Cisco 642-885 Online Practice Questions and Exam Preparation

Cisco 642-885 Online Questions & Answers

• Question 51:

  Which command configures a Source Specific Multicast on a Cisco IOS XR router?

  A. configure multicast-routing address-family ipv4 interface all enable exit router igmp version 3 commit
  B. configure multicast-routing address-family ipv4 interface all enable exit router igmp version 2 commit
  C. configure multicast-routing address-family ipv4 interface all enable exit router igmp version 1 commit
  D. configure interface all enable exit router igmp version 3 commit
  A. configure multicast-routing address-family ipv4 interface all enable exit router igmp version 3 commit

• Question 52:

  Which Cisco IOS XR command sets successfully configure a value of 20 for the advertisement- interval?

  A. RP/0/RSP0/CPU0:routerconfig)# router bgp 65512 RP/0/RSP0/CPU0:router(config-bgp)# session-group test RP/0/RSP0/CPU0:router(config-bgp-sngrp)# advertisement-interval 20 RP/0/RSP0/CPU0:router (config-bgp-sngrp)# exit RP/0/RSP0/CPU0:router(config-bgp)# neighbor-group test RP/0/RSP0/CPU0:router(config-bgp-nbrgrp)# advertisement-interval 25 RP/0/RSP0/CPU0:router (config-bgp-nbrgrp)# exit RP/0/RSP0/CPU0:router(config-bgp)# exit RP/0/RSP0/CPU0:router(config-bgp)# neighbor 192.168.1.1 RP/0/RSP0/CPU0:router(config-bgp-nbr)# remote-as 65513 RP/0/RSP0/CPU0:router(config-bgpnbr)# use session-group test RP/0/RSP0/CPU0:router(config-bgp-nbr)# use neighbor-group test
  B. RP/0/RSP0/CPU0:routerconfig)# router bgp 65512 RP/0/RSP0/CPU0:router(config-bgp)# session-group test RP/0/RSP0/CPU0:router(config-bgp-sngrp)# ebgp-multihop 2 RP/0/RSP0/CPU0:router(config-bgpsngrp)# exit RP/0/RSP0/CPU0:router(config-bgp)# neighbor-group test RP/0/RSP0/CPU0:router(config-bgp-nbrgrp)# advertisement-interval 20 RP/0/RSP0/CPU0:router (config-bgp-nbrgrp)# exit RP/0/RSP0/CPU0:router(config-bgp)# exit RP/0/RSP0/CPU0:router(config-bgp)# neighbor 192.168.1.1 RP/0/RSP0/CPU0:router(config-bgp-nbr)# remote-as 65513 RP/0/RSP0/CPU0:router(config-bgpnbr)# use session-group test RP/0/RSP0/CPU0:router(config-bgp-nbr)# use neighbor-group test
  C. RP/0/RSP0/CPU0:routerconfig)# router bgp 65512 RP/0/RSP0/CPU0:router(config-bgp)# session-group test RP/0/RSP0/CPU0:router(config-bgp-sngrp)# exit RP/0/RSP0/CPU0:router(config-bgp)# neighbor-group test RP/0/RSP0/CPU0:router(config-bgp-nbrgrp)# exit RP/0/RSP0/CPU0:router(config-bgp)# exit RP/0/RSP0/CPU0:router(config-bgp)# neighbor 192.168.1.1 RP/0/RSP0/CPU0:router(config-bgp-nbr)# remote-as 65513 RP/0/RSP0/CPU0:router(config-bgpnbr)# use session-group test RP/0/RSP0/CPU0:router(config-bgp-nbr)# use neighbor-group test
  D. RP/0/RSP0/CPU0:routerconfig)# router bgp 65512 RP/0/RSP0/CPU0:router(config-bgp)# session-group test RP/0/RSP0/CPU0:router(config-bgp-sngrp)# advertisement-interval 25 RP/0/RSP0/CPU0:router (config-bgp-sngrp)# exit RP/0/RSP0/CPU0:router(config-bgp)# neighbor-group test RP/0/RSP0/CPU0:router(config-bgp-nbrgrp)# advertisement-interval 20 RP/0/RSP0/CPU0:router (config-bgp-nbrgrp)# exit RP/0/RSP0/CPU0:router(config-bgp)# exit RP/0/RSP0/CPU0:router(config-bgp)# neighbor 192.168.1.1 RP/0/RSP0/CPU0:router(config-bgp-nbr)# remote-as 65513 RP/0/RSP0/CPU0:router(config-bgpnbr)# use session-group test RP/0/RSP0/CPU0:router(config-bgp-nbr)# use neighbor-group test
  A. RP/0/RSP0/CPU0:routerconfig)# router bgp 65512 RP/0/RSP0/CPU0:router(config-bgp)# session-group test RP/0/RSP0/CPU0:router(config-bgp-sngrp)# advertisement-interval 20 RP/0/RSP0/CPU0:router (config-bgp-sngrp)# exit RP/0/RSP0/CPU0:router(config-bgp)# neighbor-group test RP/0/RSP0/CPU0:router(config-bgp-nbrgrp)# advertisement-interval 25 RP/0/RSP0/CPU0:router (config-bgp-nbrgrp)# exit RP/0/RSP0/CPU0:router(config-bgp)# exit RP/0/RSP0/CPU0:router(config-bgp)# neighbor 192.168.1.1 RP/0/RSP0/CPU0:router(config-bgp-nbr)# remote-as 65513 RP/0/RSP0/CPU0:router(config-bgpnbr)# use session-group test RP/0/RSP0/CPU0:router(config-bgp-nbr)# use neighbor-group test

