SEMESTER 2 Chapter 9
EIGRP
V 4.0
9.0.1 / What features are found in EIGRP that are not found in other distance vector routing protocols? / Reliable Transport Protocol (RTP)Bounded Updates
Diffusing Update Algorithm (DUAL)
Establishing Adjacencies
Neighbor and Topology Tables
What type of protocol does EIGRP act like? / Link-state
What type of routing protocol is EIGRP? / Distance Vector
How is EIGRP similar to RIP v2? / EIGRP can operate with classful or classless routing behavior
9.1.1 / What protocol was the precursor to EIGRP? / IGRP
What are the metrics composed of? / bandwidth, delay, reliability, and load
What algorithm was used in IGRP? / the Bellman-Ford algorithm
What two things does EIDRP not do? / EIGRP does not send periodic updates and route entries do not age out.
What table does EIGRP maintain that is separate from the routing table? / Topology table
What is included in the above table? / includes both the best path to a destination network and any backup paths that DUAL has determined to be loop-free
Define loop-free. / the neighbor does not have a route to the destination network that passes through this router
What is the result of using mechanisms to prevent routing loops and count to infinity problems in RIP and IGRP? / Slow convergence
What does EIGRP use to solve these problems? / loop-free paths are achieved through a system of route calculations (diffusing computations) that are performed in a coordinated fashion among the routers
9.1.2 / What are the three type/length/value types in EIGRP? / EIGRP Parameters, IP Internal Routes, and IP External Routes
What is the protocol field value for EIGRP? / 88
What is the destination ip address? / 224.0.0.10
What is the MAC address for an EIGRP packet in a frame? / 01-00-5E-00-00-0A
9.1.2.2 / What are the four Opcodes for EIGRP? / EIGRP Parameters, IP Internal Routes, and IP External Routes
What are the two factors that EIGRP weights? / Bandwidth and delay
Define delay. / the sum of delays from source to destination in units of 10 microseconds
Define Bandwidth. / the lowest configured bandwidth of any interface along the route
What is the minimum length for a subnet mask in EIGRP? / 24
What is added to the subnet mask to reach the minimum length? / Zeros
9.1.3 / What are the three protocols does EIGRP support? / IP, IPX, and AppleTalk
What does EIGRP use to be able to support these protocols? / protocol-dependent modules (PDM)
9.1.4 / What protocol does EIGRP use to deliver and receive packets? / used by EIGRP for the delivery and reception of EIGRP packets
Why does EIGRP have to use the above protocol? / EIGRP was designed as a Network layer independent routing protocol; therefore, it cannot use the services of UDP or TCP because IPX and Appletalk do not use protocols from the TCP/IP protocol suite.
What are the two methods of delivery for RTP? / reliable delivery and unreliable delivery
What is the difference between the two methods of delivery? / Reliable requires acknowledgement of the packet
Unreliable does not require acknowledgement
What are the two methods that RTP can send packets? / Multicast and unicast
9.1.4.2 / What are Hello packets used for? / used by EIGRP to discover neighbors and to form adjacencies with those neighbors
What are Update packets used for? / used by EIGRP to propagate routing information
When are Update packets sent? / Only when necessary
What are ACK packets used for? / sent by EIGRP when reliable delivery is used
When are ACK packets used in EIGRP? / for EIGRP update, query, and reply packets
What type of delivery method does an ACK packet use? / Unreliable delivery
What are QUERY and REPLY packets used for? / used by DUAL when searching for networks and other tasks
9.1.5 / What must happen before EIGRP can exchange packets between routers? / EIGRP must first discover its neighbors
What is a Hello packet used for? / EIGRP routers discover neighbors and establish adjacencies with neighbor routers using the Hello packet
How often are hello packets sent? / Every 5 seconds
How often are hellos packets sent on multipoint nonbroadcast multiaccess networks (NBMA)? / Every 60 seconds
What does an EIGERP router assume if it continues to receive hello packets from a neighbor? / the neighbor and its routes remain viable
Define Holdtime. / the maximum time the router should wait to receive the next Hello before declaring that neighbor as unreachable
What is the holdtime by default? / 3 time the hello interval
What happens if the holdtime expires? / EIGRP will declare the route as down and DUAL will search for a new path by sending out queries
9.1.6 / Define partial. / the update only includes information about the route changes
Define bounded. / the propagation of partial updates sent only to those routers that are affected by the change
Why does EIGRP use partial bounded updates? / To conserve bandwidth
9.1.7 / What is the Diffusing Update Algorithm (DUAL)? / the convergence algorithm used by EIGRP
What problem is associated with DUAL recalculations? / Processor intensive
What does DUAL do to avoid recalculations? / DUAL maintains a list of backup routes it has already determined to be loop-free.
