Term
| What are some of the key characteristics of RIPv1 and 2? |
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Definition
| Hop count is used as the metric for path selection if the Hop count is greater than 15 RIP cannot supply a route. Routing updates are broadcast or multicast every 30 seconds. |
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Term
| What are the key characteristics of EIGRP? |
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Definition
-Unequal cost load balancing
-Uses DUAL to calcualte the shortest path
-Routing updates are sent only when there is a change in the topology. |
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Term
| How are distance vector routes advertised? |
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Definition
| As vectors of distance and direction. |
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Term
| Does a router in a distance vector network have complete knowledge of the entire path to a destination network? |
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Definition
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Term
| What are the 2 pieces of information that a distance vector router knows? |
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Definition
-the direction or interface in which packets should be forwarded.
-The distance or how far it is to the destination network. |
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Term
| What are the two reasons why sending an entire routing table in an update is inefficient? |
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Definition
| This method is inefficient because the updates not only consume bandwidth, but also consume router CPU resources to process the updates. |
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Term
| What is the periodic update time for RIP? |
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Definition
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Term
| What is the periodic update time for IGRP? |
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Definition
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Term
| What is the IP and MAC address for broadcast updates? |
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Definition
-255.255.255.255
-FF:FF:FF:FF:FF:FF |
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Term
| What is the algorithm used for? |
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Definition
| To calculate the best paths and then send that info to the neighbors. |
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Term
| What process does the routing protocol define? |
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Definition
-Sending & receiving routing info
-Calculating the best paths and installing routes in the routing table.
-detecting and reacting to topology changes. |
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Term
| Define Time to Convergence? |
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Definition
| How quickly the routers in the network topology share routing info. |
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Term
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Definition
| Defines how large a network can become based on the routing protocol. |
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Term
| Define Classless or Classful |
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Definition
-Classless routing protocols include the subne mask in the updates.
-Classful routing protocols do not include the subnet mask and cannot support VLSM. |
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Term
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Definition
| Includes the requirements of a routing protocol such as memory space, CPU utilization,and bandwidth link utilization. |
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Term
| Define implementation and Maintenance |
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Definition
| Describes the level of knowledge that is required for a network admin to implement and maintain the network based on the routing protocol deployed. |
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Term
| List some advantages for distance vector protocols. |
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Definition
-Simple implementation & maintenance
-Low resource requirements |
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Term
| List some disadvantages for distance vector protocols. |
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Definition
-Slow convergence
-Limited scalability
-Routing loops |
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Term
| Immediately after booting, what routes are initially discovered? |
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Definition
| Directly connected networks |
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Term
| After completing the initial route discovery, what does the routerstart to do? |
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Definition
| Initially discovers their own directly connected networks and subnet masks. This information is added to their routing tables. |
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Term
| What does the initial exchange of routing information contain? |
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Definition
| Includes info about their directly connected networks. |
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Term
| What does the router do with the information that is not contained in its routing table? |
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Definition
| Any routes that are not currently in its routing are added. |
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Term
| After the first exchange of routing updates, what has been added to each routing table? |
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Definition
| Each router knows about the connected networks of their directly connected neighbors. |
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Term
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Definition
| The state of a set of routers that have the same topological info about the internetwork in which they operate. |
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Term
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Definition
| Routing technique in which info about routes is prevented from exiting the router interface through which that information was received. Useful in preventing routing loops. |
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Term
| The amount of time it takes for a network to converge is directly proportional to what? |
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Definition
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Term
| The speed of achieving convergence consists of what two things? |
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Definition
-How quickly the routers propagate a change in the topology in a routing update to its neighbors.
