1. Which solution supports the use of overlapping addresses on a PE router?
- MPLS
- VRF
- MP-BGP
- IPsec VPNs
Explanation: Topic 15.4.0
In an MPLS L3 VPN architecture, Virtual Routing and Forwarding (VRF) tables allow a Provider Edge (PE) router to maintain multiple independent routing tables. This isolation ensures that different customers can use overlapping or identical private IP address spaces without conflict, as each VRF carries its own unique Routing Information Base (RIB) and Forwarding Information Base (FIB).
2. Which command set would create the type of interface that is required for a spoke router in a spoke-to-spoke DMVPN deployment?
- interface serial 0 and ip unnumbered GigabitEthernet0/0
- interface GigabitEthernet0/0 and ip address dhcp
- interface Tunnel0 and tunnel mode ipsec ipv4
- interface Tunnel0 and tunnel mode gre multipoint
- interface Virtual-Template1 and ip unnumbered Loopback1
- interface Virtual-template1 and ip address dhcp
Explanation: Topic 18.3.0
A spoke-to-spoke DMVPN deployment requires spoke routers to be configured with a multipoint GRE (mGRE) interface. This allows the spokes to dynamically establish direct tunnels with other spokes on demand. The specific command to enable this on a tunnel interface is tunnel mode gre multipoint.
3. What is the function of the RT in MPLS VPNs?
- The RT is used to transform the nonunique IP addresses of the customer into unique VPNv4 addresses.
- The RT attaches a set of VPN identifiers to a route that indicate its membership in several VPNs.
- The RT attaches a set of VPN identifiers to a route that indicate its membership in single VPN.
- The RT attaches a single VPN identifier to a route that indicates its membership in several VPNs.
Explanation: Topic 15.8.0
Route Targets (RTs) are extended BGP community attributes used to identify VPN membership. Unlike Route Distinguishers (RDs), which make a prefix unique, RTs define which VRF tables a route should be imported into or exported from. This mechanism supports complex topologies where a site can be a member of multiple VPNs simultaneously.
4. Which of the following statements is incorrect?
- MPLS labels can correspond to a Layer 3 destination address, QoS, source address, or Layer 2 circuit.
- MPLS does not require a routing table lookup on core routers.
- MPLS works in IP networks only.
- MPLS uses labels to forward packets.
Explanation: Topic 14.3.0
This statement is incorrect because MPLS was specifically designed to be multiprotocol, meaning it can support multiple Layer 3 protocols beyond just IP. It is capable of forwarding non-IP protocols because the labeling technology is applicable to any network layer protocol.
5. Which are two normal functions of an edge LSR? (Choose two.)
- do not impose labels
- pop labels at the egress router
- pop labels at the ingress router
- impose labels at the ingress router
- impose labels at the egress router
Explanation: Topic 14.4.1
Edge LSRs perform different functions based on the direction of traffic flow. An Ingress LSR receives unlabeled packets and imposes (pushes) a label stack before forwarding them into the MPLS domain. Conversely, an Egress LSR receives labeled packets, pops (removes) the labels, and forwards the original IP packet to the destination.
6. Which verification command displays the type of NHRP mapping that a router has established?
- show ip nhrp nhs detail
- show dmvpn detail
- show ip nhrp
- show interface tunnel 12
Explanation: Topic 18.11.0
The show ip nhrp command is used to display the NHRP cache on a device. The output of this command explicitly shows the "Type" of mapping, which identifies whether the mapping is static (configured manually for the hub) or dynamic (learned through the registration process or queries).
7. A VRF table leverages which Cisco forwarding technology?
- CEF
- DMVPN
- EIGRP
- MPLS
Explanation: Topic 15.4.0
A Virtual Routing and Forwarding (VRF) table is built upon several data structures, one of which is a dedicated Cisco Express Forwarding (CEF) table. This table is essentially a per-VRF Forwarding Information Base (FIB) used to make definitive forwarding decisions for packets arriving on interfaces associated with that specific VRF.
