A link state routing protocol advertises, to it’s neighbors, the state of the link when the state of the link changes.
A distance vector routing protocol advertises its routing table periodically.
9. [CxNx] Of the following commands, identify the correct one for clearing the IP arp table in memory of the router.
a) clear ip arp-cache
b) clear ip arp-table
c) clear arp-cache
d) clear arp-table
e) clear arp-ram
Answer
c) clear arp-cache
If you have changed an ip address or a NIC card on a host you might use this command to reset the cache.
10. [CxNx] Which of the following explains the correct definition of administrative distance as it pertains to Cisco’s IOS?
a) The process by which routers select an administrator for an autonomous system.
b) The process where a router will select the best path to a destination network.
c) The process where a router will distance itself from other routers due to it’s lack of administrative experience.
d) The process where a router will prioritize routing protocols so that in the event two routing protocols have conflicting next hop addresses, the routing protocol with the lowest administrative distance will take priority.
e) The process where a router will prioritize routing protocols so that in the event two routing protocols have conflicting next hop addresses, the routing protocol with the highest administrative distance will take priority.
Answer
d) The process where a router will prioritize routing protocols so that in the event two routing protocols have conflicting next hop addresses, the routing protocol with the lowest administrative distance will take priority.
Cisco uses administrative distances (AD) to measure the reliability of the routing protocol. The lower the (AD) the more reliable the protocol.
Router_C#sh ip route
Codes: C - connected, S - static,
I - IGRP, R - RIP,
M - mobile, B - BGP
D - EIGRP, EX - EIGRP external, O - OSPF,
IA - OSPF inter area
N1 - OSPF NSSA external type 1, N2 - OSPF
NSSA external type 2
E1 - OSPF external type 1,
E2 - OSPF external type 2,
E - EGP
i - IS-IS, L1 - IS-IS level-1,
L2 - IS-IS level-2, * -
candidate default
U - per-user static route, o - ODR
Gateway of last resort is not set
172.16.0.0/24 is subnetted, 2 subnets
C 172.16.1.0 is directly connected,
Serial1
C 172.16.2.0 is directly connected,
Serial0
I 10.0.0.0/8 [100/8576] via 172.16.1.1,
00:00:09, Serial1
[100/8576] via 172.16.2.1, 00:00:19,
Serial0
The 100 in bold is the administrative
distance for IGRP.
A partial list of administrative distances is included below:
Protocol AD
EIGRP 90
IGRP 100
OSPF 110
RIP 120
BGP 180
If a router hears a IP RIP and a IGRP update for the same network the router will discard the rip information. IP RIP uses hop count as it’s metric, while IGRP uses a composite metric including bandwidth and load, speed is the primary consideration.
11. [ExNx] Collisions occur when
a) multiple packets are placed on a serial link
b) multiple stations listen for traffic and transmit at the same time
c) when multiple tokens are on a ring simultaneously
d) beaconing process takes place
Answer
b) multiple stations listen for traffic and transmit at the same time
Collisions is a term that is used in an ethernet environment. Ethernet can be described as a listen then transmit scenario. First a station will listen for traffic if no traffic is sensed then a transmission will take place. If two stations transmit at the same time collisions will occur. The first station to detect the collision sends out a jamming signal to alert all stations a collision has occurred. At this point these stations set up a random interval timer when the timer expires re-transmission will occur.
Token ring is a token passing process a station can transmit only when he has the token. There never can be multiple tokens on the ring. Early token release allows up to two data frames to be transmitted on a token ring LAN at the same time. Collisions do not occur on a token ring.
Because of the point to point nature of serial links collisions do not occur.
Beaconing is a term used in a token passing environment.
12. [RINx] How many subnets are possible with a Class C address and a subnet mask of 255.255.255.252?
a) 32
b) 30
c) 60
d) 62
e) 4
Answer
d) 62
The above mask is using 6 bits to describe subnets. The formula used to determine the number of subnets (not including the all 0’s or all 1’s subnet) is 2n - 2 were n is the number of subnet bits. This is the number to use when configuring a ip address with the setup dialog.
13. [RxNx] What commands will list all protocols that are currently being routed? (Choose all that apply.)
a) show ip protocol
b) show protocol
c) show run
d) show start
e) All of the above
Answer
b) show protocol
c) show run
Show ip protocol will show just the ip routing protocols that are currently configured. Show start may or may not show the current routed protocols.
Below is the output of show protocol
Router_B#show protocol
Global values:
Internet Protocol routing is enabled
Appletalk routing is enabled
BRI0 is administratively down, line protocol is down
BRI0:1 is administratively down, line protocol is down
BRI0:2 is administratively down, line protocol is down
Serial0 is administratively down, line protocol is down
Serial1 is administratively down, line protocol is down
Serial2 is administratively down, line protocol is down
Serial3 is administratively down, line protocol is down
TokenRing0 is administratively down, line protocol is down
14. [xxNx] Which of the following are true of access lists?
a) Access list should have at least one permit statement.
b) The last configured line should always be a permit statement.
c) Every access-list will implicitly deny all traffic.
d) Access-lists are processed top down.
e) All of the above.
Answer
e) All of the above.
Every access list has an implicit deny all at the end. What would the need be to create a access list with just deny statements. Access-list are processed from the top down therefore the order of each statement could be critical, for instance suppose you created an access list and the first line was a permit any and the next line was a deny. Since it’s top down processing a packet would be permitted to pass on the first line and the second line would never be executed. An extended list will give you a "match count" that will help in determining what the most efficient order should be.
15. [xxNx] If the access-group command is configured on an interface and there is no access-list created which of the following is most correct?
a) An error message will appear.
b) The command will be executed and deny all traffic out.
c) The command will be executed and permit all traffic out.
d) The command will be executed and permit all traffic in and out.
e) The command will be executed and deny all traffic in and out.
Answer
d) The command will be executed and permit all traffic in and out.
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