Cisco 642-885 Certification Exam,The Most Recommended Cisco 642-885 PDF Is Your Best Choice

CCNP Service Provider, Cisco Comments Off

Attention Please:Professional new version Cisco 642-885 PDF and VCE dumps can now free download on Flydumps.com,all are updated timely by our experts covering all Cisco 642-885 new questions and questions.100 percent pass your Cisco 642-885 exam.

Exam A
QUESTION 1
You noticed a recent change to the BGP configuration on a PE router, the bgp scan time has been changed from the default value to 30s. Which three effects will this change have? (Choose three.)
A. The BGP table will be examined and verified more frequently
B. The BGP keepalive messages will be sent to the BGP peers at a faster rate
C. The BGP table will be modified more quickly in the event that a next-hop address becomes unreachable
D. The CPU load of the router will increase
E. The minimum time interval between sending EBGP and IBGP routing updates will decrease
F. The BGP convergence time will increase

Correct Answer: ACD Section: (none) Explanation
Explanation/Reference:
QUESTION 2
On Cisco IOS-XR, which BGP process can be distributed into multiple instances?
A. BGP process manager
B. BGP RIB process
C. BGP speaker process
D. BGP scanner process
E. BGP dampening process

Correct Answer: C Section: (none) Explanation
Explanation/Reference:
Cisco IOS XR allows you to control the configuration of the number of distributed speakers
and enables you to selectively assign neighbors to specific speakers. On the CRS-1 platform,
multiple speaker processes up to 15 may be configured. However, configuring all the
different speakers on the primary route processor simply adds to the load on the single RP.
Distributed speaker functionality is useful if Distributed Route Processor (DRP) hardware
is available to take advantage of process placement. Later sections in this chapter depict distributed
BGP and placement of BGP process speakers on DRPs on a CRS-1 router.
In addition to the speaker process, BPM starts the bRIB process once BGP is configured.

bRIB process is responsible for performing the best-path calculation based on partial best paths received from the speaker processes. The best route is installed into the bRIB and is advertised back to all speakers. The bRIB process is also responsible for installing routes

QUESTION 3
Refer to the configuration exhibit, taken from a Cisco IOS-XR router. Which configuration change is required to properly enable this router as the signaling router for implementing source-based RTBH filtering?

A. set community (no-export) in the route policy
B. pass in the route policy “First Test, First Pass” – www.lead2pass.com 4 Cisco 642-885 Exam
C. set local-preference 1000 in the route policy
D. The 192.0.2.1/32 static route should be tagged as 666 (tag 666)

Correct Answer: A Section: (none) Explanation
QUESTION 4
Refer to the Cisco IOS-XR BGP configuration exhibit. Identify two configuration errors. (Choose two.)

A. The neighbor-group efg is missing the ebgp-multihop 2 configuration
B. The ttl-security configuration command is missing the option to set the number of hops
C. The passall route policy is wrong
D. The route-policy passall in and route-policy passall out commands should be configured under the neighbor-group efg instead of the af-group abc
E. The maximum-prefix 10 configuration should be configured under the af-group abc instead of the neighbor-group efg

Correct Answer: CE Section: (none) Explanation
Explanation/Reference:
http://www.cisco.com/en/US/tech/tk365/technologies_configuration_example09186a008010a28a.shtml

QUESTION 5
Which two statements correctly describe the RPF check when a multicast packet arrives at a router? (Choose two.)
A. The router looks up the source address in the unicast routing table to determine if the packet has arrived on the interface that is on the reverse path back to the source
B. The router looks up the destination address in the unicast routing table to determine if the packet has arrived on the interface that is on the reverse path back to the destination “First Test, First Pass” -www.lead2pass.com 5 Cisco 642-885 Exam
C. If the packet has arrived on the interface leading back to the destination, the RPF check passes and the packet is forwarded. If the RPF check fails, the packet is dropped
D. If the packet has arrived on the interface leading back to the source, the RPF check passes and the packet is forwarded. If the RPF check fails, the packet is dropped

Correct Answer: AD Section: (none) Explanation
Explanation/Reference:

Reverse Path Forwarding (RPF)
RPF is a fundamental concept in multicast routing that enables routers to correctly forward multicast traffic down the distribution tree. RPF makes use of the existing unicast routing table to determine the upstream and downstream neighbors. A router will only forward a multicast packet if it is received on the upstream interface. This RPF check helps to guarantee that the distribution tree will be loop free.