8. Which mechanism provides dynamic mutual discovery of spoke devices in DMVPN deployments?
- Expired Certificate List
- GRE
- NHRP
- IKE
- DHCP
Explanation: Topic 18.3.0
Next Hop Resolution Protocol (NHRP) is the mechanism that enables dynamic mutual discovery in DMVPN deployments. Each spoke router registers its public (NBMA) and private (Tunnel) IP addresses with the hub (the NHRP server). When a spoke needs to find another spoke to build a direct tunnel, it queries the NHRP database on the hub to resolve the target's physical address.
9. Which VRF option needs to be enabled to ensure that OSPF are installed into the VRF table when they are redistributed from MP-BGP?
- vrf-lite enable
- no capability vrf-lite
- capability vrf-lite
- no vrf-lite disable
Explanation: Topic 17.8.0
The capability vrf-lite subcommand is required when configuring OSPF as the PE-CE routing protocol. By default, OSPF includes loop prevention mechanisms (like the DN bit) that may prevent it from installing routes learned from MP-BGP into the local VRF table; enabling capability vrf-lite disables these checks, allowing the routes to be correctly processed and installed.
10. Which VPN-aware routing protocol is typically used to carry VPN routes across the MPLS domain?
- EIGRP
- OSPF
- MP-BGP
- IS-IS
Explanation: Topic 15.5.0
MP-BGP is the only routing protocol used to carry customer VPN routes across the MPLS P-network between Provider Edge (PE) routers. It is chosen because it is the only protocol with the necessary scalability to handle the large volume of routes associated with many different customer VPNs.
11. What does an FEC use to forward packets across the MPLS network?
- Egress PE router IP address
- Egress PE router ID
- LSR Next-hop IP address
- LSR Next-hop label
Explanation: Topic 14.10.0
In an MPLS network, while the next-hop IP address is used by the control plane to determine the path, the actual forwarding decisions in the data plane are made using labels. A Forwarding Equivalence Class (FEC) is a group of packets forwarded in the same manner, and once a packet is assigned to a FEC at the ingress, it is represented by a label. Throughout the MPLS domain, each LSR uses the next-hop label (the label value assigned by the downstream/next-hop LSR for that specific FEC) to forward the packet. The sources explicitly state that the next-hop label dictates that the outgoing packet should be labeled and forwarded to the downstream router.
12. Which router in the MPLS L3 VPN network is responsible for applying the RD to and IPv4 prefix?
- P router
- Core router
- CE router
- Backbone router
- PE router
Explanation: Topic 15.7.0
The Provider Edge (PE) router is responsible for customer route propagation across the MPLS VPN network. When the PE router receives an IPv4 routing update from a CE router, it prepends a 64-bit Route Distinguisher (RD) to the prefix to create a globally unique 96-bit VPNv4 address. P routers and CE routers do not participate in this process; P routers are unaware of VPN routes, and CE routers run standard IP software.
13. Which protocol is used to transport VPN labels between PE routers?
- the core IGP
- RSVP
- MP-BGP
- LDP
Explanation: Topic 16.8.0
The egress PE router allocates a VPN label for every route it learns from its connected CE routers. This VPN label is transported from the egress PE to the ingress PE routers using Multiprotocol BGP (MP-BGP). Every MP-BGP update carries the VPNv4/VPNv6 prefix along with the specific label assigned by the egress PE.
14. Which routing protocol does the CE router run?
- any VPN-aware BGP protocol
- any VPN-aware IP routing protocol
- any IP routing protocol
- any VPN-aware link-state protocol
Explanation: Topic 16.2.1
From the perspective of a Customer Edge (CE) router, the MPLS L3 VPN backbone appears as a standard corporate backbone. The CE router is not required to be VPN-aware and does not need any specific configuration to participate in the VPN domain. It simply runs standard IP routing software (such as EIGRP, OSPF, RIPv2, or BGP) to exchange routing information with the PE router.
