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Q1. Which three potential issues can cause an OSPF adjacency to not come up? (Choose three.)
A. wrong area configured on OSPF peers
B. wrong authentication key configured on OSPF peers
C. different OSPF instance numbers configured on OSPF peers
D. different OSPF instances and VRFs configured with the command: router ospf <number1> vrf <number2>
E. having the no passive-interface statement configured for the interfaces on which OSPF adjacencies are expected to form
F. Layer 2 connectivity problems on the shared medium of the participating OSPF-enabled routers
Answer: A,B,F
Q2. 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
Q3. In Cisco IOS and Cisco IOS XE Software images, when redistributing routes from other routing protocols into OSPF, what is a common reason why some of the routes might not be redistributed into OSPF?
A. The OSPF external metric type (E1 or E2) is not defined.
B. The OSPF seed metric is not defined.
C. The OSPF level (Level 1, Level 2, or Level-1-2) to which the routes will be redistributed into is not defined.
D. The subnets option in the redistribute command is missing.
Answer: D
Q4. Refer to the network diagram in the exhibit.
Assuming the IBGP session within AS 64500 was established using the loopback 0 interface between the two routers, by default, what will be the next hop of the routes from AS 64501 when the routes appear on the router running IBGP only in AS 64500?
A. 192.168.101.11
B. 192.168.101.10
C. 10.1.1.1
D. 10.0.1.1
E. 10.1.10.1
Answer: A
Q5. The S bit in the MPLS header is used for what purpose?
A. To indicate the bottom level in the label stack
B. To indicate if LDP is sync to the IGP
C. To indicate if LDP is sync to the IGP
D. To indicate the status of the LSP
Answer: A
Explanation:
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a 1-bit bottom of stack flag. If this is set, it signifies that the current label is the last in the stack.
Q6. Routes that are received from an IBGP peer will be propagated to which other routers by default?
A. to the EBGP peers only
B. to the IBGP peers only
C. to both EBGP and IBGP peers
D. to no other peers
Answer: A
Q7. Which high-availability routing feature requires the neighbor router to support the graceful restart capability?
A. BFD
B. NSR
C. NSF
D. MTR
Answer: C
Explanation:
On Cisco IOS XR software, NSF minimizes the amount of time a network is unavailable to its users following a route processor (RP) failover. The main objective of NSF is to continue forwarding IP packets and perform a graceful restart following an RP failover.
When a router restarts, all routing peers of that device usually detect that the device went down and then came back up. This transition results in what is called a routing flap, which could spread across multiple routing domains. Routing flaps caused by routing restarts create routing instabilities, which are detrimental to the overall network performance. NSF helps to suppress routing flaps in NSF-aware devices, thus reducing network instability.
NSF allows for the forwarding of data packets to continue along known routes while the routing protocol information is being restored following an RP failover. When the NSF feature is configured, peer networking devices do not experience routing flaps. Data traffic is forwarded through intelligent line cards while the standby RP assumes control from the failed active RP during a failover. The ability of line cards to remain up through a failover
and to be kept current with the Forwarding Information Base (FIB) on the active RP is key
to NSF operation.
When the Cisco IOS XR router running IS-IS routing performs an RP failover, the router
must perform two tasks to resynchronize its link-state database with its IS-IS neighbors.
First, it must relearn the available IS-IS neighbors on the network without causing a reset of
the neighbor relationship. Second, it must reacquire the contents of the link-state database
for the network.
The IS-IS NSF feature offers two options when configuring NSF:
.IETF NSF
.Cisco NSF
If neighbor routers on a network segment are NSF aware, meaning that neighbor routers are running a software version that supports the IETF Internet draft for router restartability, they assist an IETF NSF router that is restarting. With IETF NSF, neighbor routers provide adjacency and link-state information to help rebuild the routing information following a failover. In Cisco IOS XR software, Cisco NSF checkpoints (stores persistently) all the state necessary to recover from a restart without requiring any special cooperation from neighboring routers. The state is recovered from the neighboring routers, but only using the standard features of the IS-IS routing protocol. This capability makes Cisco NSF suitable for use in networks in which other routers have not used the IETF standard implementation of NSF
Q8. When configuring IPv4 and IPv6 IS-IS routing on Cisco IOS XR routers, which three statements are correct? (Choose three.)
A. By default, a single SPF is used for both IPv4 and IPv6, so the IPv4 and IPv6 topology should be the same.
B. By default, the IS-IS router type is Level 1 and Level 2.
C. All IS-IS routers within the same IS-IS area must be configured with the same IS-IS routing process instance ID.
D. By default, metric-style narrow is used.
E. By default, the IS-IS interface circuit type is Level 1 and Level 2.
F. The area IS-IS address-family configuration command is used to specify the IS-IS area address.
Answer: B,D,E
Explanation:
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The default metric style for single topology is narrow metrics. However, you can use either wide metrics or narrow metrics. How to configure them depends upon how single-topology is configured. If both IPv4 and IPv6 are enabled and single-topology is configured, the metric style is configured in the address-family ipv4 stanza. You may configure the metric style in the address-family ipv6 stanza, but it will be ignored in this case. If IPv6 only is enabled and single topology is configured, then the metric style is configured in the address-family ipv6 stanza.
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