• Question 53:

  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
  C. The [ ] indicates the configuration was not inherited from a group

  ---

  : show bgp neighbors Use the show bgp neighbors command to display information about the BGP configuration for neighbors. ꞏUse 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. ꞏUse 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:

  

• Question 54:

  Which command set implements BGP support for NSF/SSO on Cisco IOS XE between a PE and a route reflector?

  A. On RR: router bgp 300 no synchronization bgp log-neighbor-changes bgp graceful-restart restart-time 120 bgp graceful-restart stalepath-time 360 bgp graceful-restart neighbor 10.20.20.2 remote-as 200 neighbor 10.20.20.2 update-source Loopback0 no auto-summary ! address-family vpnv4 neighbor 10.20.20.2 activate neighbor 10.20.20.2 send-community both neighbor 10.20.20.2 route-reflector-client exit-address-family On PE: router bgp 300 no synchronization bgp log-neighbor-changes bgp graceful-restart restart-time 120 bgp graceful-restart stalepath-time 360 bgp graceful-restart neighbor 10.20.20.1 remote-as 300 neighbor 10.20.20.1 update-source Loopback0 no auto-summary ! address-family vpnv4 neighbor 10.20.20.1 activate neighbor 10.20.20.1 send-community both exit-address-family !
  B. On RR: router bgp 300 no synchronization bgp log-neighbor-changes bgp graceful-restart restart-time 120 bgp graceful-restart stalepath-time 360 bgp graceful-restart neighbor 10.20.20.2 remote-as 200 neighbor 10.20.20.2 update-source Loopback0 no auto-summary ! address-family vpnv4 neighbor 10.20.20.2 activate neighbor 10.20.20.2 send-community both neighbor 10.20.20.2 route-reflector-client exit-address-family On PE: router bgp 300 no synchronization bgp log-neighbor-changes neighbor 10.20.02.1 remote-as 300 neighbor 10.20.20.1 update-source Loopback0 no auto-summary ! address-family vpnv4 neighbor 10.20.20.1 activate neighbor 10.20.20.1 send-community both exit-address-family !
  C. On RR: router bgp 300 no synchronization bgp log-neighbor-changes bgp graceful-restart restart-time 120 bgp graceful-restart stalepath-time 360 bgp graceful-restart neighbor 10.20.20.2 remote-as 200 neighbor 10.20.20.2 update-source Loopback0 no auto-summary ! address-family vpnv4 neighbor 10.20.20.2 activate neighbor 10.20.20.2 send-community both neighbor 10.20.20.2 route-reflector-client exit-address-family On PE: router bgp 300 no synchronization bgp log-neighbor-changes neighbor 10.20.20.1 remote-as 300 neighbor 10.20.20.1 update-source Loopback0 neighbor 10.20.20.1 ha-mode sso no auto-summary ! address-family vpnv4 neighbor 10.20.20.1 activate neighbor 10.20.20.1 send-community both exit-address-family !
  D. On RR: router bgp 300 no synchronization bgp log-neighbor-changes neighbor 10.20.20.2 remote-as 200 neighbor 10.20.20.2 update-source Loopback0 neighbor 10.20.20.2 ha-mode sso no auto-summary ! address-family vpnv4 neighbor 10.20.20.2 activate neighbor 10.20.20.2 send-community both neighbor 10.20.20.2 route-reflector-client exit-address-family On PE: router bgp 300 no synchronization bgp log-neighbor-changes neighbor 10.20.20.1 remote-as 300 neighbor 10.20.20.1 update-source Loopback0 neighbor 10.20.20.1 ha-mode sso no auto-summary ! address-family vpnv4 neighbor 10.20.20.1 activate neighbor 10.20.20.1 send-community both exit-address-family !
  E. On RR: router bgp 300 no synchronization bgp log-neighbor-changes neighbor 10.20.20.2 remote-as 200 neighbor 10.20.20.2 update-source Loopback0 no auto-summary ! address-family vpnv4 neighbor 10.20.20.2 activate neighbor 10.20.20.2 send-community both neighbor 10.20.20.2 route-reflector-client exit-address-family On PE: router bgp 300 no synchronization bgp log-neighbor-changes bgp graceful-restart restart-time 120 bgp graceful-restart stalepath-time 360 bgp graceful-restart neighbor 10.20.20.1 remote-as 300 neighbor 10.20.20.1 update-source Loopback0 no auto-summary ! address-family vpnv4 neighbor 10.20.20.1 activate neighbor 10.20.20.1 send-community both exit-address-family !
  A. On RR: router bgp 300 no synchronization bgp log-neighbor-changes bgp graceful-restart restart-time 120 bgp graceful-restart stalepath-time 360 bgp graceful-restart neighbor 10.20.20.2 remote-as 200 neighbor 10.20.20.2 update-source Loopback0 no auto-summary ! address-family vpnv4 neighbor 10.20.20.2 activate neighbor 10.20.20.2 send-community both neighbor 10.20.20.2 route-reflector-client exit-address-family On PE: router bgp 300 no synchronization bgp log-neighbor-changes bgp graceful-restart restart-time 120 bgp graceful-restart stalepath-time 360 bgp graceful-restart neighbor 10.20.20.1 remote-as 300 neighbor 10.20.20.1 update-source Loopback0 no auto-summary ! address-family vpnv4 neighbor 10.20.20.1 activate neighbor 10.20.20.1 send-community both exit-address-family !