15. Which type of routers exchange VPNv4 routes?
- P router
- P and PE routers
- PE router
- CE router
Explanation: Topic 16.2.3
In an MPLS L3 VPN architecture, PE routers are the only devices that exchange VPNv4/VPNv6 routes. They do so via MP-IBGP sessions with other PE routers. P routers (provider core routers) do not carry VPN routes and only maintain reachability for the core provider network via an IGP. CE routers only handle standard IPv4/IPv6 prefixes.
16. On which two devices are VRFs usually configured? (Choose two.)
- CE router
- Internal router
- Backbone router
- PE router
- P router
Explanation: Topic 17.5.0
In an MPLS L3 VPN, PE routers use VRFs to maintain separate routing tables for different customers, ensuring traffic isolation. Additionally, with the VRF-Lite feature, CE routers (customer edge devices) can also be configured with VRFs to support multiple routing domains on a single device.
17. Which plane is best described as “a simple label-based forwarding engine”?
- data plane
- ground plane
- routing plane
- control plane
Explanation: Topic 14.5.2
The data plane (or forwarding plane) is described as a simple forwarding engine that operates independently of routing protocols. It forwards packets to the correct interface based on information in the LFIB (for labels) or the FIB (for destination IP addresses).
18. Which two of the following correctly describe the routing tables and their contents that are implemented on the PE router to support an MPLS L3 VPN? (Choose two.)
- Global IP routing table—contains all core IGP routes and the IPv4 routes
- Global IP routing table—contains all core IGP routes and CE routes
- VRFs—contain CE routes and VPNv4 routes
- VRFs—contain IGP routes and VPNv6 routes
- MPLS routing table--contains BGP routes
Explanation: Topic 16.4.0
On a PE router, the global IP routing table contains core routes from the provider's IGP and Internet routes (standard IPv4/IPv6). The VRF tables are populated with intra-VPN routes learned from CE routers and VPNv4/VPNv6 routes received from other PE routers via MP-BGP.
19. Which of the following is not a foundation of traditional IP routing?
- Regardless of protocol, routers always forward packets according to the IP destination address only (except for using PBR).
- Route lookups are performed on every router.
- Routing is performed by assigning a label to an IP destination.
- Routing protocols are used on all devices, to distribute routing information.
Explanation: Topic 14.2.0
Traditional IP routing is based on three foundations: (1) using routing protocols on all devices, (2) forwarding based on destination IP addresses (except for PBR), and (3) performing lookups on every router. Assigning labels to destinations is the fundamental characteristic of MPLS, not traditional IP routing.
20. The architecture of a PE router in an MPLS VPN is similar to which traditional VPN module?
- the dedicated PE router overlay model
- the dedicated CE router overlay model
- the dedicated PE router peer-to-peer model
- the dedicated P router peer-to-peer model
Explanation: Topic 15.2.0
The architecture of an MPLS L3 VPN is based on the peer-to-peer model. Specifically, it is described as being very similar to the dedicated PE router model, where customer traffic is isolated, but instead of using a separate physical router for each customer, a single PE router uses VRFs to provide that same isolation.
21. What is the MPLS L3 VPN core routers called?
- P router
- CE router
- Core router
- PE router
- Backbone router
Explanation: Topic 15.2.0
In the MPLS L3 VPN architecture, P routers are the routers located in the core of the provider's network (P-network). They interface with other provider core routers or Provider Edge (PE) routers and are responsible only for label switching, remaining unaware of specific customer VPN routes.
22. How does a PE router know in which VRF table to install received routes for a customer?
- Customer routes are identified by the RT contained in the extended BGP community.
- Customer routes are identified by the MED.
- Customer routes are identified by the RD contained in the extended BGP community.
- Customer routes are identified by the metric.