RPF Check
When a multicast packet arrives at a router, the router will perform an RPF check on the packet. If the RPF
check is successful, the packet will be forwarded. Otherwise it will be dropped.
For traffic flowing down a source tree, the RPF check procedure works as follows:

Step 1. Router looks up the source address in the unicast routing table to determine if it has arrived on
the interface that is on the reverse path back to the source.

Step 2. If packet has arrived on the interface leading back to the source, the RPF check is successful
and the packet will be forwarded.

Step 3. If the RPF check in 2 fails, the packet is dropped.
QUESTION 6
Refer to the Cisco IOS-XR show output exhibit. Which statement is correct?

A. The [ ] indicates the configuration has a problem
B. The [ ] indicates the 10.1.1.1 neighbor peering session has not been established
C. The [ ] indicates the configuration was not inherited from a group
D. The [ ] indicates the configuration has not been committed
E. The [ ] indicates the corresponding BGP peer configuration has a mismatch configuration

Correct Answer: C Section: (none) Explanation
Explanation/Reference: show bgp neighbors
Use the show bgp neighbors command to display information about the BGP configuration for neighbors.
.
Use the configuration option to display the effective configuration for the neighbor, including any settings that have been inherited from session groups, neighbor groups, or af-groups used by this neighbor.

.
Use the inheritance option to display the session groups, neighbor groups, and af-groups from which this neighbor inherits configuration settings.
The following example displays sample output from the show bgp af-group command using the configuration keyword. This example shows where each configuration item was inherited from. The default-originate command was configured directly on this address family group (indicated by [ ]). The remove-private-as command was inherited from address family group GROUP_2, which in turn inherited from address family group GROUP_3:
RP/0/0/CPU0:router# show bgp af-group GROUP_1 configuration af-group GROUP_1 address-family ipv4 unicast
capability orf prefix-list both [a:GROUP_2]
default-originate []
maximum-prefix 2500 75 warning-only []
policy POLICY_1 in [a:GROUP_2 a:GROUP_3]
remove-private-AS [a:GROUP_2 a:GROUP_3]
send-community-ebgp [a:GROUP_2]
send-extended-community-ebgp [a:GROUP_2
QUESTION 7

When enabling interdomain multicast routing, which two statements are correct? (Choose two.)
A. Multiprotocol BGP is used instead of PIM SM to build the intradomain and interdomain multicast distribution trees
B. Use MSDP to enable the RPs from different domains to exchange information about active multicast sources
C. MSDP SA packets are sent between the multiprotocol BGP peers
D. Noncongruent unicast and multicast topologies can be supported using multiprotocol BGP

Correct Answer: BD Section: (none) Explanation
Explanation/Reference:
http://prakashkalsaria.wordpress.com/2010/08/11/mbgp-msdp/

