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80 Cards in this Set

  • Front
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What makes EIGRP a hybrid routing protocol? Maximum number of hops?
Link State because it forms adjacency to monitor neighbors livelyness - decouples livelness/updates that IGRP and RIP had. now updates can go when needed.

Distance Vector because it is route by rumor.




Can support up to 255 hops but by default supports 100.
Router eigrp 1
Metric Maximum-hops <1-255>

What purpose does split horizon poison serve with EIGRP? How is split horizon configured in classic vs named mode?
To save on route processor of neighboring router. DUAL doesn't need to process the route. It uses DUAL for loop prevention.



classic


Interface x/x


no (ip|ipv6} split-horizon




eigrp named Router


eigrp address-family ipv4 unicast autonmous-system1


Af-interface (interface)


no split-horizon

EIGRP updates are partial or full, periodic or non-periodic, bounded or unbounded?
Partial and Full. Full with new neighbor and partial there after. Periodic. And bounded by quary boundary.
EIGRP - IP Protocol Number, Multicast Address for IP and IPv6 (Source Address for IPv6)?
IP protocol 88, 224.0.0.10, FF02::A and source for IPv6 is link local address
EIGRP Additional Features? Hint Certain Field to tell of another router, multiple protocols, and special markings on packets.
Can advertise next-hop field. Can advertise IPv6 and IPv4. Route Tags used for filtering and route-maps with internal and external routes.
What is composite metric made of?



What role does MTU and Hop Count have on best path selection?

MIn Bandwidth, Summed Delay, Min Reliability, and Max Load



MTU and Hop Count are shared but have no bearing on best path selection. Hop Count will cause route not to be considered if above 100 by default

AD for EIGRP internal and external?
90 for internal and 170 for external
What is RTP? Is there an RTP header?
Reliable Transport Protocol is responsible for reliable transmission for EIGRP. It is trasmitted on IP 88. RTP doesn't have a header but rather is fields inside the EIGRP header.
Give some EIGRP header fields
OPCODE (packet type), Sequence Number, Ack Number, AS, TLV

What are the EIGRP packet types?

Hello, Update, Ack, Query, Reply, SIA Query, and SIA-Reply

What are the EIGRP multicast packet types and functions?
Hello - discover neighbors, liveliness detection



Query - poll neighbors for lost routes




Update - Tell neighbor of new routes

What are the EIGRP unicast packet types and functions?
Hello - when neighbor configured as unicast.



Update - when neighbor is unresponsive, neighbor statement, new neighbor or ptp neighbor; To send routes




Query - when neighbor is unresponsive, neighbor statement or ptp; asking for route, it includes my CD/RD.




Reply - always unicast; is a response to query either with route with RD or no answer




Ack - always unicast; is sent in response to every packet (can also use ACK in another reliable packet) except hello




SIA Query - always unicast; sent to neighbor after query timer expired.




SIA Reply - always unicast; to say I am still working on it

What EIGRP packet types are reliably transmitted or in other words require an ACK?




What kinds of packets can act as ACK as well?

Update, Query, and Reply, SIA Query, and SIA-Reply




All reliably transmitted packets can serve as ACK.

Reliable Transport Protocol Conditional Receive Mode
RTP CR is used when multiple neighbors exist on one segment and some or delayed in acks. Good neighbors can be put into a CR group. Without the CR group I cannot send more packets to neighbor until all have been ACK'd from neighbors.
Hello and Hold Time function and time? Does it need to be the same between neighbors? Configure per interface.
Tells when neighbor is dead. 5 and 15. Nonbroadcast 20 and 60. Doesn't need to be the same between neighbors. Yes, configured per interface



Int fa0/0


ip hello-interval [as-number] [timer]


ip hold-time [as-number] [timer]

For neighbors to establish what must match? Can you use secondary interface?
K Values (1 0 1 0 0 default), common subnets, AS. Authentication if configured. No cannot user secondary interface.
Describe Neighbor Establishment
1. Hello seen from neighbor and placed in pending state. The hello seen on other neighbor and placed in pending state.



