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QUESTION 81
An engineer is working for a service provider who is strategically important to the Internet data traffic. The CTO is promoting a core infrastructure upgrade to connect via optical links network service providers. Which three concerns must be addressed while planning the new BGP features and functionalities? (Choose three.)
A. BGP suboptimal routing
B. IPv4 exhaustion
C. routers and switches hardware capabilities
D. route dampening of current customers
E. multihoming policies of new customers
F. IGP reconvergence time on the inter-AS links
G. BGP blackholing when acting as transit autonomous system
Answer: ACG
QUESTION 82
When implementing LDP, what is liberal label retention mode?
A. To reduce the convergence time, the LSR will retain all the received labels in its LIB even if all the neighbor LSRs go down temporary
B. The LSR can assign it’s own label for each destination network even though it has not been assigned a next hop label from the neighbor LSR
C. The LSR will store the label received from the downstream LSRs in its LIB even if the downstream LSRs are not the next hop for the destination
D. The LSR will not perform PHP if it is operating in liberal label retention mode
Answer: C
Explanation:
By default, LDP accepts labels (as remote bindings) for all prefixes from all peers. LDP operates in liberal label retention mode, which instructs LDP to keep remote bindings from all peers for a given prefix. For security reasons, or to conserve memory, you can override this behavior by configuring label binding acceptance for set of prefixes from a given peer.
The ability to filter remote bindings for a defined set of prefixes is also referred to as LDP inbound label filtering
QUESTION 83
Which option can a network specialist use to configure connected route redistribution inside VRF “TEST” on Cisco IOS XR and allow only the prefix 10.10.10.0/24?
A. route-policy ALLOW-CONN
if destination in PERMIT_PREFIX then
pass
else
drop
end-policy
prefix-set PERMIT_PREFIX
10.10.10.0/24
end-set
router bgp 65000
vrf TEST
rd 65000:10000
address-family ipv4 unicast
redistribute connected route-policy ALLOW-CONN
B. route-policy ALLOW-CONN
if source in PERMIT_PREFIX then
pass
else
drop
end-policy
prefix-set PERMIT_PREFIX
10.10.10.0/24
end-set
router bgp 65000
vrf TEST
rd 65000:10000
address-family ipv4 unicast
redistribute connected route-policy ALLOW-CONN
C. route-policy ALLOW-CONN
if protocol is connected and source in PERMIT_PREFIX then pass
else
drop
end-policy
prefix-set PERMIT_PREFIX
10.10.10.0/24
end-set
router bgp 65000
vrf TEST
rd 65000:10000
address-family ipv4 unicast
redistribute connected route-policy ALLOW-CONN”
D. route-policy ALLOW-CONN
if route-type is local and destination in PERMIT_PREFIX then pass
else
drop
end-policy
prefix-set PERMIT_PREFIX
10.10.10.0/24
end-set
router bgp 65000
vrf TEST
rd 65000:10000
address-family ipv4 unicast
redistribute connected route-policy ALLOW-CONN
Answer: A
QUESTION 84
Which three BGP configuration groupings are supported on Cisco IOS XR Software? (Choose three.)
A. peer-group
B. af-group
C. bgp-group
D. session-group
E. neighbor-group
F. as-group
Answer: BDE
Explanation:
Commands relating to a peer group found in Cisco IOS Release 12.2 have been removed from Cisco IOS XR software. Instead, the af-group, session-group, and neighbor-group configuration commands are added to support the neighbor in Cisco IOS XR software:
– The af-group command is used to group address family-specific neighbor commands within an IPv4 or IPv6 address family. Neighbors that have the same address family configuration are able to use the address family group name for their address family- specific configuration. A neighbor inherits the configuration from an address family group by way of the use command. If a neighbor is configured to use an address family group, the neighbor will (by default) inherit the entire configuration from the address family group. However, a neighbor will not inherit all of the configuration from the address family group if items are explicitly configured for the neighbor.