MSDP
In the PIM-SM model, multicast sources and receivers must register with their local RP. Actually, the router closest to the sources or receivers registers with the RP, but the key point to note is that the RP knows about all the sources and receivers for any particular group. RPs in other domains have no way of knowing about sources located in other domains. MSDP is an elegant way to solve this problem. MSDP is a mechanism that allows RPs to share information about active sources. RPs know about the receivers in their local domain. When RPs in remote domains hear about the active sources, they can pass on that information to their local receivers and multicast data can then be forwarded between the domains. A useful feature of MSDP is that it allows each domain to maintain an independent RP that does not rely on other domains, but it does enable RPs to forward traffic between domains. PIM-SM is used to forward the traffic between the multicast domains. The RP in each domain establishes an MSDP peering session using a TCP connection with the RPs in other domains or with border routers leading to the other domains. When the RP learns about a new multicast source within its own domain (through the normal PIM register mechanism), the RP encapsulates the first data packet in a Source-Active (SA) message and sends the SA to all MSDP peers. The SA is forwarded by each receiving peer using a modified RPF check, until the SA reaches every MSDP router in the interconnected networks〞theoretically the entire multicast internet. If the receiving MSDP peer is an RP, and the RP has a (*, G) entry for the group in the SA (there is an interested receiver), the RP creates (S, G) state for the source and joins to the shortest path tree for the source. The encapsulated data is decapsulated and forwarded down the shared tree of that RP. When the packet is received by the last hop router of the receiver, the last hop router also may join the shortest path tree to the source. The MSDP speaker periodically sends SAs that include all sources within the own domain of the RP
http://www.cisco.com/en/US/docs/ios_xr_sw/iosxr_r3.2/routing/configuration/guide/rc32bgp.html
Multiprotocol BGP
Multiprotocol BGP is an enhanced BGP that carries routing information for multiple network layer protocols and IP multicast routes. BGP carries two sets of routes, one set for unicast routing and one set for multicast routing. The routes associated with multicast routing are used by the Protocol Independent Multicast (PIM) feature to build data distribution trees.
Multiprotocol BGP is useful when you want a link dedicated to multicast traffic, perhaps to limit which resources are used for which traffic. Multiprotocol BGP allows you to have a unicast routing topology different from a multicast routing topology providing more control over your network and resources.
In BGP, the only way to perform interdomain multicast routing was to use the BGP infrastructure that was in place for unicast routing. Perhaps you want all multicast traffic exchanged at one network access point (NAP). If those routers were not multicast capable, or there were differing policies for which you wanted multicast traffic to flow, multicast routing could not be supported without multiprotocol BGP.
Note It is possible to configure BGP peers that exchange both unicast and multicast network layer reachability information (NLRI), but you cannot connect multiprotocol BGP clouds with a BGP cloud. That is, you cannot redistribute multiprotocol BGP routes into BGP.
QUESTION 8
The 224.192.16.1 multicast IP address maps to which multicast MAC address?
A. 01-00-5E-C0-10-01
B. 01-00-5E-40-10-01
C. 01-00-5E-00-10-01
D. 01-00-5E-C0-16-01

Correct Answer: B Section: (none) Explanation
Explanation/Reference:
least significant 23 bits of IP address and pre-pend 01-00-5E
224 ignore 192 less 128 becomes 64 = 40 16 = 10 1 = 01 01-00-5E-40-10-01
QUESTION 9
“First Test, First Pass” – www.lead2pass.com 6 Cisco 642-885 Exam
The following Cisco IOS-XR configuration command will globally enable which multicast process(es) on the router?
RP/0/RP0/CPU0:router(config)# multicast-routing
A. IGMP only
B. PIM only
C. IGMP and MLD only
D. PIM and IGMP only
E. PIM and IGMP and MLD

Correct Answer: E Section: (none) Explanation
Explanation/Reference:
http://www.cisco.com/en/US/docs/ios_xr_sw/iosxr_r3.5/multicast/configuration/guide/mc35mcst.html
Multicast-routing Configuration Submode
When you issue the multicast-routing ipv4 or multicast-routing ipv6 command, all default multicast components (PIM, IGMP, MLD, MFWD, and MRIB) are automatically started, and the CLI prompt changes to “config-mcast-ipv4” or “config-mcast-ipv6”, indicating that you have entered multicast-routing configuration submode
QUESTION 10
When implementing interdomain multicast routing, which mechanism can be used to advertise multicast sources in one domain to the other domains, allowing the RPs to build interdomain multicast distribution trees?
A. Multiprotocol BGP
B. PIM
C. MSDP
D. Auto RP
E. BSR
F. MLD
Correct Answer: C Section: (none) Explanation
Explanation/Reference:
Multicast Source Discovery Protocol

