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Exhibit:
In the network segment of the above exhibit, which router is going to become the level-2 DIS
(Designated Intermediate System)?A. CertKing 1B. CertKing 2C. CertKing 3D. CertKing 4E. None
Ans: B
Explanation:
Reserved/circuit type-Top 6 bits reserved; bottom 2 bits value = 0 indicates reserved; value = 1
indicates Level 1; value = 2 indicates Level 2; value = 3 indicates Level 1 and 2.
Reference:
http://www.cisco.com/en/US/tech/ CK3 65/ CK3 81/technologies_white_paper09186a00800a3e6f.shtml
Q6
On a point-to-point IS-IS network connection, what role do PSNP's serve?A. Acknowledge LSPs.B. Replace IIH packets.C. Establish adjacencies.D. Send link-state changes.
Ans: A
Explanation: Partial sequence number PDUs (PSNPs) are used to request an LSP (or LSPs) and
acknowledge receipt of an LSP (or LSPs).
Reference: Cisco, Introduction to Intermediate, System-to-Intermediate System Protocol
http://www.cisco.com/warp/public/cc/pd/iosw/prodlit/insys_wp.htm
Q7
You have a point-to-point network connection with PSNPS' (Partial Sequence Number Packets);
and your junior administrator asks you what purpose they serve. How would you respond?A. acknowledge LSPsB. replace IIH packetsC. establish adjacenciesD. send link-state changes
Ans: A
Explanation: There are four types of IS-IS packets: IS-IS Hello Packets, Link State Packets (LSPs),
Complete Sequence Number Packets (CSNPs), and Partial Sequence Number Packets (PSNPs). PSNPs
function as ACKs. Loss of a PSNP may result in an unnecessary retransmission of an LSP, but does not
prevent correct operation of the routing protocol.
Reference: RFC 1377 - The PPP OSI Network Layer Control Protocol (OSINLCP)'
Q8
Which of the following metrics can be used by IS-IS? (Choose four)A. defaultB. loadC. delayD. expenseE. reliabilityF. error
Ans: A, C, D, F
Explanation:
IS-IS uses a single required default metric with a maximum path value of 1024. The metric is arbitrary
and typically is assigned by a network administrator. Any single link can have a maximum value of 64,
and path links are calculated by summing link values. Maximum metric values were set at these levels
to provide the granularity to support various link types while at the same time ensuring that the shortestpath
algorithm used for route computation will be reasonably efficient. IS-IS also defines three optional
metrics (costs): delay, expense, and error. The delay cost metric reflects the amount of delay on the link.
The expense cost metric reflects the communications cost associated with using the link.
The error cost metric reflects the error rate of the link. IS-IS maintains a mapping of these four metrics
to the quality of service (QoS) option in the CLNP packet header. IS-IS uses these mappings to compute
routes through the Internetwork.
Q9
Which packet type is used to acknowledge LSPs on point-to-point links and to request missing
pieces of information in the IS-IS link state database?A. complete SNP (CSNP)B. partial SNP (PSNP)C. helloD. database queryE. database description packet (DDP)
Ans: B
Explanation:
CSNP-Complete Sequence Number PDUs are used to tell other routers about all the LSPs in one router
database; similar to an OSPF database descriptor packet
PSNP-Partial Sequence Number PDUs are used to request an LSP and acknowledge receipt of an LSP
PDUs (PSNP's) every 3 seconds and complete sequence number PDUs (CSNPs) every 10 seconds that
describe the full database of the DIS. Another router can ask the DIS for a missing LSP using a partial
sequence number packet (PSNP), or in turn give the DIS a new LSP.
Q0
CK1 #show clns interface ethernet 0
Ethernet0 is up, line protocol is up
Checksums enabled, MTU 1497, Encapsulation
SAP
Routing Protocol: ISIS
Circuit Type: level-1-2
Interface number 0x0, local circuit ID 0x1
Level-1 Metric: 10, Priority: 64, Circuit ID: CK2 .02
Number of active level-1 adjacencies: 1
Level-2 Metric: 10, Priority: 64, Circuit ID: CK2 .01
Number of active level-2 adjacencies: 1
Next ISIS LAN Level-1 Hello in 5 seconds
Next ISIS LAN Level-2 Hello in 1 seconds
Refer to the output shown above.
Which statement is correct about IS-IS?A. Router CK1 is the DIS for both L1 and L1B. Router CK1 is the backup DIS for both L1 and L2.C. Router CK2 is the DIS for both L1 and L2.D. Router CK1 is the DIS for L1 and a different router ( CK2 ) is the DIS for L2.E. Router CK1 is the DIS for L2 and a different router ( CK2 ) is the DIS for L1.