Explanation: Topic 15.8.0
Route Targets (RTs) are used as identifiers to indicate VPN membership and are encoded as extended BGP communities. When a PE router receives MP-BGP updates, it uses the attached RTs to decide which routes to import into specific VRF tables based on the import RTs configured for those tables.
23. Which control plane table is built using an LDP?
- RIB
- LIB
- LFIB
- FIB
Explanation: Topic 14.5.1
The Label Information Base (LIB) is the control plane table built by label exchange protocols such as LDP. LDP binds labels to network prefixes learned via routing protocols and stores these bindings in the LIB.
24. The DMVPN hub acts as which type of NHRP device?
- Client
- Filter
- Server
- Reflector
Explanation: Topic 18.5.0
Next Hop Resolution Protocol (NHRP) is a client-server protocol where the hub acts as the NHRP server. The hub maintains a database of mappings between the public (NBMA) IP addresses and the private tunnel IP addresses of all registered spoke routers, which act as NHRP clients.
25. VRF-Lite refers to the deployment of VRFs without the use of which technology?
- MP-BGP
- EIGRP
- OSPF
- MPLS
Explanation: Topic 17.1.0
VRF-Lite is explicitly defined as the deployment of Virtual Routing and Forwarding (VRF) instances on a router without the use of Multiprotocol Label Switching (MPLS). It allows a single device, such as a Customer Edge (CE) router, to support multiple independent routing domains and overlapping IP addresses without requiring an MPLS backbone.
26. An MPLS LSP is usually derived from what provider process?
- DMVPN
- MP-BGP
- LISP
- IGP
Explanation: Topic 14.4.2
An MPLS Label-Switched Path (LSP) represents the contiguous labeled path a packet takes from source to destination. According to the sources, this path is usually derived from IGP routing information (such as OSPF or EIGRP), though it can be configured to diverge from the IGP's preferred path for traffic engineering purposes.
27. Which statement about Cisco IOS DMVPN is not true?
- Enables spoke routers in a spoke-to-spoke design to dynamically locate each other and establish direct tunnels
- Uses a routing protocol to monitor the state of the spoke-to-spoke tunnels
- Uses dynamic routing to populate the routing table of the spoke routers
- Allows IPsec to be automatically triggered to create point-to-point GRE tunnels without any IPsec peering configuration
- Reduces the configuration of the hub router in hub-to-spoke and spoke-to-spoke designs
Explanation: Topic 18.3.0
This statement is not true. The sources explicitly state that while dynamic routing protocols are used to advertise networks and establish adjacencies across permanent hub-and-spoke links, a routing protocol does not monitor the state of spoke-to-spoke tunnels. Instead, the routing logic for these on-demand tunnels is handled by NHRP.
28. Which two statements correctly describe LSRs? (Choose two.)
- An edge LSR is a device that inserts or removes labels on packets and that forwards packets according to labels.
- An LSR is a device that primarily labels packets or removes labels.
- An LSR is a device that forwards packets, according to labels.
- An end LSR is a device that primarily inserts labels on packets or removes labels.
- MPLS does not require LSRs.
Explanation: Topic 14.4.1
An LSR (Label Switch Router) is defined as a router that supports MPLS, understands labels, and forwards packets based on them. An Edge LSR sits at the boundary of the MPLS domain and is specifically responsible for imposing (inserting) labels on incoming unlabeled packets or disposition (removing) labels from packets leaving the domain.
29. How can P routers forward VPN packets if they do not have VPN routes?
- They forward based on the MP-BGP next hop.
- They forward based on the VPN label.
- They forward based on a routing table lookup of the IP address.
- They forward based on the LSP label.
Explanation: Topic 16.6.0
In an MPLS L3 VPN, packets are sent across the provider core using a two-level label stack. The P routers (core routers) only examine the top label, which is the LDP-assigned label for the egress PE router. This label defines the LSP (Label Switched Path), allowing core routers to switch the packet toward the destination PE without needing any knowledge of the inner VPN routes.
