication. Only clear-text authentication is defined in RFC 1723.

Routing Information Protocol

1:What port does RIP use?

* RIP uses UDP port 520.

2:What metric does RIP use? How is the metric used to indicate an unreachable network?

* RIP uses a hop count metric. An unreachable network is indicated by setting the hop count to 16, which RIP interprets as an infinite distance.

3:What is the update period for RIP?

* RIP sends periodic updates every 30 seconds minus a small random variable to prevent the updates of neighboring routers from becoming synchronized.

4:How many updates must be missed before a route entry will be marked as unreachable?

* A route entry is marked as unreachable if six updates are missed.

5:What is the purpose of the garbage collection timer?

* The garbage collection timer, or flush timer, is set when a route is declared unreachable. When the timer expires, the route is flushed from the route table. This process allows an unreachable route to remain in the routing table long enough for neighbors to be notified of its status.