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52 Cards in this Set
- Front
- Back
EIGRP |
Enhanced Interior Gateway Routing Protocol |
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Advertised Distance |
is an arbitrary numerical value assigned to a routing protocol, a static route or a directly-connected route based on its perceived quality of routing. |
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How is EIGRP Calculated |
1. Bandwidth 2. Delay 3. Load 4. Reliability |
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Feasible distance (FD) |
the metric of the best route to reach a network. That route will be listed in the routing table. |
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Reported distance (RD) |
the metric advertised by a neighboring router for a specific route. It other words, it is the metric of the route used by the neighboring router to reach the network. |
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Successor |
is the route with the best metric (Best Path) to reach a destination. That route is stored in the routing table. |
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A feasible successor |
is a backup path to reach that same destination that can be used immediately if the successor route fails. |
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Variance Command |
The variance is a multiplier. So what ever the metric is for your successor you multiply that by the variance and what ever feasible successors fall into that range will be used for load balancing. |
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Neighbor Discovery/Recovery |
Neighbor Discovery/Recovery is the process that routers use to dynamically learn of other routers on their directly attached networks |
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Adjacency |
A neighbor relationship |
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RTP |
Reliable Transport Protocol
provides sequencing and acknowledgment for EIGRP packets between neighbors. |
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multi-access network |
A flexible system by which every station can have access to the network at all times; provisions are made for times when two computers decide to transmit at the same time. http://www.commodore.ca/manuals/128_system_guide/glossary.htm |
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Hello Packets |
are used for neighbor discovery. As soon as you send hello packets and receive them your EIGRP routers will try to form the neighbor adjacency. |
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Query |
Packets have routing information and are sent reliable to whatever router that requires the information. Update packets can be sent to a single neighbor using unicast or to a group of neighbors using multi-cast |
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Reply |
Packets are used in response to the query packets and are reliable |
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ACK packets |
are used to acknowledge the receipt of update, query and replay packets. Ack packets are sent by using unicast |
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Neighbor Table |
This is where EIGRP stores all information of directly connected neighbors. |
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EIGRP Topology Table |
this is the information routers exchange after routers have become neighbors |
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The command to start eigrp using AS (autonomous system) number 1 |
router eigrp 1 |
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Why is "no auto summary" needed? |
by default EIGRP will behave like a classful routing protocol which means it won't advertise the subnet mask along the routing information. |
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Passive Interface Command |
Advertise a network without sending EIGRP packets on the interface and forming EIGRP neighbors |
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passive-interface default |
If you have a configuration with 50+ interfaces you probably don't want to type this command on each of those interfaces. You can configure passive-interface default and only activate the interfaces you want to run EIGRP on |
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Show ip protocols |
it will show you 1. What networks you are routing 2. Passive Interfaces 3. Administrative Distance |
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H (Handle) |
the order when the neighbor adjacency was established. your first neighbor will have a value of 0, the second 1, and so on |
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Hold Uptime (sec) |
this is the holddown timer per EIGRP protocol.
NOTE: once this timer expires we will drop the neighbor adjacency. The default holddown timer is 15 seconds.
On older IOS versions only a hello packet would reset the holddown timer but on newer IOS versions any EIGRP packet after the first hello will reset the holddown timer. |
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Holddown Timer |
works by having each router start a timer when they first receive information about a network that is unreachable. Until the timer expires, the router will discard any subsequent route messages that indicate the route is in fact reachable. |
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SRTT |
Smooth round-trip time
The number of miliseconds it takes to send an EIGRP packet to you neighbor and receive an acknowledgment packet back |
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RTO |
Retransmission Timeout
The amount of time in miliseconds that EIGRP will wait before retransmitting a packet from the retransmission queue to this neighbor |
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Q Cnt |
Q Count
The number of EIGRP packets (update, Query or Reply) in the queue that are awaiting transmission. Ideally you want this number to be 0 otherwise it might be an indication of congestion on the network. |
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Seq Num |
Sequence Number
This will show you the sequence number of the last update, query or reply packet that you received from your EIGRP neighbor |
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Passive |
Passive is good.
we like routing information to be passive which means that we have learned information about a network and there are no changes in the topology table. |
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Active |
Active is not good.
It means we have lost information about a certain network and EIGRP doesn't know another way of reaching this network. It will go into active mode and send query packets to ALL its neighbors asking them if they know how to reach this network. |
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Reply Status |
EIGRP will track all the query packets it has sent to neighbors since you need a reply in return. By setting the reply status flag it will do this |
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Sia Status |
Stuck in Active
This is bad
It means that EIGRP has not received a reply to q query packet from one of the neighbors within the allowed time (about 3 minutes). When this happens EIGRP will drop neighbor adjacency and it will be stuck in active. |
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What does the P stand for in
P 2.2.2.0/24 |
Passive |
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Feasible Distance |
Total Distance |
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Which number is the feasible distance?
(156160/128256) |
156160 |
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Advertised Distance |
This is the where your EIGRP neighbor reports how far it is for him to reach the network |
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Which number is the administrative distance?
(156160/128256) |
128256 |
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What is the letter D in the routing table? |
Dual or diffusing update algorithm |
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What is Dual? |
This is the algorithm behind EIGRP which is why we find the D listed in the routing table.
NOTE: We do not use E because that is used for Exterior gateway protocol. |
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In the statement
2.2.2.0 [90//156160]
What is the feasible distance? |
156160 |
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What command do you use to show k values? |
Show ip protocols |
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How can you change the bandwidth Static Value? |
Bandwidth Command
NOTE: this does not change the actual value of the command |
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When EIGRP has to choose from two routes; will it choose the route with the lower or higher bandwidth? |
Lower |
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Can you use the delay command to change a value influencing EIGRP? |
Yes
NOTE: It does not actually change the delay for the interface but can be used to influence routing protocols |
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Is MTU used in the metric calculation for EIGRP? |
Maximum Transmission Unit
This is being exchanged between EIGRP neighbors but is not used for metric calculation |
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What is the EIGRP Formula? |
Metric = bandwidth (slowest link) + delay (sum of delays) |
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What is the bandwith calculation? |
(10 ^7 / minimum bandwidth in the path) * 256 |
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What is the calculation for delay? |
sums of delays in the path multiplied by 256 (in tens of microseconds) |
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Why do we use 256 when multiplying with EIGRP? |
So it is compatible with IGRP |
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What is the bandwidth for a T1 interface? |
1.544 Mbit |