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QUESTION 101
The core routers within a transit AS are running both IBGP and IGP. The edge routers within the transit AS are using the next-hop-self option to establish the IBGP sessions. What can be implemented to improve the routing performance to all external prefixes?
A. enable route redistribution from BGP into IGP
B. disable BGP synchronization on all the core routers
C. enable CEF on all the core and edge routers
D. enable route redistribution from IGP into BGP
E. use route reflectors within the core
Answer: C
QUESTION 102
What is a key benefit of BGP dynamic update peer groups?
A. Routing updates to the same destination are grouped to increase BGP efficiency.
B. Newly configured BGP neighbors have peer group template configurations dynamically applied.
C. Dynamic update groups use iBGP neighbor information to automatically calculate route reflector cluster
configurations.
D. Neighbors in a peer group are no longer required to share the same outbound routing policies.
E. BGP configurations are automatically optimized by routers which dynamically create BGP peer groups.
Answer: D
QUESTION 103
What are two characteristics of BGP confederations? (Choose two.)
A. All routers within the BGP confederation must support BGP confederations.
B. The member AS numbers used within the confederation are visible from outside the confederation.
C. An Intra-Confederation EBGP session behaves like an EBGP session when propagating routing updates.
D. Intra-Confederation EBGP neighbors must be directly connected or ebgp-multihop must be configured.
Answer: AD
QUESTION 104
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
Answer: BC
QUESTION 105
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.
Answer: AE
QUESTION 106
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
E. Which RP to use from a set of candidate RPs in the RP set
Answer: E
QUESTION 107
Refer to the topology diagram shown in the exhibit and the partial configurations shown below.
Once the attack from 209.165.201.144/28 to 209.165.202.128/28 has been detected, which additional configurations are required on the P1 IOS-XR router to implement source-based remote-triggered black hole filtering?
!
router bgp 123
address-family ipv4 unicast
redistribute static route-policy test
!
A. router static
address-family ipv4 unicast
209.165.202.128/28 null0 tag 666
192.0.2.1/32 null0 tag 667
!
route-policy test
if tag is 666 then
set next-hop 192.0.2.1
endif
if tag is 667 then
set community (no-export)
endif
end-policy
!
B. router static
address-family ipv4 unicast
209.165.201.144/28 null0 tag 666
192.0.2.1/32 null0 tag 667
!
route-policy test
if tag is 666 then
set next-hop 192.0.2.1
endif
if tag is 667 then
set community (no-export)
endif
end-policy
!
C. router static
address-family ipv4 unicast
209.165.201.144/28 null0 tag 666
192.0.2.1/32 null0
!
route-policy test
if tag is 666 then
set next-hop 192.0.2.1
set community (no-export)
endif
end-policy
D. router static
address-family ipv4 unicast
209.165.202.128/28 null0 tag 666
192.0.2.1/32 null0
!
route-policy test
if tag is 666 then
set next-hop 192.0.2.1
set community (no-export)
endif
end-policy
!
Answer: C
Explanation:
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 108
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
Answer: ACDE
Explanation:
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 MSDPenabled 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 109
In which three cases is a dual-stack IPv6/IPv4 router required? (Choose three.)
A. tunnel endpoint routers in the case of IPv6 over GRE
B. transit routers in case of an IPv6 over GRE implementation
C. 6to4 implementation border routers
D. 6to4 implementation border and neighboring routers
E. PE routers in case of an IPv6 over IPv4 tunnel over MPLS implementation
F. PE and P routers in case of an IPv6 over IPv4 tunnel over MPLS implementation
Answer: ACE
QUESTION 110
Which command set is used to implement an IPv6 PIM with the global scope embedded RP address of 2001:DB8::1 on a Cisco IOS XE router?
A. ipv6 unicast-routing
ipv6 multicast-routing
ipv6 pim rp-address 2001:DB8::1 bidir
B. ipv6 multicast-routing
ipv6 pim rp-address 2001:DB8::1
C. ipv6 unicast-routing
ipv6 multicast-routing
ipv6 pim rp-address FF7E:0120:2001:DB8:1111::4321
D. ipv6 unicast-routing
ipv6 multicast-routing
int Lo0
ipv6 mld join-group FF7E:0120:2001:DB8:1111::4321
E. ipv6 unicast-routing
ipv6 multicast-routing
int Lo0
ipv6 mld join-group FF75:0120:2001:DB8:1111::4321
Answer: D
QUESTION 111
Drag and Drop Question
Answer:
QUESTION 112
Given the IPv6 address of 2001:0DB8::1:800:200E:88AA, what will be its corresponding the solicited-node multicast address?
A. FF01::1:200E:88AA
B. FF01::1:FF0E:88AA
C. FF01:0DB8::1:800:200E:88AA
D. FF02::1:FF0E:88AA
E. FF02::1:200E:88AA
F. FF02:0DB8::1:800:200E:88AA
Answer: D
Explanation:
IPv6 nodes (hosts and routers) are required to join (receive packets destined for) the following multicast groups:
All-nodes multicast group FF02:0:0:0:0:0:0:1 (scope is link-local)
Solicited-node multicast group FF02:0:0:0:0:1:FF00:0000/104 for each of its assigned unicast and anycast addresses
IPv6 routers must also join the all-routers multicast group FF02:0:0:0:0:0:0:2 (scope is link- local).