– The session-group command allows you to create a session group from which neighbors can inherit address family-independent configuration. A neighbor inherits the configuration from a session group by way of the use command. If a neighbor is configured to use a session group, the neighbor (by default) inherits the session group’s entire configuration. A neighbor does not inherit all the configuration from a session group if a configuration is done directly on that neighbor.
– The neighbor-group command helps you apply the same configuration to one or more neighbors. Neighbor groups can include session groups and address family groups. This additional flexibility can create a complete configuration for a neighbor. Once a neighbor group is configured, each neighbor can inherit the configuration through the use command. If a neighbor is configured to use a neighbor group, the neighbor (by default) inherits the neighbor group’s entire BGP configuration.
– However, a neighbor will not inherit all of the configuration from the neighbor group if items are explicitly configured for the neighbor. In addition, some part of the neighbor group’s configuration could be hidden if a session group or address family group was also being used.
QUESTION 85
You are implementing OSPF as the IGP using a single OSPF area design. The router memory usage for OSPF is too high. Which two methods can lower the OSPF memory usage? (Choose two.)
A. Enable OSPF synchronization
B. Implement multi-area OSPF
C. Enable OSPF sham links to reduce the number of LSAs
D. Implement route summarization on the ABRs
E. Enable route leaking between Level 1 and Level 2 areas
Answer: BD
QUESTION 86
Why can using the ip tcp path-mtu-discovery command improve BGP convergence?
A. Single packet sizes in TCP sessions are limited.
B. Smaller MSS sizes may reduce BGP convergence times.
C. BGP is allowed to use a larger TCP window size.
D. BGP is enabled to fragment its large update packets.
E. The BGP memory requirements on routers are reduced.
Answer: B
QUESTION 87
What is a key benefit of implementing the bgp dmzlink-bw command?
A. establishes a secure BGP link between eBGP and iBGP peers
B. enables the unequal cost path load balancing feature for external BGP links
C. allows BGP to use link bandwidth as a metric when computing best route selection
D. increases BGP security by dynamically allocating community strings to eBGP routes
Answer: B
QUESTION 88
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 89
How does the extended community cost feature influence the BGP best path selection?
A. alters the BGP AS exit path selection by adding the link cost to the local preference
B. acts as a best path “tie breaker” when multiple IGP equal cost paths occur
C. reflects the bandwidth of links entering the local AS from eBGP neighbors (in the MED attribute)
D. selects the BGP route with the highest attached extended community cost value
E. inserts the cost attribute after the MED attribute comparison, forcing best path route selection if all other preferred route selection criteria are equal
Answer: B
QUESTION 90
What is the maximum number of parallel routes that can be injected into the routing table when using the iBGP multipath load sharing feature?
A. iBGP multipath can support up to 4 parallel paths.
B. iBGP multipath can support up to 6 parallel paths.
C. None, multipath is supported on eBGP only when used in conjunction with the update-source command.
D. The number of parallel paths injected into the routing table will depend on the IGP currently in use within the iBGP domain.
E. The maximum number of parallel paths injected into the routing table is specified by BGP MED and ranges from 2 to 256 parallel paths.
Answer: B
QUESTION 91
What is a key benefit of implementing the bgp dmzlink-bw command?
A. establishes a secure BGP link between eBGP and iBGP peers
B. enables the unequal cost path load balancing feature for external BGP links
C. allows BGP to use link bandwidth as a metric when computing best route selection
D. increases BGP security by dynamically allocating community strings to eBGP routes
Answer: B
QUESTION 92
In a Transit AS, how do the internal routers within the Transit AS forward packets destined for the external networks using a scalable solution?
A. using the default route
B. using the IGP routes where the external networks are redistributed into the IGP by the edge routers
C. using the EBGP routes where the external networks are redistributed into the IBGP by the edge routers
D. using the IBGP routes, then using recursive lookup based on IGP information to resolve the BGP next-hop
Answer: D
QUESTION 93
Which two statements are true about an EBGP session or an IBGP session? (Choose two.)
