View Full Cisco CCNP Service Provider 300-510 Exam Dumps and Practice Test Dumps

 

Question 101. An IS-IS Level-2 router has recently lost connectivity to several destinations, and its LSP indicates the overload bit is set. What is the expected effect on transit traffic?

1. The router becomes the preferred exit for external routes
2. All IS-IS adjacencies are immediately terminated
3. Other routers avoid selecting the overloaded router as a transit path
4. The router stops advertising all directly connected prefixes

Correct Answer: 3. Other routers avoid selecting the overloaded router as a transit path

Explanation :-

The IS-IS overload bit tells other routers that the advertising router should not normally be used as a transit router. This is useful during startup, synchronization, or situations where the router’s routing database or forwarding resources are not ready to carry transit traffic. The router can still advertise reachability to destinations directly connected to it, allowing traffic destined specifically for those networks to reach the device. Setting the overload bit does not inherently terminate IS-IS adjacencies or suppress every local prefix. Engineers should therefore consider the overload state when a router unexpectedly disappears from preferred transit paths.

Question 102. Two OSPF routers on a point-to-point link have successfully discovered each other, but their adjacency remains in the INIT state. Which issue should be investigated first?

1. Whether the router is receiving the neighbor’s Hello packets with its own Router ID listed
2. Whether the OSPF DR has been elected
3. Whether BGP Local Preference is configured
4. Whether an MPLS VPN label exists

Correct Answer: 1. Whether the router is receiving the neighbor’s Hello packets with its own Router ID listed

Explanation :-

The OSPF INIT state indicates that a router has received a Hello packet from its neighbor but has not yet seen its own Router ID in the neighbor’s Hello neighbor list. This usually indicates a problem with bidirectional Hello communication or an issue preventing the neighbor from recognizing the local router. On a point-to-point network, DR and BDR election is not the primary concern. BGP Local Preference and MPLS VPN labels are unrelated to OSPF adjacency establishment. Troubleshooting should therefore begin by verifying bidirectional OSPF Hello exchange, interface configuration, network type, authentication, and any filtering that could interfere with OSPF packets.

Question 103. A provider wants to prevent a BGP route learned from one external autonomous system from being advertised to another external autonomous system while still permitting internal propagation. Which well-known community can be used?

1. INTERNET
2. NO_ADVERTISE
3. LOCAL_PREF
4. NO_EXPORT

Correct Answer: 4. NO_EXPORT

Explanation :-

The NO_EXPORT well-known BGP community is used to prevent a route from being advertised outside the local autonomous system, while the route can still be propagated internally according to normal BGP rules. This makes it useful when a provider wants a route to remain within its own AS rather than being propagated to external peers or transit providers. NO_ADVERTISE is more restrictive because it prevents the route from being advertised to any BGP peer. INTERNET does not impose this restriction, and LOCAL_PREF is a path-selection attribute rather than a route-propagation community. Correct community selection is important for controlling BGP route scope.

Question 104. A Cisco router receives two otherwise identical BGP routes. One route has a higher LOCAL_PREF than the other. Which path is normally preferred?

1. The route with the longer AS_PATH
2. The route with the higher LOCAL_PREF
3. The route with the higher MED
4. The route with the lower Weight

Correct Answer: 2. The route with the higher LOCAL_PREF

Explanation :-

LOCAL_PREF is a major BGP path-selection attribute used to influence the preferred exit path from an autonomous system. When comparing otherwise eligible routes, the higher Local Preference is normally preferred. This allows an organization to consistently direct outbound traffic through a desired external connection across its internal BGP topology. AS_PATH length is considered later in the best-path process, and MED has a different purpose and comparison scope. Weight is Cisco-specific and is locally significant, with a higher value normally preferred. Therefore, when Local Preference differs and applicable earlier criteria are equal, the higher value is normally selected.

Question 105. Which IS-IS PDU provides a complete summary of the LSP database on a broadcast network?

1. CSNP
2. PSNP
3. Hello PDU
4. BGP UPDATE

Correct Answer: 1. CSNP

Explanation :-

A Complete Sequence Number PDU (CSNP) provides a summary of the LSPs known by an IS-IS router. On broadcast networks, the DIS periodically transmits CSNP information to help routers compare their local link-state databases with the database summary. If a router identifies missing or outdated LSP information, PSNPs can be used to request specific LSPs or acknowledge information. Hello PDUs establish and maintain IS-IS adjacencies, while BGP UPDATE messages belong to BGP. CSNPs are therefore central to IS-IS database synchronization and consistency on broadcast segments.

