Chapter 5

1:
A:	RIP uses UDP port 520.
2:
A:	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:
A:	RIP sends periodic updates every 30 seconds minus a small random variable to prevent the updates of neighboring routers from becoming synchronized.
4:
A:	A route entry is marked as unreachable if six updates are missed.
5:
A:	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.
6:
A:	The random timer, whose range is 1 to 5 seconds, prevents a " storm " of triggered updates during a topology change.
7:
A:	A Request message asks a router for an update. A Response message is an update.
8:
A:	A Request message may either ask for a full update or in some special cases it may ask for specific routes.
9:
A:	A Response is sent when the update timer expires, or upon reception of a Request message.
10:
A:	RIP updates do not include the subnet mask of the destination address, so a RIP router depends on the subnet masks of its own interfaces to determine how an attached major network address is subnetted. If a router does not have an attachment to a particular major network address, it has no way to know how that major network is subnetted . Therefore, no subnets of a major network address can be advertised into another major network.