A. IBGP uses AS-Path to detect routing information loops within the AS.
B. EBGP routes have a default Admin Distance of 20 and IBGP routes have a default Admin Distance of 200.
C. No BGP attributes are changed in EBGP updates except for the next-hop attribute if next-hop-self is configured.
D. Routes learned from an EBGP peer not advertised to another EBGP peer to prevent routing information loops.
E. IBGP uses split horizon to prevent routing information loops; routes learned from an IBGP peer are not advertised to another IBGP peer.
Answer: BE
QUESTION 94
Which AS path access list is used by a multihomed customer to only announce their own address space to their service providers to prevent the multihomed customer from becoming a transit AS?
A. ip as-path access-list permit.*
B. ip as-path access-list permit^$
C. ip as-path access-list permit _$
D. ip as-path access-list permit _^
E. ip as-path access-list permit local-as
ip as-path access-list deny *
F. ip as-path access-list deny.*
ip as-path access-list permit *
Answer: B
QUESTION 95
Refer to the route policies exhibit.
Which five route policies will cause the routes to be dropped or passed? (Choose five)
A. route-policy one will cause the routes to be dropped.
B. route-policy two will cause the routes to be dropped.
C. route-policy three will cause the routes to be dropped.
D. route-policy four will cause the routes to be dropped.
E. route-policy five will cause the routes to be dropped.
F. route-policy one will cause the routes to be passed.
G. route-policy two will cause the routes to be passed.
H. route-policy three will cause the routes to be passed.
I. route-policy four will cause the routes to be passed.
J. route-policy five will cause the routes to be passed.
Answer: ACEGI
QUESTION 96
What are two purposes of the BGP scan-time command? (Choose two.)
A. to tune the BGP process which walks the BGP table and confirms the reachability of next hops
B. to allow faster detection of downed BGP peers
C. to improve BGP convergence time
D. to tune the BGP update interval
E. to decrease the effects of unstable routes by increasing the route suppression time
Answer: AC
Explanation:
http://www.networkers-online.com/blog/2008/12/bgp-performance-tunning-convergence- stability-scalabilityand-nsf-part-2/
Background BGP scanner
It is responsible for BGP housekeeping by scanning both the BGP RIB and the IP RIB and cleaning and sorting things out.
BGP monitors the next hop of the installed routes to verify next-hop reachability and to select, install, and validate the BGP best path. By default, the BGP scanner polls the RIB for this information every 60 seconds.
During the 60 second time period between scan cycles, IGP instabilities or other network failures can cause temporarily black holes and routing loops.
NOTE With Cisco IOS the default timer is 60 seconds for the IPv4 address family and 15 seconds for the VPNv4 address family in order to optimize the VPNs routing table convergence.
This timer can be controlled via the following command:
Router(config-router)#bgp scan-time <5-60>
QUESTION 97
Which two statements about a transit AS are correct? (Choose two.)
A. A transit AS has eBGP connection(s) to only one external AS.
B. Routes between ASs are always exchanged via eBGP.
C. A transit AS uses an IGP like OSPF or ISIS to propagate the external networks within the transit AS.
D. Core routers within a transit AS normally use default routing to reach the external networks.
E. iBGP sessions can be established between non directly connected routers.
Answer: BE
QUESTION 98
Refer to the exhibit. Which configuration is correct for XR4 for an e-BGP session with R1?
A. router bgp 100
neighbor 10.10.14.1
remote-as 100
B. router bgp 100
neighbor 10.10.14.1
remote-as 10
address-family ipv4 unicast
C. router bgp 100
address-family ipv4 unicast
neighbor 10.10.14.1
remote-as 100
address-family ipv4 unicast
D. router bgp 100
address-family ipv4 unicast
neighbor 10.10.14.1
remote-as 100
Answer: C
QUESTION 99
Which two methods implement high availability in OSPF on Cisco IOS XR? (Choose two.)
A. NSF
B. NSR
C. BFD
D. fast hellos
E. sham-links
Answer: AB
QUESTION 100
Drag and Drop Question
Answer:
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