Question 106. A service provider has an MPLS LDP session that remains down even though both routers can ping each other’s loopback addresses. Which additional factor should be checked when the LDP transport connection is expected to use the loopbacks?

1. BGP MED
2. PIM Rendezvous Point
3. LDP router ID and TCP connectivity
4. OSPF DR priority

Correct Answer: 3. LDP router ID and TCP connectivity

Explanation :-

LDP uses discovery mechanisms and TCP for reliable session establishment. When loopback addresses are used for the LDP session, the routers must have appropriate reachability to those addresses and the expected LDP router IDs must be selected correctly. Engineers should verify the LDP router ID, TCP connectivity, source addressing, and any filtering that could block the session. Successful ICMP ping alone does not guarantee that the required TCP session can form. BGP MED, PIM RP selection, and OSPF DR priority do not directly establish an LDP session. These checks are especially important in service-provider MPLS troubleshooting.

Question 107. A network engineer wants to make an iBGP-learned route visible to other iBGP routers without requiring a full-mesh of iBGP sessions. Which feature is designed for this purpose?

1. BGP dampening
2. Route reflection
3. MED
4. AS_PATH prepending

Correct Answer: 2. Route reflection

Explanation :-

Traditional iBGP requires a full mesh because an iBGP speaker does not normally advertise an iBGP-learned route to another iBGP peer. Route reflection addresses this scalability limitation by allowing designated route reflectors to reflect eligible routes between clients and other BGP speakers. This reduces the number of required iBGP sessions while preserving route distribution across the autonomous system. BGP dampening manages unstable routes, MED influences path selection, and AS_PATH prepending manipulates the apparent AS-path length for traffic engineering. Route reflection is therefore the mechanism intended to solve the iBGP full-mesh scalability problem.

Question 108. An MPLS L3VPN packet enters a PE router from a customer interface. Which label is primarily used to identify the VPN service or VRF at the remote PE?

1. OSPF Router ID
2. BGP MED
3. IGP metric
4. VPN label

Correct Answer: 4. VPN label

Explanation :-

In an MPLS L3VPN, the VPN or service label identifies the VPN route or forwarding context at the egress PE. A typical packet may carry an outer transport label to reach the remote PE and an inner VPN label that tells the egress PE which VRF or service context should process the packet. The transport label is handled by the MPLS core, while the VPN label is associated with the service-specific forwarding decision. OSPF Router IDs, BGP MED, and IGP metrics do not identify the customer’s VPN forwarding context. Understanding the label stack is essential for MPLS L3VPN troubleshooting.

Question 109. Which BGP attribute is commonly manipulated by adding repeated copies of the local AS number to influence inbound traffic engineering?

1. Weight
2. LOCAL_PREF
3. AS_PATH
4. NEXT_HOP

Correct Answer: 3. AS_PATH

Explanation :-

AS_PATH prepending modifies the AS_PATH attribute by adding additional occurrences of the originating autonomous system number. This makes a particular route advertisement appear to have a longer AS_PATH to neighboring networks. Because AS_PATH length can influence BGP path selection, prepending may cause other networks to prefer an alternative advertisement. The technique is primarily useful for influencing inbound traffic, although its actual effect depends on the policies and other BGP attributes used by neighboring autonomous systems. Weight and LOCAL_PREF influence local or internal path selection, while NEXT_HOP identifies the forwarding next hop.

Question 110. In an OSPF NSSA, an external route is redistributed by an ASBR. Which LSA type is used to represent that route within the NSSA before possible translation by an ABR?

1. Type 7
2. Type 3
3. Type 4
4. Type 1

Correct Answer: 1. Type 7

Explanation :-

OSPF NSSAs permit external route redistribution while preventing ordinary Type 5 LSAs from entering the area. An ASBR inside an NSSA therefore originates Type 7 LSAs for redistributed external routes. An NSSA ABR can translate eligible Type 7 LSAs into Type 5 LSAs when advertising those external routes into the wider OSPF domain. Type 3 LSAs represent inter-area networks, Type 4 LSAs provide reachability information for ASBRs, and Type 1 LSAs describe routers and their links. Type 7 behavior is therefore a key consideration when troubleshooting external route redistribution within an NSSA.