Multicast Source Discovery Protocol (MSDP) is a mechanism to connect multiple PIM sparse-mode domains. MSDP allows multicast sources for a group to be known to all rendezvous point(s) (RPs) in different domains. Each PIM-SM domain uses its own RPs and need not depend on RPs in other domains.
An RP in a PIM-SM domain has MSDP peering relationships with MSDP-enabled routers in other domains. Each peering relationship occurs over a TCP connection, which is maintained by the underlying routing system.
MSDP speakers exchange messages called Source Active (SA) messages. When an RP learns about a local active source, typically through a PIM register message, the MSDP process encapsulates the register in an SA message and forwards the information to its peers. The message contains the source and group information for the multicast flow, as well as any encapsulated data. If a neighboring RP has local joiners for the multicast group, the RP installs the S, G route, forwards the encapsulated data contained in the SA message, and sends PIM joins back towards the source. This process describes how a multicast path can be built between domains.
QUESTION 11
Which two statements regarding Auto RP operations and implementations are correct? (Choose two.)
A. Candidate RPs send RP announcements to the 224.0.1.39 multicast group, and the mapping agents send RP discovery messages to the 224.0.1.40 multicast group
B. Every PIM-SM router must be configured with the RP mapping agent IP address
C. Candidate RPs learn the IP address of the mapping agents via periodic RP discovery messages
D. Administrative scoping can be configured to limit the scope of the RP announcements
E. A Reverse Path Forwarding check is done on the RP discovery messages
F. RP discovery messages are flooded hop by hop throughout the network as multicast to the all PIM routers multicast group with a TTL of 1
Correct Answer: AD Section: (none) Explanation
Explanation/Reference: Auto-RP
Automatic route processing (Auto-RP) is a feature that automates the distribution of group-to-RP mappings
in a PIM network. This feature has these benefits:
It is easy to use multiple RPs within a network to serve different group ranges.
It allows load splitting among different RPs.
It facilitates the arrangement of RPs according to the location of group participants.
It avoids inconsistent, manual RP configurations that might cause connectivity problems.
Multiple RPs can be used to serve different group ranges or to serve as hot backups for each other. To
ensure that Auto-RP functions, configure routers as candidate RPs so that they can announce their
interest in operating as an RP for certain group ranges. Additionally, a router must be designated as an
RP-mapping agent that receives the RP-announcement messages from the candidate RPs, and arbitrates
conflicts. The RP-mapping agent sends the consistent group-to-RP mappings to all remaining routers.
Thus, all routers automatically determine which RP to use for the groups they support

auto-rp candidate-rp
To configure a router as a Protocol Independent Multicast (PIM) rendezvous point (RP) candidate that
sends messages to the well-known CISCO-RP-ANNOUNCE multicast group (224.0.1.39), use the auto-rp

candidate-rp command in PIM configuration mode. To return to the default behavior, use the no form of
this command.

auto-rp candidate-rp type interface-path-id scope ttl-value [ group-list access-list-name ] [ interval seconds ] [bidir]
no auto-rp candidate-rp type interface-path-id scope ttl-value [ group-list access-
list-name ] [ interval seconds ] [bidir]

QUESTION 12
What is determined by running the same hash algorithm on all PIMv2 routers?
A. The SPT from the RP to the multicast source
B. The SPT from the last hop router to the multicast source
C. Auto RP election
D. Which BSR to use for a particular multicast group “First Test, First Pass” – www.lead2pass.com 7 Cisco 642-885 Exam E. Which RP to use from a set of candidate RPs in the RP set
Correct Answer: E Section: (none) Explanation
Explanation/Reference:

QUESTION 13
When configuring PIM operations, what is the effect of setting the SPT threshold to infinity?
A. The multicast source to the RP path will never switch over to the shortest path tree
B. All the PIM routers will have more (S,G) states, thus consuming more router resources
C. The receivers will be able to immediately switch over to the shortest path tree after receiving the first multicast packets on the shared tree via the RP
D. The last-hop routers will never switch over to the shortest path tree and will always remain on the shared tree

Correct Answer: D Section: (none) Explanation
QUESTION 14
Which multicast group range is reserved for SSM?
A. 224.0.0.0/8
B. 225.0.0.0/8
C. 232.0.0.0/8
D. 239.0.0.0/8

Correct Answer: C Section: (none) Explanation
Explanation/Reference: PIM-SSM Operations
PIM in Source Specific Multicast operation uses information found on source addresses for a multicast group provided by receivers and performs source filtering on traffic.
.
By default, PIM-SSM operates in the 232.0.0.0/8 multicast group range for IPv4 and ff3x::/32 (where x is any valid scope) in IPv6. To configure these values, use the ssm range command.

