EIGRP Flashcards

1
Q

Which type of authentication supports EIGRP?

A

Only supports MD5

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2
Q

What are the requirements to became EIGRP neighbor?

A
  • Must be able to send/receive IP packets
  • The primary IP address of the interface must be in the same subnet
  • AS number must be the same
  • Connected interface must not be passive
  • Authentication must pass
  • K-values used must match
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3
Q

Which information omits the “show ip eigrp interfaces” command?

A

It omits the passive interfaces

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4
Q

Which protocol shows the passive interfaces in EIGRP?

A

Show ip protocol

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5
Q

How can you manually change the EIGRP hello and hold intervals?

A

Ip hello-interval eigrp

Ip hold-time eigrp

Interval = seconds

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6
Q

What is the default time for hello and hold intervals in EIGRP?

A

LAN > hello: 5sec ; hold: 15sec

WAN > hello: 60sec ; hold: 180sec

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7
Q

Which command is used to see in EIGRP the K-values?

A

Show ip protocols

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8
Q

How can you change the K-values?

A

Metric weights 0 1 0 1 0 0

Where the 1st value is the tos that is always 0

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9
Q

How long does the router wait to act when no hello packets are received?

A

3x hello-interval. By default 15 seconda

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10
Q

What is the EIGRP multicast address in IPv4 to send hello?

A

224.0.0.10

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11
Q

Which device is affected by the change of the hello and hold timers?

A

Hello timer > local device

Hold timer > the neighbors

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12
Q

Which commands can you use to verify the hello and dead intervals in EIGRP?

A
  • show ip eigrp interface detail

* show ip eigrp neighbors (no muestra el tiempo exacto sino un contador)

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13
Q

What are the uses of DUAL?

A
  • Determine the best loop-free path
  • Determine the backup loop-free path
  • Provide fast convergence
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14
Q

What is the IP protocol number of EIGRP?

A

88

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15
Q

What type of protocol is EIGRP?

A

Distance vector

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16
Q

What are the 3 steps in EIGRP to provide network convergence?

A
  1. Neighbor relationship
  2. Topology exchange information
  3. DUAL to populate the routing table
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17
Q

In EIGRP, what are the purposes of the hello packets?

A
  1. Discover new neighbors

2. To maintain the neighborship

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18
Q

What is the importance of enable the authentication in a routing protocol?

A

This helps to prevent a Denial of Service (DoS) attack

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19
Q

If in EIGRP you have the following commands:
R1 > “key chain CCNP”

R2 > “key chain Cisco”
Do you think that this could work? And why?

A

Yes, because the name or string only have a locally importance

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20
Q

In EIGRP, how would you configure the authentication?

A
Key chain "string"
     Key 1
            Key-string "string"
Interface fastEthernet 0/1
     Ip authentication mode eigrp 1 md5
     Ip authentication key-chain eigrp  "key-chain-string"
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21
Q

If in EIGRP you have multiple active/valid keys at the same time, which key would be used to generate the MD5 digest to send EIGRP packets?

A

The key with the lowest key number value

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22
Q

In EIGRP how can you check the key chain configuration?

A
  • “show key chain “

* “debug eigrp packet”

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23
Q

Can you configure key chain to use time-based logic?

A

Yes

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24
Q

In EIGRP if you wanted to use different keys during different time periods what would you need to do on router so this configuration could work?

A

The clocks must be set to use the same time, using and NTP or manually through the “clock set” command

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25
Q

Which commands you have to use to configure the key chain to use time-based logic?

A
  • accept-lifetime…

- send-lifetime…

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26
Q

What do you need to do to use different keys during different time periods?

A

The clocks must be set to use the same time. You can configure it manually or using a NTP server (preferred).

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27
Q

Which command you have to use to update the router clock manually?

A

“Clock set” command

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28
Q

In EIGRP, what are the 2 ways that a router has to advertise its connected routes?

A
  1. Using the “network” command

2. Using the “redistribute connected” command

29
Q

What are the advantages and disadvantages of using the “redistribute connected” command?

A

Advantage:
- you don’t have to use the “passive interface” command

Disadvantage:
- you send this routes as external routes

30
Q

How do you configure passive interfaces one by one in EIGRP and all at the same time?

A

Router eigrp
Passive-interface

OR

Passive-interface default

31
Q

Which K values does EIGRP uses by default?

A

Bandwidth (K1) and delay (k3)

32
Q

How many K values are in EIGRP?

A

5

33
Q

What values can have the K-values in EIGRP?

A

1 and 0

34
Q

What is the Administrative Distance (AD) of EIGRP?

A

Internal EIGRP: 90

External EIGRP: 170

35
Q

It is recommended to change the K-values?

A

No

36
Q

You only can configure one key for all the time periods. True or false?

A

False. You can have multiple keys for different time periods

37
Q

For which reasons the EIGRP neighbors can be configured statically?

A
  • L2 media doesn’t support broadcast
  • to ensure that no other device can intercept the EIGRP packets sent to multicast addresses between devices. (A security reason)
38
Q

How can you configure the neighbors statically in EIGRP?

A

Router eigrp

Neighbor

39
Q

What are the caveats or disadvantages of configuring static neighbors in EIGRP?