9.1.8 / Define Administrative Distance. / the trustworthiness (or preference) of the route source
What are the two default administrative distances for EIGRP? / 90 for internal routes
170 for external routes
What is the administrative distance for a summary route? / 5
9.1.9 / Can EIGRP be configured to use authentication? / Yes
9.2.2 / Define an Autonomous System. / autonomous system (AS) is a collection of networks under the administrative control of a single entity that presents a common routing policy to the Internet
Who is responsible for assigning AS? / Internet Assigned Numbers Authority (IANA)
What is the length of an AS number? / 32-bits
Who needs an autonomous system number? / Usually ISPs (Internet Service Providers), Internet backbone providers, and large institutions connecting to other entities that also have an AS number.
9.2.2.2 / What does EIGRP use a process ID for? / to represent an instance of their respective routing protocol running on the router
9.2.3 / What is the command to enable EIGRP as the routing protocol? / eigrp autonomous-system
Who chooses the autonomous system number used in the above command? / System administrator
What is the range available for autonomous system numbers? / 1 and 65535
9.2.4 / What are the two functions that the network command provides? / Any interface on this router that matches the network address in the network command will be enabled to send and receive EIGRP updates.
This network (or subnet) will be included in EIGRP routing updates.
9.2.4.2 / What is used in EIGRP to limit the number of interfaces within a network that will be advertised? / Wildcard mask
What is the inverse of a subnet called? / Wildcard mask
9.2.5 / What must be established before any updates can be sent or received? / Adjacencies
Define the following entries in the EIGRP neighbor table:
H column / Lists the neighbors in the order they were learned.
Address / The IP address of the neighbor.
Interface / The local interface on which this Hello packet was received.
Hold / The current hold time. Whenever a Hello packet is received, this value is reset to the maximum hold time for that interface and then counts down to zero. If zero is reached, the neighbor is considered "down".
Uptime / Amount of time since this neighbor was added to the neighbor table.
SRTT / Smooth Round Trip Timer) and RTO (Retransmit Interval) - Used by RTP to manage reliable EIGRP packets. SRTT and RTO are discussed further in CCNP courses.
Queue Count / Should always be zero. If more than zero, then EIGRP packets are waiting to be sent. Queue count is discussed further in CCNP courses.
Sequence Number / Used to track updates, queries, and reply packets. Sequence numbers are discussed further in CCNP courses.
If a ping is successful but the router still does not see the other router as a neighbor, what else should be checked? / Are both routers configured with the same EIGRP process ID?
Is the directly connected network included in the EIGRP network statements?
Is the passive-interface command configured to prevent EIGRP Hello packets on the interface?
9.2.6 / What is the command to disable automatic route summarization? / no auto-summary
What variably subnetted mean? / Use different subnet masks for subnets
9.2.6.2 / What happens if a packet matches the parent route but none of the child routes? / It is discarded
What are the two conditions that must be met for EIGRP to include a null0 summary route? / There is at least one subnet that was learned via EIGRP.
Automatic summarization is enabled.