2. Null Update sent with SEQ x. Null Update from other neighbor sent with SEQ Y and ACK x. Ack sent with ACK Y




3. Neighbors send full updates with ACKs

What does H, Hold, Uptime, SRTT, RTO, Q Cnt, and Seq mean?
H or Handle represents the number which number connected.



Hold time is time before hello or any EIGRP packet must be heard, uptime is the time neighbor has been up,




SRTT is time it usually takes ACK to come back.




RTO is retransmission timeout for packet that must be resent. It is usually 6xSRTT.




Q Cnt is number of unacked packets.




Seq is the last sequence number from number.

What DUAL analogous to what for RIP? Explain loop avoidance work with DUAL?

DUAL for EIGRP is Bell-Ford for RIP.



It is seeking to find a loop free path by removing all routes as potential backup paths which have reported distanced higher than the historical feasible distance. If a get a update with a reported distance higher than my feasible distance there's no way I can guarantee the route wasn't learned through me.
Explain Feasible Distance
This is the best computed distance of all routes. It is a snapshot and only changes in certain conditions. Current best CD goes lower, best routes RD goes higher than FD, or if it goes active.
Explain Reported Distance and Computed Distance
The RD is the metric advertised by neighbor. The CD is the reported distance of neighbor with the addition of local interface metrics.
What is a succesor, feasible successor, and feasibility condition?
Successor is the route toward neighbor with best RD. It's CD becomes the historical FD. The feasible successor are the routes that meet the Feasibility Condition (dual loop avoidance requirements) but are don't have the best RD. They become backup paths.
Describe active and passive.
Active is when the router use looking for an alternative loop free path. Passive is a stablized state and happens when router found a loop free path.
Describe the topology table. What command will show this information per route?
The topology table store the destination and it's historical Feasible Distance. For each neighbor it's state Passive or Active and next hop along with their Reported Distance/Computed Distance on local router. And the metrics for each vector (load, min bandwidth, total delay, etc.) It will include the external information if available. show ip eigrp topology will show all of this information.
With show ip eigrp topology what does the P mean and two numbers? Does this show all available routes?
The P means route is Passive. A would mean the route is active. Computed Distance, Reported Distance.



No, it shows only the routes that have meet the FC.

With show ip eigrp topology what does the all-links keyword do?
It shows all the links to include the networks that don't meet the FC.
What are the two kinds of computations? And what events lead to computations?
Local and Diffusing.

1. Interface change in cost or state.


2. Update, Query, or Reply packet


3. Neighbor loss which causes router to set CD/RD to infinity for all networks reachable through that neighbor.

Explain local computation.
With local computation the route will modify CD/RD based on the different input events that lead to recalculation initially. Then it check for best CD which meets the FC. If it finds one the route will stay passive and it will send a reply if query came or update. If the new CD is lower it will update the FD.
Explain diffusing computation.
If input event happens and no routes meet FC the route goes active. Diffusing requires the use of neighbors. It will query neighbors to see if they are potential next hops. Neighbor will do a local computation and if it has route it will reply with RD/CD. If it does not it will go active and query neighbors. If neighbor has no route it will reply with infinite metric.
Explain stuck in active (SIA). What the the timer that governs this. What changes if SIA-Query and SIA-Reply are supported?
Stuck in Active means a timers active (3 minutes default) timer expired because router never got reply from router. It will bring down the neighbor if that happens.
If supported what's purpose of SIA-Query and SIA-Reply?
If supported it will increase to six minutes. When SIA condition happens the neighboring router may have been waiting for reply from another neighbor. Bringing down this router penalizes the wrong router. So SIA-Query is sent at half life of timers active timer. The SIA Reply says we are still working on it. This can work it's way down until the problematic router is found it only that neighbor is dropped. This will happen x3 times before dropping the neighbor
What causes a router to go SIA?
Large Diameter, Excessive Redundancy, Overloaded CPU, overloaded links,
What can limit query boundary?
Stub Network and Summarization.
How are loops prevented with external routes.
The EIGRP router-id is used to prevent routing loops with external routes. If a router sees it's own router-id in the advertisement it is not accepted.
EIGRP named configuration allows for what?
To configure IPv4 and IPv6 in one place as address families.