.
If SSM is deployed in a network already configured for PIM-SM, only the last-hop routers must be upgraded with Cisco IOS XR software that supports the SSM feature.

.
No MSDP SA messages within the SSM range are accepted, generated, or forwarded
QUESTION 15
Which four statements are correct regarding MSDP configurations and operations? (Choose four.)
A. The MSDP peers are also typically the RPs in respective routing domains.
B. SA messages are flooded to all other MSDP peers without any restrictions
C. On Cisco IOS, IOS-XE, and IOS-XR, the router can be configured to cache the SA messages to reduce the join latency
D. SA messages are used to advertise active sources in a domain
E. MSDP establishes neighbor relationships with other MSDP peers using TCP port 639
F. MSDP peerings on Cisco IOS, IOS-XE, and IOS-XR support MD5 or SHA1 authentication

Correct Answer: ACDE Section: (none) Explanation
Explanation/Reference:
http://www.cisco.com/en/US/docs/ios/ipmulti/configuration/guide/imc_msdp_im_pim_sm.html
When MSDP is enabled, an RP in a PIM-SM domain maintains MSDP peering relationships with MSDP-enabled routers in other domains. This peering relationship occurs over a TCP connection, where primarily a list of sources sending to multicast groups is exchanged. MSDP uses TCP (port 639) for its peering connections. As with BGP, using point-to-point TCP peering means that each peer must be explicitly configured. The TCP connections between RPs, moreover, are achieved by the underlying routing system. The receiving RP uses the source lists to establish a source path. If the multicast sources are of interest to a domain that has receivers, multicast data is delivered over the normal, source-tree building mechanism provided by PIM-SM. MSDP is also used to announce sources sending to a group. These announcements must originate at the RP of the domain.
QUESTION 16
When verifying multicast configurations and operations on Cisco IOS-XR routers, which two statements regarding show commands are correct? (Choose two.)
A. Use the show route ipv4 multicast command to display the incoming and outgoing interface lists for each of the joined multicast groups
B. Use the show pim rpf command to display the RPF information for the RP or for the multicast source
C. Use the show mrib route command to display the (*,G) and (S,G) states information on the router
D. Use the show mrib route command to display the configured static multicast routes “First Test, First Pass” – www.lead2pass.com 8 Cisco 642-885 Exam

Correct Answer: BC Section: (none) Explanation
Explanation/Reference: QUESTION 17

Assume that the R1 router is enabled for PIM-SM and receives a multicast packet sourced from 172.16.1.100, and the R1 router has multicast receivers on the Gi0/1, Gi0/2, Gi0/3 and Gi0/4 interfaces. The multicast packet from the 172.16.1.100 source must arrive on which interface on the R1 router for it to be forwarded out the other interfaces?

A. Gi0/1
B. Gi0/2
C. Gi0/3
D. Gi0/4
E. Gi0/1 or Gi0/2 or Gi0/3 or Gi0/4
F. Gi0/2 or Gi0/3
G. Gi0/1 or Gi0/4

Correct Answer: A Section: (none) Explanation
QUESTION 18
Refer to the exhibit. Which statement correctly explains the bgp graceful-restart command?