What happens to the summary route when the no auto-summary command is issued? / It is removed
9.3.1 / What are the metrics that EIGRP can use? / Bandwidth
Delay
Reliability
Load
What two metrics are used by default? / Bandwidth
Delay
9.3.1.2 / What command can be issued to see the K values? / Show ip protocols
9.3.2 / What command can be used to examine the actual values used for bandwidth, delay, reliability, and load in the computation of the routing metric? / show interface
9.3.2.2 / Define delay. / a measure of the time it takes for a packet to traverse a route
9.3.2.3 / Define reliability. / a measure of the probability that the link will fail or how often the link has experienced errors
Define load. / the amount of traffic utilizing the link
9.3.3 / Does the bandwidth command change the actual speed of the interface? / no
9.3.4 / What is the multiplier used to calculate EIGRP metric? / 256
9.3.4.2 / What bandwidth is used in calculating the EIGRP value between two interfaces? / The slowest
What is the reference value for bandwidth in EIGRP? / 10,000,000
How is delay calculated in EIGRP? / EIGRP uses the cumulative sum of delay metrics of all of the outgoing interfaces.
How is the final metric that EIGRP uses calculated? / Add the bandwidth and delay metric calculations together
9.4.1 / What is the algorithm EIGRP uses to determine the best path? / DUAL (Diffusing Update Algorithm)
What are the four main features that DUAL provides? / Loop-free paths
Loop-free backup paths which can be used immediately
Fast convergence
Minimum bandwidth usage with bounded updates
What are the terms associated with DUAL? / Successor
Feasible Distance (FD)
Feasible Successor (FS)
Reported Distance (RD) or Advertised Distance (AD)
Feasible Condition or Feasibility Condition (FC)
9.4.2 / Define successor. / a neighboring router that is used for packet forwarding and is the least-cost route to the destination network
Define feasible distance(FD). / the lowest calculated metric to reach the destination network
9.4.3 / Define feasible successor(FS). / a neighbor who has a loop-free backup path to the same network as the successor by satisfying the feasibility condition
Define feasibility condition (FC). / when a neighbor's reported distance (RD) to a network is less than the local router's feasible distance to the same destination network
Define Reported Distance (RD) or Advertised Distance (AD) / an EIGRP neighbor's feasible distance to the same destination network.
9.4.4 / Where are the successor, feasible distance, and any feasible successors with their reported distances kept by a router? / EIGRP topology table or topology database
What command will show you the topology database? / show ip eigrp topology
9.4.4.2 / Know each piece of the topology table.
9.4.6 / What is the centerpiece of EIGRP is DUAL and its EIGRP route-calculation engine called? / FiniteState Machine (FSM)
What does the FSM define? / a set of possible states that something can go through, what events cause those states, and what events result from those states
9.4.6.2 / What happens after the interface is shut down? / DUAL searches for and then install a new route in the routing table
9.4.6.3 / What state does DUAL place a route in if the successor goes down and there is no feasible successor? / Active
What happens if the sender does not receive replies that have a route to the network? / It will not have a route to the network.
9.5.1 / What happens if a packet matches the parent route but not any of the child routes? / It is dropped
What happens is you disable auto summarization? / The null0 routes are removed
9.5.1.2 / What happens to all adjacencies after the no auto-summary command is issued? / All adjacencies are removed and recalculated
9.5.3 / What command is used to enter a manual route summarization? / Router(config-if)#ip summary-address eigrp as-number network-address subnet-mask
What happens to the routing table after the above command is entered? / A summary route is listed instead of the individual subnets
9.5.4 / What type of route can be used with any of the routing protocols we have used so far? / The "quad zero" static default route
What command is used to include a static default route with its EIGRP routing updates? / redistribute static
What does a default route provide a default path to? / outside the routing domain
9.5.5 / What can be changed to improve EIGRP? / Bandwidth utilization
9.5.5.2 / What are the two areas discussed that can also be fine tuned? / Hello intervals and hold times
What happens if the hold time is not adjusted when the hello interval is adjusted? / The neighbor adjacency will go down before the next hello interval expires
What should the hold time be set to? / 3 times the hello interval