Question 111. A provider wants a BGP route to remain available inside its autonomous system but not be advertised to external BGP neighbors. Which community is appropriate?

1. NO_ADVERTISE
2. NO_EXPORT
3. INTERNET
4. ACCEPT_OWN

Correct Answer: 2. NO_EXPORT

Explanation :-

NO_EXPORT is designed to prevent a BGP route from being advertised outside the local autonomous system, while allowing internal propagation according to BGP rules. This can be useful when a provider needs multiple internal routers to know about a route but does not want that route to leave the autonomous system. NO_ADVERTISE imposes a stronger restriction by preventing advertisement to any BGP peer. INTERNET generally indicates normal advertisement, while ACCEPT_OWN has a specialized function associated with particular BGP VPN policy scenarios. The distinction between these communities is important when implementing route-propagation policies.

Question 112. A Segment Routing policy needs to force traffic over a specific link between two directly connected routers rather than simply forwarding toward the destination node. Which SID provides this capability?

1. Node SID
2. Binding SID
3. Anycast SID
4. Adjacency SID

Correct Answer: 4. Adjacency SID

Explanation :-

An Adjacency SID represents a specific adjacency from a Segment Routing node toward a directly connected neighbor. Including an Adjacency SID in an SR policy segment list can force traffic to traverse that particular link. A Node SID generally represents shortest-path forwarding toward a node, so it does not necessarily force use of one particular adjacency. A Binding SID identifies an SR policy or segment-list behavior, while an Anycast SID can represent a set of nodes sharing an anycast function. Adjacency SIDs are therefore useful when precise link-level path control is required.

Question 113. Which mechanism can provide rapid local repair in a Segment Routing network after a link or node failure?

1. Route Target import
2. BGP Weight
3. TI-LFA
4. OSPF Type 3 LSA

Correct Answer: 3. TI-LFA

Explanation :-

Topology Independent Loop-Free Alternate (TI-LFA) provides local protection for Segment Routing networks. Backup repair paths can be computed before a failure occurs, allowing the router adjacent to the failure to redirect traffic rapidly. This reduces dependence on waiting for complete IGP convergence before forwarding can recover. TI-LFA can protect against different failure scenarios, including link and node failures, depending on the topology and configured protection requirements. Route Targets control VPN route import, BGP Weight affects local BGP selection, and OSPF Type 3 LSAs provide inter-area reachability. TI-LFA directly addresses fast local restoration.

Question 114. A BGP administrator wants to ensure that a customer route is not accepted unless it matches an explicitly permitted prefix. Which combination provides precise prefix-based inbound filtering?

1. MED and BFD
2. Route Target and RD
3. Prefix list and routing policy
4. PIM and IGMP

Correct Answer: 3. Prefix list and routing policy

Explanation :-

A prefix list combined with a routing policy provides precise control over which prefixes are accepted from a BGP neighbor. The prefix list can identify permitted or denied network ranges, while the policy applies the filtering decision to the appropriate BGP direction. This is particularly important for customer sessions, where providers typically need to accept only authorized prefixes. Route Targets and Route Distinguishers are associated with MPLS VPNs, BFD detects failures, and PIM/IGMP handle multicast. Prefix-based filtering should be applied carefully, often with an explicit deny-all condition after the required permitted prefixes.

Question 115. Which BGP feature is specifically intended to protect a router from receiving an unexpectedly large number of routes from a neighbor?

1. Route reflection
2. Add-Path
3. ORF
4. Maximum-prefix

Correct Answer: 4. Maximum-prefix

Explanation :-

The BGP maximum-prefix feature establishes a limit on the number of prefixes that a router will accept from a particular BGP neighbor. This provides an operational safeguard against events such as accidental route leaks or unexpectedly large advertisements. Administrators can configure warning thresholds and actions when the configured maximum is approached or exceeded. Route reflection addresses iBGP scalability, Add-Path provides multiple path advertisements, and ORF allows filtering information to be communicated between BGP peers. Maximum-prefix is therefore the feature directly designed to limit the number of received BGP routes.

Question 116. A router is configured as an OSPF ABR. Which LSA type does it normally generate to advertise an internal network from one area into another area?