A. This command is used to enable NSR and is entered on the NSR-capable router, and also on any NSR-aware peer
B. This command is used to enable NSF and is entered on the NSF-capable router, and also on any NSF-aware peer
C. This command is only required on the NSF-capable routers to enable BGP graceful restart with the BGP peers
D. This command is only required on the NSF-aware routers to enable BGP graceful restart with the BGP peers
E. This command is only required on the NSR-capable routers to enable BGP graceful restart with the BGP peers

Correct Answer: B Section: (none) Explanation
Explanation/Reference:
Graceful restart is supported in recent versions of Cisco IOS software (12.0S) and is supported in Cisco IOS XR software. Graceful restart is the mechanism by which BGP routing peers avoid changes to their forwarding paths following a switchover. If the BGP peer has received this capability, it is aware that the device sending the message is nonstop forwarding (NSF)-capable. Both the NSF-capable router and its BGP peers (NSF-aware peers) need to exchange the graceful restart capability in their OPEN messages, at the time of session establishment. If both peers do not exchange the graceful restart capability, the session will not be graceful restart-capable.
If the BGP session is lost during a Route Processor (RP) switchover or BGP process restart, the NSF-aware BGP peer marks all the routes associated with the NSF-capable router as stale; however, it continues to use these routes to make forwarding decisions for a set period of time. This functionality means that no packets are lost while the newly active RP is waiting for convergence of the routing information with its BGP peers.
After a failover event occurs, the NSF-capable router reestablishes the session with the BGP peer. In establishing the new session, it sends a new graceful restart message that identifies the NSF-capable router as having restarted.
At this point, the routing information is exchanged between the two BGP peers. Once this exchange is complete, the NSF-capable device uses the newly received routing information to update the RIB and the Forwarding Information Base (FIB) with the new forwarding information. The NSF-aware device uses the network information to remove stale routes from its BGP table. The BGP protocol is then fully converged.
If a BGP peer does not support the graceful restart capability, it will ignore the graceful restart capability in an OPEN message but will establish a BGP session with the NSF-capable device. This functionality will allow interoperability with non-NSF-aware BGP peers (and without NSF functionality), but the BGP session with non-NSF-aware BGP peers will not be graceful restart-capable.
QUESTION 19
Refer to the exhibit. Which configuration is missing to complete the configuration task of enabling BFD with the 192.168.1.1 EBGP peer?
“First Test, First Pass” – www.lead2pass.com 9 Cisco 642-885 Exam

A. bfd fast-detect also needs to be enabled globally under router bgp 64500 RP/0/RSP0/CPU0:P1(config-bgp)#bfd fast-detect
B. bfd fast-detect also needs to be enabled for the address-family under address-family ipv4 unicast RP/0/ RSP0/CPU0:P1(config-bgp-af)#bfd fast-detect
C. bfd fast-detect also needs to be enabled for the 192.168.1.1 neighbor under neighbor 192.168.1.1 RP/0/RSP0/CPU0:P1(config-bgp-nbr)#bfd fast-detect
D. bfd fast-detect also needs to be enabled for the 192.168.1.1 neighbor address-family under neighbor
192.168.1.1 address-family ipv4 unicast
RP/0/RSP0/CPU0:P1(config-bgp-nbr-af)#bfd fast-detect

E. bfd fast-detect also needs to be enabled globally on the router RP/0/RSP0/CPU0:P1(config)#bfd fast-detect

Correct Answer: C Section: (none) Explanation
Explanation/Reference: QUESTION 20

Which two features are used to provide high availability multicast? (Choose two.)
A. BFD
B. NSF/SSO
C. PIM NSR
D. PIM triggered join
E. IGMP triggered report
F. MSDP

Correct Answer: BD Section: (none) Explanation
Explanation/Reference:
Triggered joins are sent when the primary or the secondary RPF information changes. No RPF change prunes are sent for MoFRR streams.
mofrr
To perform a fast convergence (multicast-only fast reroute, or MoFRR) of specified routes/flows when a failure is detected on one of multiple equal-cost paths between the router and the source, use the mofrr command under PIM configuration mode.

mofrr rib acl_name no rib acl_name

 

Preparing Cisco 642-885 exam is not difficult now.You can prepare from Cisco 642-885 Certification or Cisco 642-885 dumps.Here we have mentioned some sample questions.You can use our Cisco 642-885 study material notes for test preparation.Latest Cisco 642-885 study material available.

Author

Back to Top