- How many updates must be missed before a route entry will be marked as unreachable?
Answer: A route entry is marked as unreachable if six updates are missed.
- What is the purpose of the garbage collection timer?
Answer: 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.
- Why is a random timer associated with triggered updates? What is the range of this timer?
Answer: The random timer, whose range is 1 to 5 seconds, prevents a “storm” of triggered updates during a topology change.
- What is the difference between a RIP Request message and a RIP Response message?
Answer: A Request message asks a router for an update. A Response message is an update.
- Which two types of Request messages does RIP use?
Answer: A Request message may either ask for a full update or in some special cases it may ask for specific routes.
- Under what circumstances will a RIP response be sent?
Answer: A Response is sent when the update timer expires, or upon reception of a Request message.
- Why does RIP hide subnets at major network boundaries?
Answer: 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.
- Which UDP port number is used to access IGRP?
Answer: IGRP does not use a UDP port. It is accessed directly from the network layer, as protocol number 9.
- What is the maximum IGRP internetwork diameter, in hops?
Answer: The maximum IGRP network diameter is 255 hops.
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