With name configuration what address families are configurable?



Are neighbors, packets, and topology handled separately?

IPv4 unicast and multicast


IPv6 unicast



Yes
With EIGRP name configuration is the name locally significant? What about AS numbers of address families inside of name group? What about AS numbers of address families in different names?
The name is locally signficant. The AS number of address families can be the same. The AS numbers of address families in different names must be unique.
Name moded configuration outline? Basic configuration
Under address family configure af-interface sub config, topology-base sub config, andnetwork and neighbor statements.



router eigrp


address-family ipv4 unicast autonmous-system x


af-interface ....


exit-af-interface


topology-base ....


exit-af-topology


network xxxx


neighbor xxxx

Classic IPv4 Configuration.
router eigrp xxxx

network xxxx


neighbor xxxx


router-id xxxx

What about network 1.1.1.0 255.255.255.0? What does network 1.1.1.0 do?
The parser would reverse the subnet mask to a wildcard and only enable EIGRP on interface beginning with 1.1.1.x.OSPF must have mask. RIP cannot have mask.



network 1.1.1.0 command acts like RIP. This command would change to the classful network of 1.0.0.0 with a wildcard of 0.255.255.255. Any interface which matches would be enabled for EIGRP.

Is split-horizon enabled on all interfaces?
Yes, including Frame Relay unlike RIP. classic



Interface x/x


no (ip|ipv6} split-horizon




eigrpnamed ....


Af-interface


no split-horizon

What are the different neighbor types and how to configure? How is it different from RIP?
Multicast 224.0.0.9 and unicast. If you configure a neighbor statement with interface it will disable hellos on interface and increase TTL to two.



router eigrp 1


neighbor x.x.x.x [interface]




RIP requires passive interface because you cannot specify the interface. OSPF will only accept for non-broadcast interface types.

Configure classic IPv6 EIGRP
ipv6 unicast-routing

!


ipv6 router eigrp 100


no shutdown


router-id [router-id]


!


int f0/0 ipv6 eigrp 100

What must be taken into consideration with the router-id for IPv6?
It must be configured if no IPv4 address is configured locally. The configured router-id doesn't need to be a valid IPv4 address. dotted decimal.
What is the purpose of stub router? How does it signal the stub status? Does neighbor query stub routers?
Purpose is so a spoke configured as stub will not become a transit router. It will not pass any routes learned from other neighbors. The Stub router will set STUB in TLV and upstream understand it will not query stub for networks not advertised by stub. For neighbors that don't understand STUB TLV the stub router will respond with infinite metric when queried.
Can stub routers query each other?
Yes, they can. This is when spokes are connected via shared segment. If one spoke loses hub it is allowed to query other spoke neighbor.
What are the stub types (CSSRR)? Which are defaults? Configure.

CSSRR

connected (default)

summary (default)


static


redistributed.


receive-only




connected still requires interfaces to be config with network statement.




receive-only doesn't send any routes.




Static requires the routes to be redistributed into EIGRP




redistributed will send any routes redistributed into EIGRP.




Router eigrp


eigrp stub < summary | connected | receive-only | static | redistributed | leak-map>

What is a leak-map as it relates to stub configuration? What mechanism is used to match the leak-map?
A leak-map allows for a stub to leak specific networks learned from other neighbors not through connected, static, summary, or redistributed.



Use route-map to say what I want to go out.

What are the two methods of summarization? Besides decreasing route table size what's gain specifically with EIGRP when summarizing.
Auto Summarization and Manual Summarization.