30. Which step in the DMVPN spoke configuration sequence is optional because default settings can be used?
- configuring NHRP client parameters
- configuring a transform set
- creating an mGRE tunnel interface
- configuring an IPsec profile
- generating or configuring authentication credentials to authenticate the hub and other spoke devices
Explanation: Topic 18.9.0
During the configuration of a DMVPN spoke (or hub), the sources state that configuring a transform set within the IPsec profile is optional. If a specific transform set is not defined, the router will automatically use default IPsec transform sets. Conversely, the IPsec profile itself is mandatory.
31. How has the introduction of complex VPN topologies redefined the meaning of a VPN?
- A site can be part of two VPNs only.
- Two customers can connect in a single VPN.
- A site can be part of one VPN only.
- A site can be part of more than one VPN.
Explanation: Topic 15.8.0
In the MPLS L3 VPN architecture, Route Targets (RTs) were introduced specifically to support complex topologies. While a Route Distinguisher (RD) makes a prefix unique within a single VRF, RTs are extended BGP communities that identify VPN membership, allowing a single site to be a member of multiple VPNs simultaneously.
32. Which two statements correctly describe MPLS? (Choose two.)
- Traffic can be forwarded according to parameters such as QoS and source address.
- Traditional IP routing would force all traffic to use the same path, according to destination.
- Traditional IP routing does not support traffic engineering.
- MPLS does not support traffic engineering.
Explanation: Topic 14.3.0
MPLS is a flexible forwarding technology where labels can correspond to various parameters beyond just destination networks, such as QoS or source addresses. In contrast, traditional IP routing is structurally bound to destination-address-based lookups, which typically forces all traffic for a specific prefix to follow the same shortest path determined by the IGP.
33. For which two reasons does the label stack contain two labels when supporting MPLS VPNs? (Choose two.)
- The first label indicates the LSP that will be used to reach the egress router.
- The first label indicates the VPN that the packet belongs to.
- The second label indicates the VPN that the packet belongs to.
- The second label indicates the LSP that will be used to reach the egress router.
- The first label indicates which VRF to use
Explanation: Topic 16.6.0
MPLS L3 VPNs use a two-level label stack to forward packets across the provider core. The first (top) label is assigned by LDP and defines the Label-Switched Path (LSP) used to reach the egress PE router. The second (bottom) label is advertised via MP-BGP and identifies the specific VPN or VRF the packet belongs to, telling the egress PE how to forward the packet toward the correct customer site.
34. Which of the following is responsible for the Label Distribution Protocol?
- system plane
- data plane
- forwarding plane
- control plane
Explanation: Topic 14.5.1
The control plane is responsible for Layer 3 protocol exchanges and the building of routing and forwarding tables. Protocols that facilitate label distribution, such as LDP, BGP (for VPN labels), and RSVP (for Traffic Engineering), operate within the control plane to bind labels to network prefixes and populate the Label Information Base (LIB).
35. Which of the following is not part of a VPNv4 prefix?
- Next-hop IP address
- IPv4 address
- VPN label
- RD
- RT
Explanation: Topic 15.6.0
A VPNv4 prefix is a unique 96-bit address used in MPLS L3 VPNs to ensure customer routes remain unique across the service provider's backbone.
According to the sources, here is the breakdown of why the Next-hop IP address is not part of that prefix:
- Composition of a VPNv4 Prefix: It is strictly composed of two parts: a 64-bit Route Distinguisher (RD) and a 32-bit customer IPv4 address. These two elements combined form the 96-bit prefix.
- Attributes vs. Prefixes: While the Route Target (RT), VPN label, and Next-hop IP address are all essential components of an MP-BGP update, they are carried as separate attributes or fields alongside the prefix.
- The Next-Hop specifically: In an MP-BGP update, the Next-hop IP address is a standard BGP attribute used to identify the protocol next-hop (usually the egress PE router's loopback). Structurally, it is a completely separate field from the 96-bit VPNv4 network layer reachability information (NLRI).