The solicited-node multicast address is a multicast group that corresponds to an IPv6 unicast or anycast address. IPv6 nodes must join the associated solicited-node multicast group for every unicast and anycast address to which it is assigned. The IPv6 solicited- node multicast address has the prefix FF02:0:0:0:0:1:
FF00:0000/104 concatenated with the 24 low-order bits of a corresponding IPv6 unicast or anycast address (see Figure 2). For example, the solicited-node multicast address corresponding to the IPv6 address 2037::01:800:200E:8C6C is FF02::1:FF0E:8C6C. Solicited-node addresses are used in neighbor solicitation messages
QUESTION 113
Referring to the topology diagram show in the exhibit,
which three statements are correct regarding the BGP routing updates? (Choose three.)
A. The EBGP routing updates received by R1 from R5 will be propagated to the R2, R4, and R7 routers
B. The EBGP routing updates received by R3 from R6 will be propagated to the R2 and R4 routers
C. The EBGP routing updates received by R1 from R5 will be propagated to the R2 and R4 routers
D. The IBGP routing updates received by R3 from R2 will be propagated to the R6 router
E. The IBGP routing updates received by R2 from R1 will be propagated to the R3 router
F. The IBGP routing updates received by R1 from R4 will be propagated to the R5, R7, and R2 routers
Answer: ABD
QUESTION 114
A CRS router that runs Cisco IOS XR has dual routing processors installed. Which solution should be implemented to prevent OSPF adjacency flapping if the primary routing processor fails?
A. NSR
B. OSPF Fast Timers
C. OSPF RE Sync
D. router msdp
E. NSF
Answer: A
QUESTION 115
After configuring the tunnel interface as shown in the exhibit, no IPv6 traffic is passed over the IPv4 network.
Which additional configuration is required to pass the IPv6 traffic over the IPv4 network?
A. Configure an IPv4 address on the tunnel0 interface
B. Configure an IPv6 static route to send the required IPv6 traffic over the tunnel0 interface
C. The tunnel destination should be pointing to an IPv6 address instead of an IPv4 address
D. The tunnel0 interface IPv6 address must use the 2002:://16 prefix
Answer: B
QUESTION 116
Which two options are characteristics ofconfiguration templates used by Cisco IOS XRto optimize BGP peering implementations? (Choose two.)
A. Session groups are used to inherit address family-specific configurations.
B. Cisco IOS XR provides by default a session group operating with all the supported address families.
C. Session groups are used to inherit address family-independent configurations.
D. Session groups can be included within a neighbor group.
E. Session groups can include neighbor groups.
Answer: CD
QUESTION 117
In Cisco IOS-XR, the ttl-security command is configured under which configuration mode?
A. RP/0/RSP0/CPU0:P2(config)#
B. RP/0/RSP0/CPU0:P2(config-bgp)#
C. RP/0/RSP0/CPU0:P2(config-bgp-nbr)#
D. RP/0/RSP0/CPU0:P2(config-bgp-af)#
E. RP/0/RSP0/CPU0:P2(config-bgp-nbr-af)#
Answer: C
Explanation:
http://packetlife.net/blog/2009/nov/23/understanding-bgp-ttl-security/
QUESTION 118
Which multicast routing protocol is most optimal for supporting many-to-many multicast applications?
A. PIM-SM
B. PIM-BIDIR
C. MP-BGP
D. DVMRP
E. MSDP
Answer: B
Explanation:
PIM-Bidirectional Operations
PIM Bidirectional (BIDIR) has one shared tree from sources to RP and from RP to receivers.
This is unlike the PIM-SM, which is unidirectional by nature with multiple source trees – one per (S, G) or a shared tree from receiver to RP and multiple SG trees from RP to sources.
Benefits of PIM BIDIR are as follows:
As many sources for the same group use one and only state (*, G), only minimal states are required in each router.
No data triggered events.
Rendezvous Point (RP) router not required.
The RP address only needs to be a routable address and need not exist on a physical device.
QUESTION 119
Refer to the exhibit. Which option is the function of designing a hub and spoke confederation?
A. allows transit backbone area 66000 to be a blackhole for non-transit ASs
B. reduces the iBGP mesh, iBGP mesh will be in sub non-transit ASs
C. increases eBGP sessions between the confederation sub ASs
D. allows transit backbone area and non-transit ASs to run the same IGP
Answer: B
QUESTION 120
When implementing high-availability stateful switchover BGP routing, in which situation would Cisco NSR be required?
A. On the PE routers connecting to the CE routers which are not NSF aware or are not NSF capable
B. On the PE routers connecting to the CE routers which support graceful restart
C. On the PE routers connecting to the CE routers which are incapable of performing stateful switchover operations because the CE routers are only NSF aware but not NSF capable
D. On the PE routers connecting to the CE routers which are incapable of performing stateful switchover operations because the CE routers are only NSF capable but not NSF aware
E. On the service provider core P routers which are also NSF aware
F. On the service provider core P routers which are also NSF capable
Answer: A
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