• Question 55:

  

  

  

  Which router Is configured as the RPforthe 234.1.1.1 multicast group and which Is the multicast source that is currently sending traffic to the 234.1.1.1 multicast group? (Choose two.)

  A. CE5
  B. PE5
  C. PE6
  D. 10.5.10.1
  E. 10.5.1.1
  F. 192.168.156.60
  C. PE6
  E. 10.5.1.1

  ---

  #show ip mroute 234.1.1.1 #show ip route

• Question 56:

  Which three statements regarding NAT64 operations are correct? (Choose three.)

  A. With stateful NAT64, many IPv6 address can be translated into one IPv4 address, thus IPv4 address conservation is achieved
  B. Stateful NAT64 requires the use of static translation slots so IPv6 hosts and initiate connections to IPv4 hosts.
  C. With stateless NAT64, the source and destination IPv4 addresses are embedded in the IPv6 addresses
  D. NAT64 works in conjunction with DNS64
  E. Both the stateful and stateless NAT64 methods will conserve IPv4 address usage
  A. With stateful NAT64, many IPv6 address can be translated into one IPv4 address, thus IPv4 address conservation is achieved
  C. With stateless NAT64, the source and destination IPv4 addresses are embedded in the IPv6 addresses
  D. NAT64 works in conjunction with DNS64

  ---

  Stateful NAT64-Network Address and Protocol Translation from IPv6 Clients to IPv4 Servers Stateful NAT64 multiplexes many IPv6 devices into a single IPv4 address. It can be assumed that this technology will be used mainly where IPv6-only networks and clients (ie. Mobile handsets, IPv6 only wireless, etc...) need access to the IPv4 internet and its services. The big difference with stateful NAT64 is the elimination of the algorithmic binding between the IPv6 address and the IPv4 address. In exchange, state is created in the NAT64 device for every flow. Additionally, NAT64 only supports IPv6-initiated flows. Unlike stateless NAT64, stateful NAT64 does `not' consume a single IPv4 address for each IPv6 device that wants to communicate to the IPv4 Internet. More practically this means that many IPv6-only users consume only single IPv4 address in similar manner as IPv4-to-IPv4 network address and port translation works. This works very well if the connectivity request is initiated from the IPv6 towards the IPv4 Internet. If an IPv4-only device wants to speak to an IPv6-only server for example, manual configuration of the translation slot will be required, making this mechanism less attractive to provide IPv6 services towards the IPv4 Internet. DNS64 is usually also necessary with a stateful NAT64, and works the same with both stateless and stateful NAT64 Stateless NAT64-Stateless translation between IPv4 and IPv6 RFC6145 (IP/ICMP Translation Algorithm) replaces RFC2765 (Stateless IP/ICMP Translation Algorithm (SIIT)) and provides a stateless mechanism to translate a IPv4 header into an IPv6 header and vice versa. Due to the stateless character this mechanism is very effective and highly fail safe because more as a single- or multiple translators in parallel can be deployed and work all in parallel without a need to synchronize between the translation devices.