In summary, the RD and IPv4 address are the literal pieces of the VPNv4 prefix, whereas the Next-hop IP address is a separate routing attribute.
36. LDP hellos use which UDP port and multicast address? (Choose two.)
- 224.0.0.5
- 464
- 500
- 224.0.0.2
- 646
- 224.0.0.6
Explanation: Topic 14.12.0
LDP uses two steps to establish sessions. First, it sends Hello messages as UDP packets to the "all routers on this subnet" multicast address 224.0.0.2. Both the UDP discovery phase and the subsequent TCP session establishment use the well-known LDP port number 646.
37. Which protocol is used to transport customer routes directly between PE routers?
- OSPF
- MP-BGP
- VPN
- RIP
Explanation: Topic 15.5.0
To maintain scalability in an MPLS L3 VPN environment, MP-BGP is the only protocol used to transport customer routes directly between PE routers. It is capable of carrying the large volume of routes required for multiple customer VPNs while keeping individual customer address spaces independent.
38. Which routers are MPLS VPNs aware of?
- P routers
- all provider routers
- CE routers
- PE routers
Explanation: Topic 16.2.3
In the MPLS L3 VPN architecture, PE routers are the only routers that see all routing aspects of the VPN. They exchange VPN routes with CE routers, maintain separate VRF tables for customer isolation, and exchange VPNv4/VPNv6 routes with other PE routers via MP-BGP. In contrast, P routers remain unaware of VPN routes and only perform label switching based on core reachability.
39. Which step in the DMVPN hub configuration sequence is optional?
- creating an mGRE tunnel interface
- configuring an IPsec profile
- configuring an IKE policy
- generating or configuring authentication credentials to authenticate spoke devices
Explanation: Topic 18.8.0
In the DMVPN hub configuration sequence, configuring a specific IKE policy is optional; if one is not defined, the hub will simply use default IKE policies to interface with peers. Other steps, such as configuring an IPsec profile, are mandatory even if the profile is empty.
40. What is the length of the label field in the MPLS header?
- 20 bits
- 32 bits
- 16 bits
- 64 bits
Explanation: Topic 14.11.0
While the total MPLS header (or shim header) is 32 bits long, the specific label value field within that header is 20 bits. This 20-bit value is the number assigned by the router to identify a specific prefix or Forwarding Equivalence Class (FEC).
41. Labels that are associated with the next-hop router are inserted into which data plane table?
- LIB
- RIB
- LFIB
- FIB
Explanation: Topic 14.14.2
While a router maintains all labels received from its LDP peers in the LIB (Label Information Base), only the specific labels received from the next-hop router for a destination prefix are installed into the LFIB (Label Forwarding Information Base). The LFIB is the data plane table used for actual label-switching operations.
42. Which router assigns the VPN label?
- egress CE
- P router
- ingress PE
- egress PE
- ingress CE
Explanation: Topic 16.8.0
In an MPLS L3 VPN, the egress PE router is responsible for allocating a VPN label for every route it learns from its connected CE routers. This label is then advertised to the ingress PE router via MP-BGP so the ingress PE knows how to identify that specific VPN's traffic upon arrival at the egress point.
43. Which protocol is used to encrypt and authenticate the data that is sent across a DMVPN tunnel?
- IPsec
- NHRP
- GRE
- mGRE
Explanation: Topic 18.3.0
IPsec is the component of DMVPN that provides cryptographic transmission protection for data. While GRE and mGRE provide the tunneling and encapsulation for multiprotocol and multicast traffic, they offer no built-in security; therefore, they must be combined with IPsec to ensure data is encrypted and authenticated.
