Cisco 642-885 Online Practice Questions and Exam Preparation

Cisco 642-885 Online Questions & Answers

• Question 31:

  Which two commands can be used to implement a valid Cisco IOS XE IPv6 static tunnel configuration? (Choose two.)

  A. interface Tunnel100 ipv6 enable ipv6 address 2001:DB8::1/128 tunnel destination 209.165.201.2 tunnel mode ipv6ip 6to4
  B. interface Tunnel100 ipv6 enable ipv6 address 2001:DB8::1/128 tunnel source Ethernet 0/1 tunnel destination 209.165.201.2 tunnel mode gre ip
  C. interface Tunnel 100 ipv6 enable ip address 209.165.201.2 tunnel source Loopback 0 tunnel mode ipv6ip 6to4
  D. interface Tunnel100 ipv6 enable ipv6 address 2001:DB8::1/128 tunnel source Ethernet 0/1 tunnel destination 209.165.201.2 tunnel mode isatap
  E. interface Tunnel100 ipv6 enable ipv6 address 2001:DB8::1/128 tunnel source Ethernet 0/1 tunnel destination 209.165.201.2 tunnel mode auto-tunnel
  F. interface Tunnel100 ipv6 enable ipv6 address 2001:DB8::1/128 tunnel source Ethernet 0/1 tunnel destination 209.165.201.2 tunnel mode ipv6ip
  B. interface Tunnel100 ipv6 enable ipv6 address 2001:DB8::1/128 tunnel source Ethernet 0/1 tunnel destination 209.165.201.2 tunnel mode gre ip
  F. interface Tunnel100 ipv6 enable ipv6 address 2001:DB8::1/128 tunnel source Ethernet 0/1 tunnel destination 209.165.201.2 tunnel mode ipv6ip

• Question 32:

  A network engineer of an ISP using Cisco IOS XR routers wants to limit the number of prefixes that BGP peers can accept. To accomplish this task, the command maximum-prefix 1000 is used. Which two results of this configuration are expected? (Choose two.)

  A. A warning message displays by default when 750 prefixes are received.
  B. A warning message displays by default when 850 prefixes are received.
  C. A BGP peer resets when it receives 1001 prefixes.
  D. A BGP peer resets when it receives 1000 prefixes.
  E. A BGP peer ceases when it receives 1001 prefixes.
  F. A BGP peer ceases when it receives 1000 prefixes.
  G. The BGP peer tries to reestablish the session after one minute.
  A. A warning message displays by default when 750 prefixes are received.
  E. A BGP peer ceases when it receives 1001 prefixes.

• Question 33:

  Refer to the Cisco IOS-XR configuration exhibit.

  

  The Cisco IOS-XR router is unable to establish any PIM neighbor relationships. What is wrong with the configuration?

  A. The configuration is missing: interface gi0/0/0/0 ip pim sparse-mode interface gi0/0/0/1 ip pim sparse-mode interface loopback0 ip pim sparse-mode
  B. The configuration is missing: multicast-routing address-family ipv4 interface gi0/0/0/0 enable interface gi0/0/0/1 enable
  C. The auto-rp scoping configurations should be set to 1 not 16
  D. The RP address has not been configured using the rp-address router PIM configuration command
  E. PIM defaults to dense mode operations only, so PIM sparse mode must be enabled using the pim sparse-mode router PIM configuration command
  B. The configuration is missing: multicast-routing address-family ipv4 interface gi0/0/0/0 enable interface gi0/0/0/1 enable

• Question 34:

  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
  A. The MSDP peers are also typically the RPs in respective routing domains.
  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

• Question 35:

  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
  B. Use MSDP to enable the RPs from different domains to exchange information about active multicast sources
  D. Noncongruent unicast and multicast topologies can be supported using multiprotocol BGP

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  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.ht ml

  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 36:

  Refer to the exhibit. R2 cannot to learn RP information from XR3. Which issue is the source of the problem?

  

  A. XR3 is not the DR.
  B. Multicast routing is not enabled on the XR3 Giga0/0/0/0 interface.
  C. R2 is learning the RP address via non-IGP routing protocol.
  D. Multicast routing is not enabled on the XR3 Loopback0 interface.
  E. BGP IPv4 MDT address family is not enabled on XR3.
  D. Multicast routing is not enabled on the XR3 Loopback0 interface.

• Question 37:

  Which two actions result when a network administrator attempts to ping an IPv6 host on the LAN? (Choose two.)

  A. ARP is used to determine the MAC address of the destination host.
  B. Neighbor Discovery is used to determine the MAC address of the destination host.
  C. Neighbor Solicitation messages are sent out by the source host to determine the data link-layer address of the destination host.
  D. Neighbor Advertisement messages are sent by the source host to announce its presence on the local link.
  E. Router Solicitation messages are sent out on a specific multicast address to request the data link-layer address of the target device.
  F. Router Solicitation messages are sent to the local router on the network segment to request data link-layer information about the destination host.
  B. Neighbor Discovery is used to determine the MAC address of the destination host.
  C. Neighbor Solicitation messages are sent out by the source host to determine the data link-layer address of the destination host.

• Question 38:

  The IPv6 2002::/16 prefix is used in which kind of implementations?

  A. 6 RD
  B. 6 to 4
  C. NAT 64
  D. IPv6 Multicast
  B. 6 to 4

• Question 39:

  A network engineer must configure a Cisco IOS XR router with BGP dampening. Which configuration meets these parameters?

  A. router bgp 60 bgp dampening
  B. router bgp 60 neighbor 10.0.0.2 bgp dampening
  C. router bgp 60 address-family ipv4 unicast bgp dampening
  D. route-policy dampening_specific drop ! router bgp 60 address-family ipv4 unicast bgp dampening route-policy dampening_specific
  E. router bgp 60 address-family ipv4 bgp dampening
  C. router bgp 60 address-family ipv4 unicast bgp dampening

• Question 40:

  What must occur before an (S,G) entry can be populated in the multicast routing table?

  A. The (*,G) entry must have timed out
  B. The (*,G) entry OIL must be null
  C. The router must be directly connected to the multicast source
  D. The parent (*,G) entry must be created first
  D. The parent (*,G) entry must be created first