Summarization will limit the query boundary to one deep from summarizing router. R1 has 10.1.0.0/24 and 10.1.2.0/24 and R2 is summarizing to 10.1.0.0/22 to R3. If R1 loses 10.1.0.0/24 it will query R2. R2 will query R3. R3 will respond with a no because it is getting a summary from R2.

Where does auto-summary occur? Is it enabled by default? Why is route matching the summary address for null 0 added?
It only happens on the network boundary. It will not take routes from another neighbor and summarize across the boundary. Only local.



Prior to 15.1 auto-summary was enabled by default. With IPv6 is it not enabled by default.




Routes are added to null 0 to prevent route feedback to prevent looping and using default route. Route Feedback - With RIP auto summary R1 will summary 10.0.0.0/8 to R2 and let's say it's not contiguous and R3 also sends the same summary. R2 will use both and R1 and R3 will also accept each other summary. Traffic destined to 10.1.1.1 will hit R2 (from R4 as an example) hit R1 or R3. If this network doesn't really exist the traffic will loop between R1 and R3 because they have no null route.

Describe manual summarization?
It is configured per interface and can occur at any bit boundary including the default. The more specifics are suppressed. A null route is added with admin distance of 5. The null route can be removed with admin distance of 255.

Int e0/0


ip summary-address eigrp 0.0.0.0 0.0.0.0

What is summary metric and where is it configured?
By default the summary takes the lowest metric from one of the component routes. Drawback is this can cause a lot of change. A static metric can be added is added under router eigrp mode.



router Eigrp ccie


address-family ipv4 unicast autonomous-system 1


topology base


summary-metric 1.1.1.0 255.255.255.0 [bw, delay, etc] distance

Describe EIGRP OTP. What does it replace? What is the encapsulation?
EIGRP Over the Top uses LISP encapsulation. It seeks to replace MPLS L2VPN or DMVPN but provide feel of L2VPN but without the MPLS just IP in middle. LISP separates location and identify or prefix (location) and host (identify) by assigning separate address for location (RLOC) and idenity (EID). LISP control plane using mapping service to connect RLOC and EID. The inner LISP header is between EID and the outer LISP header is between RLOC. With EIGRP it use LISP encapsulation but replaces LISP outer with EIGRP next-hop addresses. The SP must know how to route between EIGRP addresses. The next-hop should be the remote sites SP CE interface. EIGRP uses targeted addresses (neighbor statements) to accomplish this.
Is there a way to protect LISP with encryption?
Yes, with GETVPN.
Configure basic LISP. Why network command for SP interface and why bandwidth statement on LISP interface?
Router eigrp CCIE

address family ipv4 unicast autonomous-system 1


neighbor 1.1.1.1 remote <#-of-hops> lisp-encap


network 1.1.1.2 0.0.0.0


!


Int lisp0


bandwidth 1000000




Current requirement is neighbor command will only work out interfaces enabled for EIGRP. The LISP0 interface defaults to bandwidth 56k. The neighbor command will require static arp or proxy arp enabled on SP.

What feature can be used with LISP to limit number of adjacency requirements? How to configure. Can you limit neighbors?
Route Reflectors. Need to disable split horizon and next-hop self.



router eigrp CCIE


address family ipv4 unicast autonomous-system 1


af-interface g0/0


no next-hop-self


no split-horizon


exit af-interface


remote-neighbors source G0/0 unicast-listener lisp-encap


network 1.1.1.2 0.0.0.0




Optional allow-list acl command to limit neighbors.

What is IP FRR for EIGRP? What is the benefit?
IP Fast Reroute allows for a alternate loop free path to be added to RIB. If the primary fails the alternate can be used immediately. With EIGRP it uses feasible successor.
Cuts down from 100's of ms to 10's of ms.
Configure IP FRR for EIGRP
Router eigrp name

address-family ipv4 unicast automous-system 1


topology base


fast-reroute per-prefix {all | route-map route-map-name}


fast-reroute load-sharing disable


fast-reroute tie-break {interface-disjoint | linecard-disjoint | lowest-backup-path-metric | srlg-disjoint} priority-number

What do these do?

fast-reroute load-sharing disable




fast-reroute tie-break {interface-disjoint | linecard-disjoint | lowest-backup-path-metric | srlg-disjoint} priority-number

By default the router will ECMP on the LFA. If want to enable tie-breakers which will remove LFA routes based on certain criteria then you must disable load-sharing.