-The speed of calculation best path routes using the new routing information collected. |
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Term
| What are the two reasons routers exchange routing updates? |
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Definition
-Exchange routing info with their neighbors
-Maintain up-to-date routing info in the routing table. |
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Term
| What are four reasons listed for topology changes? |
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Definition
-Failure of a link
-Intro of a new link
-Failure of a router
-Change of link parameters |
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Term
| What are three additional timers? |
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Definition
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Term
| If an update has not been received to refresh an existing route after 180 seconds, what happens to that route in the routing table? |
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Definition
| The route is marked as invalid by setting the metric to 16. |
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Term
| What happens to the route after 240 seconds have elapsed? |
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Definition
| When the flush timer expires, the route is removed from the routing table. |
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Term
| What does a holddown timer? |
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Definition
| The timer stabilizes routing info and helps prevent routing loops during periods when the topology is converging on new information. |
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Term
| What are the two commands that will show the timers? |
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Definition
R1#show ip route
R1#show ip protocols |
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Term
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Definition
| Updates are sent only to those routers that need the updated info. |
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Term
| What are characteristic of EIGRP updates? |
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Definition
-Non-periodic
-Partial updates
-Bounded |
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Term
| What is a triggered update? |
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Definition
| Is a routing table update that is sent immediately in response to a routing change. |
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Term
| What are three reasons to send a triggered update? |
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Definition
-An interface change state
-A route has entered(or exited)the unreachable state
-A route installed in the routing table |
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Term
| What are the two problems with triggered updates? |
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Definition
| Packets containing the update message can be dropped or corrupted by some link in the network. The triggered updates do not happen instantaneously. |
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Term
| What is it called when all the routers send updates at the same time on a network with a hub at the center? |
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Definition
| Synchronization of updates |
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Term
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Definition
| A condition in which a packet is continuously transmitted within a series of routers without ever reaching its intended destination. |
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Term
| What are some causes for routing loops? |
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Definition
-Incorrectly configured static routes
-Incorrectly configure route redistribution
-Inconsistent routing tables
-Incorrectly configured or installed discarded routes. |
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Term
| What mechanism is built into IP to overcome routing loops? |
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Definition
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Term
| What conditions can be created because of routing loops? |
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Definition
-Link bandwidth will be used for traffic looping back and forth between routers in a loop.
-A routers CPU will be strained due to looping packets. |
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Term
| What are some mechanisms use to avoid routing loops? |
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Definition
-Define maximum metric to prevent count to infinity
-Holddown timers
-Split Horizon
-Route poisoning or poison reverse |
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Term
| What is count to infinity? |
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Definition
| A condition that exists when inaccurate routing updates increase the metric value to infinity for a network that is no longer reachable. |
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Term
| What is infinity defined by? |
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Definition
| Setting a maximum metric value |
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Term
| What is infinity for RIP? |
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Definition
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Term
| What is it called when a route goes up, then down, then up etc? |
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Definition
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Term
| What are holddown timers? |
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Definition
| They are used to prevent regular update messages from inappropriately reinstating a route that may have gone bad. |
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Term
| What is split horizon rule? |
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Definition
| That a router should not advertise a network through the interface which the update came. |
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Term
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Definition
| It is used to mark the route as unreachable in a routing update that is sent to other routers. |
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Term
| What is split horizon with poison reverse? |
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Definition
| States when sending updates out a specific interface, designate any networks that were learned on that interface as unreachable. |
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Term
| What is time-to-live (TTL)? |
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Definition
| An 8-bit field in the IP header that limits the number of hops a packet can traverse through the network before it is discarded. |
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Term
| What happens when a packet's TTL reaches 0? |
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Definition
| The packet is discarded and the routes send an ICMP error message back to the source of the IP packet. |
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Term
| What are the factors that affect the distnace vector protocol? |
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Definition
-Size of the network
-Compatibility between models of routers
-Admin knowlege required |
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Term
| What are features of RIP? |
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Definition
-Split Horizon
-Split Horizon with poison reverse
-Load balancing six equal paths |
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Term
| What are the feature introduced with RIPv2? |
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Definition
-Subnet mask in routing updates
-Authentication mechanism
-Supports VLSM
-Manual route summary
-Uses multicast addresses |
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Term
| What are the features of EIGRP? |
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Definition
-Triggered updates
-Use of the topology table
-Supports VLSM
-Establishment of adjancies with neighboring rotuers. |
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Term
| What are advantages of EIGRP? |
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Definition
-Minimum bandwidth and cumulative delay of the path.
-Fast convergence
-Bounded updates
-Supports multiple layer protocols. |
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