EIGRP COPY Flashcards
Are keys case sensitive?
Yes
If there are multiple valid, matching keys, which key will be used?
The one with the lowest number (first match)
Give the command to display a key chain
show key chain
What are the two ways to add interfaces to EIGRP and what are the administrative distances for these?
network command - Internal route - AD 90
redistribute connected command - External route - AD 170
What two things does “passive-interface” do?
It stops the interface from sending Hello packets and will also ignore incoming ones.
Give the command to set all interfaces as passive except Ethernet0/0
router eigrp
passive-interface default
no passive-interface Ethernet0/0
What command will show EIGRP interfaces in passive mode?
sh ip protocols
Which K-values are used in the default metric?
bandwidth (k1) and delay (k3)
How is the router-id chosen?
The highest numbered active loopback is used, or the highest numbered active interface if no loopback is available.
Can two routers with the same router-id become neighbors? Can they exchange routes?
They can become neighbors but cannot exchange routes if directly connected to each other. They will accept internal routes if there is another router between the two.
Give the command to manually set a router-id
router eigrp 100
eigrp router-id X.X.X.X
What extra information does an external route update include?
It includes the originating router’s router-id as well as the external metric and protocol.
Give the command to disable split-horizon for EIGRP on an interface.
interface serial0/0
no ip split-horizon eigrp
What does the following command do?
interface serial0/0
no ip split-horizon
It will disable split-horizon for RIP only.
How much bandwidth total will EIGRP use on a given link?
By default, EIGRP uses only 50% of the available bandwidth.
Give the command to change the percentage of bandwidth EIGRP will use on interface serial0/0.
interface serial0/0
ip bandwidth-percent eigrp
Explain the difference between access-rate and CIR.
Access rate is the fastest rate a connection can physically handle. Committed information rate (CIR) is the guaranteed available rate.
Does the bandwidth command set the access rate or the CIR? Without it, what is used?
It sets the CIR. Without the bandwidth command, the CIR defaults to the access rate.
What unit does the bandwidth command use?
kilobits per second
What is the assumed bandwidth rate on a serial interface unless otherwise specified?
1544 kbps
What should the bandwidth command be set to for point-to-point and multipoint links?
On point-to-point, use bandwidth to set the CIR. On multipoint, set bandwidth to the sum of all the CIRs.
How does EIGRP determine the available bandwidth in multipoint links?
Bandwidth should be set to the sum of the CIRs. EIGRP will divide this by the number of PVCs, and use 50% of that value for each connection.
What impact does “set ip bandwidth-percent” have on a multipoint link?
EIGRP will divide the number given by the number of PVCs.
How is the reported distance sent?
The sending router sends the raw values and the receiving router calculates the reported distance (RD).
How does as a receiving router calculate the feasible distance?
It adds the delay for the distance to the sending router, and also replaces the bandwidth value if the bandwidth between it and the sending router is slower than the current minimum bandwidth, then recalculates.
What are the values given as (x, y) in “show ip eigrp toplogy”?
(feasible distance, reported distance)
What unit is used in the “delay” command on an interface? What unit is displayed with “show interface”?
The delay command uses tens of microseconds but the show command will display it in microseconds.
What are the two ways of manipulating EIGRP metrics?
1) Change delay and/or bandwidth
2) Use an offset-list
Of delay and bandwidth, which is preferred to modify?
Delay is preferred, because other protocols also use the bandwidth command.
Does changing the delay or bandwidth impact a sending neighbor’s reported distance?
No
What are the two ways of matching all ip addresses with an off-set list?
Use any/any in the access-list, or reference access-list 0.
Does adding/removing an offset-list cause adjacencies to drop?
Yes
What does “sh ip eigrp topology” show by default? Give the command to see everything in the topology table.
It shows only successors and feasible successors.
sh ip eigrp topology all-links
What does an inbound versus an outbound offset-list do?
An inbound list changes the router’s local value plus the value it will report.
An outbound list changes only the reported value.
On the packet level, how is an offset-list implemented?
As delay
Can an offset-list decrease the value of the EIGRP metric?
No
What are the the conditions for choosing a feasible successor?
The feasible successor must have the same AD metric as the successor, and must satisfy the feasible condition. The feasibility condition states the feasible successor’s reported distance must be less than the successor’s feasible distance.
What does a Query include?
The query includes poisoned route information, including a maximum bandwidth and infinite delay.
What does a negative reply to a query include?
The reply includes a router-id with all zeros and a different value for the type of network. The delay is also maxxed out.
What is the active timer?
The active timer is the amount of time before a neighbor that doesn’t respond to a query is considered Stuck in Active and the adjacency is torn down.
What is the default active timer value?
The default active timer value is 3 minutes.
How much time must elapse before a SIA Query is sent to a non-responsive neighbor?
Half of the active timer value, so roughly 90 seconds by default.
What happens if a router receives an answer to a SIA Query?
If the neighbor sends back a SIA Reply, the active timer will be reset.
If a route is lost, what happens to it while the router goes through the Active route process?
The stale route remains in the routing table.
What are two ways to limit the scope of EIGRP active route queries?
Stub routers and router summarization
What is a stub router?
A stub router will not advertise learned routes amongst its neighbors by default. Other routers will also not send Query packets to it.
Give the command to change the default active timer to one minute.
router eigrp 100
timers active-time 1
By default, what will a stub router advertise?
It will advertise only connected and summary routes by default.
Give the command to set a router as a stub router that will advertise its redistributed routes as well as the default options.
router eigrp 100
eigrp stub connected summary redistributed
What options does an offset-list take for input?
Standard access-list only
What is the netmask for matching all bits?
255.255.255.255
What is the syntax to match all routes on a prefix-list?
0.0.0.0/0 le 32
What does variance enable?
Variance allows the installation of unequal cost routing paths into the routing table. By default, it is set to 1, meaning it only allows equal paths.
How is an extended ACL interpreted when used as a distribution list?
The source is evaluated as the sending neighbor IP address, and the destination is evaluated as the prefix in the update.
What is a distribute-list used for?
It can limit which routes are accepted and/or sent to neighbors.