A
  • all multicast processing for EIGRP on that particular interface is disabled
  • if existing neighbors were formed using multicast, they will go down
  • All the neighbors on that interface must be statically defined
40
Q

With which command can you verify the static neighbors?

A

“Show ip eigrp neighbors detail”

41
Q

For what is used the Router-ID?

A

Is used to prevent external routing loops

42
Q

If 2 routers have the same EIGRP router-id what could happen?

A
  • They won’t be able of becoming neighbors

- Routers won’t accept external updates that have the same router-id

43
Q

What are the characteristics of the EIGRP neighbors over MPLS L3VPN?

A
  • Neighbors are formed with the service provider’s PE router
  • No neighbor relationship is required with all the remote offices/branches/sites or data center
  • It uses Virtual Routing & Forwarding (VRF)
44
Q

What are the characteristics of EIGRP neighbors over Ethernet?

A
  • Is like building a neighbor over a LAN segment

- MetroEthernet configuration is irrelevant to us

45
Q

What are the characteristics of EIGRP neighbors over Frame Relay?

A
  • FR provides layer 2 WAN services
  • Neighbors can be formed with any router that connects to the FR cloud
  • The port can be configured as point-to-point or multipoint (sub or physical interface)
  • It can be dynamic or static neighbor discoveries, depending on the FR cloud
  • There is one significant problem with EIGRP neighbors over FR: split horizon ⛔️
  • A single physical interface from the router connected to the FR cloud, the split horizon became a problem
46
Q

What does a router after forming an EIGRP neighbor relationship?

A

They exchange neighbors topology tables

47
Q

Which information keeps the EIGRP topology table?

A

Prefix
Prefix length
Metric information
Etc

48
Q

What are the 2 ways that a router can use in EIGRP to add routes into its local topology table?

A
  • Prefixes of connected subnets that are matched using the “network” command
  • Prefixes that are redistributed into EIGRP
49
Q

What are the 5 types of protocol messages in EIGRP?

A
  • Hello
  • Update
  • ACK (acknowledgement)
  • Query
  • Reply
50
Q

Which types of messages does EIGRP uses for topology exchange?

A
  • Update

- ACK

51
Q

What information contain the EIGRP update messages?

A
  • Prefix
  • Prefix length
  • Metric components: bandwidth, delay, load and reliability
  • Non metric components: MTU and hop count
52
Q

How is the EIGRP update process?

A
  • When neighbors come up, the routers exchange full topology tables with each table
  • When full topology exchange is done, there is NO period of re-flooding of topology table data
  • If something change only a partial update is sent about the prefix that was affected with a network change
  • If a neighbor fails and then recovers, the full topology table is exchanged with it again
53
Q

An update process in EIGRP can be done for a metric value change?

A

Yes

54
Q

You have to enable split-horizon in EIGRP?

A

No, it is enable by default

55
Q

Which protocol does EIGRP uses to send updates and ACK messages?

A

EIGRP uses RTP ( Reliable Transport Protocol)

56
Q

How is the update process in EIGRP on multi-access network?

A

Typically send update messages to multicast address 224.0.0.10 and expect unicast EIGRP ACK message from each neighbor

57
Q

What is the problem when the split-horizon is enable in EIGRP?

A

The issue happen when we use FR and we have multipoint interfaces. This cause that the update messages can’t be send to all the neighbors

58
Q

How can you disable the split-horizon in EIGRP?

A

“No ip split-horizon eigrp “
Interface subcommand

On RIP
“No ip split-horizon”

59
Q

Which percentage of bandwidth uses EIGRP for the update messages?

A

50% of interface bandwidth by default

60
Q

From where EIGRP take as reference the 50% of bandwidth for updates?

A

From the “bandwidth” command, it uses the 50% of this value

61
Q

How can you change the percentage uses by EIGRP for the update messages?

A

Using the “ip bandwidth-percent eigrp “ command

62
Q

How the bandwidth percentage works in EIGRP when we have PVCs?

A

The bandwidth of the interface is distributed in an equal way for all PVCs, but you can’t define different bandwidth to each PVC

63
Q

What is the feasible distance (FD)?

A

From the local router’s perspective, the metric value for a route, used by this local router, to choose the best route for that prefix

64
Q

What is the Reported Distance (RD) or Advertise Distance (AD)?

A

From the local perspective is the metric reported by the neighbor to reach a route.

70
Q

In this example which is the feasible distance and the reported distance?
10.10.10.0/24 via 18.19.18.18 (668160/640256)

A

Feasible distance: 668168 (metric)

Reported distance: 640256

71
Q

What are the ways to manipulate your the EIGRP metric value?

A
  • Changing bandwidth and/or delay values

- Using offset-list

72
Q

It is recommended to change the bandwidth value to manipulate the metric? Yes or not, and why?

A

It is not recommended because changing the bandwidth may also affect other things as QoS, queuing, shaping, etc

73
Q

What happen when you change the bandwidth and/or delay on an interface?

A

It changes the metric value for all the routes reachable out of that interface

74
Q

Changing the bandwidth or delay affect the FD and RD?

A

No, it only affects the FD