44. Which BGP function do MPLS L3 VPNs use to transport RTs?
- standard communities
- metric
- extended communities
- MED
Explanation: Topic 15.8.0
Route Targets (RTs) are implemented as extended BGP communities. These 64-bit attributes are attached to VPNv4/VPNv6 routes to indicate VPN membership, allowing receiving PE routers to decide which routes should be imported into their local VRFs.
45. What is the function of the RD in an MPLS VPN?
- The RD is used to transform the unique IP addresses of the customer into nonunique IPv4 addresses.
- The RD is used to transform the unique IP addresses of the customer into nonunique VPNv4 addresses.
- The RD is used to transform the nonunique IP addresses of the customer into unique VPNv4 addresses.
- The RD is used to transform the nonunique IP addresses of the customer into unique IPv4 addresses.
Explanation: Topic 15.5.0
The Route Distinguisher (RD) is a 64-bit value prepended to a customer's nonunique 32-bit IPv4 address. This process creates a 96-bit globally unique VPNv4 address, which allows BGP to distinguish between and transport overlapping address spaces from different customers across the provider's shared backbone.
46. Which protocol would a PE router use to support an existing Internet routing scheme?
- BGP VPNv4
- IS-IS
- BGP IPv4
- EIGRP
Explanation: Topic 16.3.0
While PE routers use MP-BGP (VPNv4/VPNv6) for internal customer VPN routes, they must also support traditional Internet connectivity. The sources state that PE routers can run standard IPv4 BGP in the global routing table to exchange Internet routes with other PE routers, ensuring support for existing Internet routing schemes.
47. Which three options are features of GRE? (Choose three.)
- multicast support
- Dynamic MPLS configuration
- low CPU usage
- can be used with IPsec VPNs
- QoS capabilities
- provides cryptographic traffic protection
Explanation: Topic 18.4.0
GRE is a versatile protocol that supports IP multicast and non-IP protocols, allowing for the use of dynamic routing protocols across tunnels. It is frequently combined with IPsec because GRE alone provides no cryptographic protection,. Additionally, because GRE tunnels use standard Cisco IOS interfaces, they can offer finer-grained QoS features compared to other tunneling methods.
48. What can happen if two different sites with different access and security requirements are associated with the same virtual routing table?
- This scenario is not possible.
- Some of the sites might be able to access destinations that they should not be able to access.
- Sites are in different VRFs.
- Sites are in different VPNs.
Explanation: Topic 17.4.0
A VRF is defined as a routing and forwarding instance meant for sites that share the same connectivity requirements. Because all interfaces assigned to a single VRF share the same routing table (RIB) and forwarding table (FIB), failing to isolate sites with different security or access needs into separate VRFs would allow them to see and reach each other's internal networks.
49. What is the size of an MPLS label?
- 8 bytes
- 4 bytes
- 2 bytes
- 6 bytes
Explanation: Topic 14.9.0
The sources explicitly define an MPLS label as a short, 4-byte (32-bit), fixed-length identifier. Within this 4-byte header, 20 bits are used for the actual label value, while the remaining bits are used for the experimental field (QoS), bottom-of-stack indicator, and TTL.
50. Which command can be used with the Cisco IOS VRF migration tool to ensure that all route-target policies are copied to their respective address families?
- vrf upgrade-cli multi-af-mode common-policies
- vrf upgrade-cli multi-af-mode non-common-policies
- vrf upgrade-cli multi-af-mode vrf
- vrf upgrade-cli multi-af-mode policy vrf
Explanation: Topic 17.7.0
When migrating from the legacy single-protocol VRF configuration (ip vrf) to the modern multiprotocol VRF configuration (vrf definition), the Cisco IOS migration tool provides options for how existing route-target policies are handled:
- common-policies: Copies the route-target policies to the global/common part of the new VRF configuration. This ensures that the import and export policies apply automatically across all configured address families (such as IPv4 and IPv6) within that VRF.
- non-common-policies: Keeps the route-target policies restricted to the IPv4 address family sub-mode only, preventing them from automatically applying to other address families.