1. Type 1
2. Type 3
3. Type 5
4. Type 7

Correct Answer: 2. Type 3

Explanation :-

An OSPF Area Border Router generates Type 3 Summary LSAs to advertise networks from one OSPF area into another. These LSAs allow routers in the receiving area to learn inter-area reachability without having to maintain the detailed topology database of the originating area. Type 1 LSAs describe routers and their links within an area. Type 5 LSAs advertise external routes, while Type 7 LSAs are used for external routes inside an NSSA. When investigating missing inter-area routes, administrators should examine the ABR, Type 3 LSAs, area-range configuration, and any route-filtering policies.

Question 117. A multicast receiver joins group 232.1.1.1, and the network is designed to use Source-Specific Multicast. Which protocol behavior allows the receiver to identify the desired source rather than relying on a shared Rendezvous Point?

1. PIM Assert
2. PIM BSR
3. IGMPv3 source-specific membership
4. MSDP peer discovery

Correct Answer: 3. IGMPv3 source-specific membership

Explanation :-

Source-Specific Multicast (SSM) uses a receiver’s explicit interest in both a multicast source and multicast group. IGMPv3 supports source-specific membership reports, allowing a receiver to indicate which source it wants for a particular multicast group. This differs from traditional PIM-SM shared-tree operation, where a Rendezvous Point can initially play a central role in establishing multicast distribution. PIM Assert resolves forwarding conflicts on shared networks, BSR distributes RP information, and MSDP exchanges active-source information between multicast domains. IGMPv3 source filtering is therefore fundamental to SSM operation.

Question 118. Which BGP attribute identifies the IP address that should be used as the next hop toward a BGP route?

1. NEXT_HOP
2. ORIGIN
3. LOCAL_PREF
4. COMMUNITY

Correct Answer: 1. NEXT_HOP

Explanation :-

The BGP NEXT_HOP attribute identifies the IP address that a router should use as the next-hop destination when forwarding traffic toward the advertised prefix. The BGP route can be selected successfully only if the next-hop address is reachable through the local routing table. In service-provider networks, next-hop behavior is particularly important when routes are exchanged between PE routers, route reflectors, and external peers. ORIGIN identifies how a route was introduced into BGP, LOCAL_PREF influences path selection, and COMMUNITY carries policy information. NEXT_HOP therefore directly connects BGP route information with forwarding reachability.

Question 119. An MPLS network uses LDP to distribute labels based on the IGP’s shortest-path routing information. Which statement correctly describes the relationship between the IGP and LDP?

1. LDP independently calculates the complete IP topology
2. LDP replaces the IGP for IP reachability
3. LDP selects BGP best paths
4. The IGP provides reachability while LDP distributes labels for applicable FECs

Correct Answer: 4. The IGP provides reachability while LDP distributes labels for applicable FECs

Explanation :-

LDP generally works alongside an IGP rather than replacing it. The IGP establishes IP reachability and calculates paths through the provider network, while LDP distributes labels associated with Forwarding Equivalence Classes. These labels allow packets to be forwarded using MPLS label switching along paths consistent with the underlying routing information. LDP does not independently replace the IGP’s topology calculation or perform BGP best-path selection. Understanding this relationship helps troubleshoot MPLS problems where IP routing may be correct but label distribution or forwarding state is incomplete.

Question 120. A route reflector receives a route from one client and needs to advertise that route to another route-reflector client. Which BGP rule is the route reflector specifically designed to overcome?

1. eBGP routes cannot contain an AS_PATH
2. iBGP-learned routes are normally not advertised to other iBGP peers
3. BGP cannot advertise routes with communities
4. MPLS labels cannot be exchanged through BGP

Correct Answer: 2. iBGP-learned routes are normally not advertised to other iBGP peers

Explanation :-

The traditional iBGP split-horizon rule prevents a router from advertising an iBGP-learned route to another iBGP peer. Without an alternative mechanism, every iBGP router would need a full-mesh of sessions to ensure complete route visibility. Route reflection modifies this behavior by allowing designated route reflectors to reflect eligible routes between clients and other BGP speakers. This significantly reduces the number of required iBGP sessions in large service-provider networks. Route reflection uses attributes such as ORIGINATOR_ID and CLUSTER_LIST to help prevent routing loops while maintaining scalable route distribution.