Ans: C
It is the DIS that generates the pseudonode Link State Packet (LSP) and is denoted with a non-zero
LSP-ID - R2.01
Q1
You are the network administrator at CertKing . The router topology for the CertKing network is
shown in the following exhibit:
Which router will take on the role of level-2 DIS on this particular segment?F. CertKing 1
G. CertKing 2
H. CertKing 3
I. CertKing 4
Ans: B
Explanation:
Reserved/circuit type-Top 6 bits reserved; bottom 2 bits value = 0 indicates reserved; value = 1
indicates Level 1; value = 2 indicates Level 2; value = 3 indicates Level 1 and 2.
Reference:
http://www.cisco.com/en/US/tech/ CK3 65/ CK3 81/technologies_white_paper09186a00800a3e6f.shtml
Q2
Given the above diagram, which statement correctly matches the letter to the type of IS-IS hello
PDU?A. A=ISH; B=IIH; C:ESHB. A=IIH; B=ESH; C=ISHC. A=ISH; B=ESH; C:IIHD. A=ESH; B=ISH; C=IIHE. A=IIH; B=ISH; C=ESH
Ans: C
Cisco student class manual (BSCI) on page 5-11
Section 13: Describe the hierarchical structure of IS-IS areas (10 Questions)
Q 1
In your network you have two Level-1/ Level-2 IS-IS router named CK1 , and CK2 . The
two routers are connected together by way of a WAN link, and they both belong to the
same area. What kind of a adjacency can you expect them to establish?A. Level-1 onlyB. Level-2 onlyC. both Level-1 and Level-2D. none unless statically configuredE. WAN links do not support IS-IS adjacencies
Ans: A
Explanation: Within an Area Level 1 routing is used. Routing between areas is referred to as
Level 2 routing.
Q2
You have a network segment with an IS-IS level 1-2 router, and you're thinking of
upgrading your network. What is the maximum number of Level-2 routing processes that
this router can belong to?A. 1B. 2C. 30D. 40E. limited only by the router's resources
Ans: A
Explanation: The Cisco IOS software can handle simultaneous operation of up to 30 dynamic IP
routing processes. The combination of routing processes on a router or access server consists of
the following protocols (with the limits noted):
o Up to 30 IGRP routing processes
o Up to 30 OSPF routing processes
o One RIP routing process
o One IS-IS process
o One BGP routing process
o Up to 30 EGP routing processes
Q3
Which IOS command would you enter to if you wanted to see the IS-IS level-2 routing
table?A. show isis routeB. show clns routeC. show isis databaseD. show clns neighbors
Ans: C
Explanation:
The show isis database (detail) command displays the contents of the IS-IS database. Below is
the output of this command when issued on R2. Since IS-IS is a link state protocol, the link state
database should be the same for any router in the same area.
Reference:
http://www.cisco.com/en/US/tech/ CK3 65/ CK3 81/technologies_configuration_example09186a0080
093f38.shtml
Q4
Which of the following types of routers can a Level-2 IS establish adjacencies with? (Select
three)A. Any Level-1 IS in any areaB. Any Level-2 IS in any areaC. Any Level-1 IS in the same areaD. Any Level-1/Level-2 IS in any areaE. Any Level-1/Level-2 IS in the same area
Ans: A, B, D
Explanation:
The key word is 'any area.'
"Each ES lives in a particular area. OSI routing begins when the ESs discover the nearest IS by
listening to ISH packets. When an ES wants to send a packet to another ES, it sends the packet to
one of the ISs on its directly attached network. The router then looks up the destination address
and forwards the packet along the best route. If the destination ES is on the same subnetwork, the
local IS will know this from listening to ESHs and will forward the packet appropriately. The IS
also might provide a redirect (RD) message back to the source to tell it that a more direct route is
available. If the destination address is an ES on another subnetwork in the same area, the IS will
know the correct route and will forward the packet appropriately. If the destination address is an
ES in another area, the Level 1 IS sends the packet to the nearest Level 2 IS. Forwarding through
Level 2 ISs continues until the packet reaches a Level 2 IS in the destination area. Within the
destination area, ISs forward the packet along the best path until the destination ES is reached."
Reference:
Open System Interconnection (OSI) Routing Protocol
http://www.cisco.com/univercd/cc/td/doc/cisintwk/ito_doc/osi_rout.htm
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