  The key to the stateless translation is in the fact that the IPv4 address is directly embedded in the IPv6 address. A limitation of stateless NAT64 translation is that it directly translates only the IPv4 options that have direct IPv6 counterparts, and that it does not translate any IPv6 extension headers beyond the fragmentation extension header; however, these limitations are not significant in practice.

  With a stateless NAT64, a specific IPv6 address range will represent IPv4 systems within the IPv6 world. This range needs to be manually configured on the translation device. Within the IPv4 world all the IPv6 systems have directly correlated IPv4 addresses that can be algorithmically mapped to a subset of the service provider's IPv4 addresses. By means of this direct mapping algorithm there is no need to keep state for any translation slot between IPv4 and IPv6. This mapping algorithm requires the IPv6 hosts be assigned specific IPv6 addresses, using manual configuration or DHCPv6.

  Stateless NAT64 will work very successful as proven in some of the largest networks, however it suffers from some an important side-effect: Stateless NAT64 translation will give an IPv6-only host access to the IPv4 world and vice versa, however it consumes an IPv4 address for each IPv6-only device that desires translation -- exactly the same as a dual-stack deployment. Consequentially, stateless NAT64 is no solution to address the ongoing IPv4 address depletion. Stateless NAT64 is a good tool to provide Internet servers with an accessible IP address for both IPv4 and IPv6 on the global Internet. To aggregate many IPv6 users into a single IPv4 address, stateful NAT64 is required. NAT64 are usually deployed in conjunction with a DNS64. This functions similar to, but different than, DNS-ALG that was part of NAT-PT. DNS64 is not an ALG; instead, packets are sent directly to and received from the DNS64's IP address. DNS64 can also work with DNSSEC (whereas DNS-ALG could not).

• Question 57:

  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
  A. The BGP table will be examined and verified more frequently
  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

  ---

  

• Question 58:

  Which two methods represent IPv6 tunneling implementations? (Choose two.)

  A. IPv6 over GRE tunneling
  B. manually configured tunnels
  C. automatic tunnels
  D. 6to4 tunneling
  E. IPv6 over an IPv4 tunnel over MPLS
  B. manually configured tunnels
  C. automatic tunnels

• Question 59:

  When implementing source-based remote-triggered black hole filtering, which two configurations are required on the edge routers that are not the signaling router? (Choose two.)

  A. A static route to a prefix that is not used in the network with a next hop set to the Null0 interface
  B. A static route pointing to the IP address of the attacker
  C. uRPF on all external facing interfaces at the edge routers
  D. Redistribution into BGP of the static route that points to the IP address of the attacker
  E. A route policy to set the redistributed static routes with the no-export BGP community
  A. A static route to a prefix that is not used in the network with a next hop set to the Null0 interface
  C. uRPF on all external facing interfaces at the edge routers

  ---

  Source-Based RTBH Filtering

  With destination-based black holing, all traffic to a specific destination is dropped after the black hole has been activated, regardless of where it is coming from.

  Obviously, this could include legitimate traffic destined for the target. Source-based black holes provide the ability to drop traffic at the network edge based on a

  specific source address or range of source addresses.

  If the source address (or range of addresses) of the attack can be identified (spoofed or not), it would be better to drop all traffic at the edge based on the source

  address, regardless of the destination address. This would permit legitimate traffic from other sources to reach the target. Implementation of source-based black

  hole filtering depends on Unicast Reverse Path Forwarding (uRPF), most often loose mode uRPF.

  Loose mode uRPF checks the packet and forwards it if there is a route entry for the source IP of the incoming packet in the router forwarding information base

  (FIB). If the router does not have an FIB entry for the source IP address, or if the entry points to a null interface, the Reverse Path Forwarding (RPF) check fails

  and the packet is dropped, as shown in Figure 2. Because uRPF validates a source IP address against its FIB entry, dropping traffic from specific source

  addresses is accomplished by configuring loose mode uRPF on the external interface and ensuring the RPF check fails by inserting a route to the source with a

  next hop of Null0. This can be done by using a trigger device to send IBGP updates. These updates set the next hop for the source IP to an unused IP address

  that has a static entry at the edge, setting it to null as shown in Figure 2.

  

• Question 60:

  

  

  On the PE5 router, which statement Is correct regarding the learned BGP prefixes?

  A. The 209.165.201.0/27 prefix is received from the 10.0.1.1 IBGP peer which is a route reflector
  B. The 172.16.66.0/24 prefix BGP next-hop points to the route reflector
  C. All prefixes learned on PE5 has the default local prefernce value
  D. The 209.165.202.128/27 prefix is originated by the 10.0.1.1 IBGP peer
  C. All prefixes learned on PE5 has the default local prefernce value

  ---

  #show ip bgp -- check i tag for PE5