Interface-disjoint says remove routes that share same interface as primary


Linecard-disjoint says remove routes that share same linecardlowest-backup..only keeps the lowest metric


srlg removes routes in the same srlg.

How to send a shutdown hello message and what does it contain?
With classic mode IPv4 it is sent when EIGRP interface is shutdown or places into passive mode, removing related network commands, or removing EIGRP process.



With classic IPv6 there is the shutdown command under the process.




With named mode it is also in the af-interface.

What is larger millisecond or microsecond?
Millisecond is msec and mircros is usec. MS is larger.
Which parameters does the composite metric use by default?
Bandwidth and Delay
What value is used to poison route?
Delay
What value is cumulative and which value is determined by the lowest?
Cumulative delay and lowest BW
Which value should be manipulated when traffic engineering?
Delay because changing BW may cause problems with other protocols.
What command to change the weights? Why must they match between neighbors?
router eigrp 1 metric weights tos k1 k2 k3 k4 k5



They must match because neighbors must agree on metric which is used for loop avoidance.

Which k values are on by default
K1 and K3..BW and Delay
What is the formula for metric?
Metric = (10^7/bw in kbps) + (total delay/10) * 256
How is interface metric added?
When the interface is added to EIGRP a composite metric is computed and reported to all neighbotrs. Each neighbor adds the cost of the inbound interface.
What command is used to set the default metric for all EIGRP redistributed routes?
router eigrp 100

default-metric [bandwidth delay reliability loading mtu]

What are wide metrics which EIGRP? Why is it neccesary?
10 Gig in the standard was 1 and 10 ms was 1. Anything higher (BW) or lower (delay) was 1. It changes metric from 32bit to 64bit. Multiplies the equation by 65536 (that's the extra 32 bits)
Will the RIB show the wide metric? What's command?
No the RIB only supports 32 bit. The calculation is based on the wide but the RIB will show the scaled down.



metric rib-scale 128

What mode supports EIGRP wide metrics?


Is delay still displayed in ms?

EIGRP named moded


Delay displayed in picoseconds.

What does EIGRP do with equal cost paths?
Max-paths of 4 by default. Up to 4 equal cost paths will be added.
What does variance do? What is the default variance?
It provides the abilitiy to add unequal cost pahts to the RIB. It multiplies the FD by a value. Once multiplied you know have a new FD. Any route that already meet the FC will know go into the RIB if the CD is equal to or less than the new FD.



The default is 1.

What variance is needed to get all four of these routes added? And does variance directly influence traffic share?Metric: 125,000 225,000 255,000 300,00
Highest/lowest 300,000/125,000 = 2.4. 3 x 125,000 is 375,000.Variance doesn't directly influence traffic share. But variance determines how many routes are added and traffic is then divided proportionally.


300,000 / 125,000 = 2.4


300,000 / 225,000 = 1.3333


300,000 / 255,000 = 1.1765


300,000 / 300,000 = 1

What is add paths feature?
It provides EIGRP with the ability to send other best paths.
In what topologies is Add Paths useful for?
DMVPN when your spokes have redundancy. Must remember that DMVPN hubs don't advertise their next-hop because of no next-hop-self command. Spokes will get true next hop. If a site has two spoke routers then other sites could pontentially get both routes. Problem is hub will only send the best path. Add paths allows hub to send more than one.
Do variance and add paths work together?
No, variance must be left at default of 1.
What configurations are needed at the hub?
router eigrp CCIE

Address-family ipv4 unicast autonomous-system 1


topology base


variance 1


maximum-paths 6


!


af-interface tunnel0


no split-horizon


no next-hop-self


add paths 4