L3 VPN( Single Homed, Multihomed, Static Routing, RIP, OSPF, Bgp, Vrrp)
By IMS Asia (https://www. Imsasia. Com)
Questions and Answers
- 1.
In a Layer 3 VPN, what are the roles of the CE router? (choose two)
- A.
Assign an MPLS label for the routes.
- B.
Forward traffic using MPLS labels.
- C.
Advertise routes from a site to the provider network.
- D.
Receive routes from the provider network about remote sites.
Correct Answer(s)
C. Advertise routes from a site to the provider network.
D. Receive routes from the provider network about remote sites.Explanation
The CE router in a Layer 3 VPN has two roles: advertising routes from a site to the provider network and receiving routes from the provider network about remote sites. This means that the CE router is responsible for exchanging routing information with the provider network and ensuring that the correct routes are advertised and received for communication between the site and remote sites.Rate this question:
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- 2.
In a Layer 3 VPN environment using RSVP for MPLS reachability, how many labels are placed on a data packet by the ingress PE router?
- A.
1
- B.
2
- C.
3
- D.
4
Correct Answer
B. 2Explanation
In a Layer 3 VPN environment using RSVP for MPLS reachability, the ingress PE router places two labels on a data packet. The first label is the VPN label, which is used to identify the VPN to which the packet belongs. The second label is the MPLS label, which is used for forwarding the packet within the MPLS network. These two labels are added by the ingress PE router to ensure proper routing and delivery of the packet to the correct destination within the Layer 3 VPN environment.Rate this question:
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- 3.
What routing protocol is not supported between the a PE router and CE router?
- A.
OSPF
- B.
BGP
- C.
IS-IS
- D.
RIP
Correct Answer
C. IS-ISExplanation
IS-IS is not supported between a PE router and CE router. IS-IS (Intermediate System to Intermediate System) is a link-state routing protocol commonly used in large service provider networks. However, it is typically used within the service provider network and not between the provider edge (PE) router and customer edge (CE) router. Instead, protocols like OSPF (Open Shortest Path First), BGP (Border Gateway Protocol), or RIP (Routing Information Protocol) are commonly used between PE and CE routers for exchanging routing information.Rate this question:
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- 4.
PE1 has connections to VPN sites that are served by three remote PE routers. How many LSPs must be established to support rfc 4364?
- A.
An LSP for each local CE device
- B.
An LSP for each remote PE device
- C.
An LSP for each remote CE device
- D.
An LSP for each CE facing interface
Correct Answer
B. An LSP for each remote PE deviceExplanation
In order to support rfc 4364, which is a VPN technology, an LSP (Label Switched Path) needs to be established for each remote PE (Provider Edge) device. This is because the remote PE devices are the ones serving the VPN sites, and each device needs to have its own LSP to ensure proper connectivity and routing within the VPN network. Therefore, the correct answer is that an LSP must be established for each remote PE device.Rate this question:
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- 5.
Which condition must be met to allow a PE router to forward VPN traffic across a LSP in a layer 3 VPN environment?
- A.
The BGP next hop must be in inet.1
- B.
The BGP next hop must be in inet.3
- C.
Must have a bidrectional LSP configured
- D.
Must have a static route configured to allow an RP for connected interfaces
Correct Answer
B. The BGP next hop must be in inet.3Explanation
To allow a PE router to forward VPN traffic across a LSP in a layer 3 VPN environment, the BGP next hop must be in inet.3. This is because inet.3 is the routing table that contains the VPN routes. By having the BGP next hop in inet.3, the PE router can properly route the VPN traffic across the LSP to its destination.Rate this question:
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- 6.
In a Layer 3 VPN, what are the roles of the PE router? (choose two)
- A.
Maintain VPN specfic forwarding tables
- B.
Perform label switching
- C.
Forward VPN data transparently over established LSPs
- D.
Exchange VPN routing information with other PE routers
Correct Answer(s)
A. Maintain VPN specfic forwarding tables
D. Exchange VPN routing information with other PE routersExplanation
The PE router in a Layer 3 VPN has two main roles. Firstly, it maintains VPN-specific forwarding tables, which are used to determine the correct path for forwarding VPN data within the VPN network. Secondly, the PE router exchanges VPN routing information with other PE routers in order to establish and maintain the correct routing paths between different VPN sites. This allows for seamless communication between different sites within the VPN network.Rate this question:
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- 7.
What routes are housed in a VRF table? (choose two)
- A.
Backbone OSPF routes
- B.
L3VPN domain routes
- C.
Routes received from directly connected CE sites
- D.
Routes received from other PE routers with acceptable MP-BGP attributes
Correct Answer(s)
C. Routes received from directly connected CE sites
D. Routes received from other PE routers with acceptable MP-BGP attributesExplanation
The routes housed in a VRF table are the routes received from directly connected CE sites and the routes received from other PE routers with acceptable MP-BGP attributes. These routes are stored in the VRF table to ensure proper routing and forwarding within the Virtual Routing and Forwarding (VRF) instance. The VRF table allows for the separation and isolation of different routing domains or VPNs within a single network infrastructure. By storing these routes in the VRF table, the network can accurately determine the next hop for each packet based on the VRF instance it belongs to.Rate this question:
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- 8.
What is the correct order for the fields in a VPN-IPv4 NLRI?
- A.
Mask, Route Distinguisher, MPLS Label, IP Prefix
- B.
Mask, MPLS Label, Route Distinguisher, IP Prefix
- C.
MPLS Label, Route Distinguisher, Mask, IP Prefix
- D.
Route Distinguisher, MPLS Label, Mask, IP Prefix
Correct Answer
B. Mask, MPLS Label, Route Distinguisher, IP PrefixExplanation
The correct order for the fields in a VPN-IPv4 NLRI is Mask, MPLS Label, Route Distinguisher, IP Prefix. In a VPN-IPv4 NLRI, the mask field specifies the length of the IP prefix, the MPLS label field indicates the label to be used for forwarding, the route distinguisher field distinguishes between different VPN routes, and the IP prefix field contains the actual IP address range.Rate this question:
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- 9.
In a Layer 3 VPN environment using OSPF between the PE and CE routers, what attribute is always advertised to the remote PE router?
- A.
Route type
- B.
Domain ID
- C.
VPN route tag
- D.
Route origin
Correct Answer
A. Route typeExplanation
In a Layer 3 VPN environment using OSPF between the PE and CE routers, the attribute that is always advertised to the remote PE router is the "Route type". This attribute provides information about the type of route being advertised, such as whether it is an intra-area route, inter-area route, or external route. It helps the remote PE router determine the best path for forwarding traffic within the VPN network.Rate this question:
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- 10.
Which two statements are true when configuring a domain-id? (Choose two)
- A.
The default OSPF domain-id is 127.0.0.1
- B.
In most cases, a domain-id must be configured
- C.
In most cases, you don’t need to configure a domain-id
- D.
For a layer 3 VPN connecting multiple OSPF domains, configuring a domain-id can help control LSA translation.
Correct Answer(s)
C. In most cases, you don’t need to configure a domain-id
D. For a layer 3 VPN connecting multiple OSPF domains, configuring a domain-id can help control LSA translation.Explanation
The first statement, "In most cases, you don’t need to configure a domain-id," is true because OSPF automatically assigns a domain-id based on the router ID.
The fourth statement, "For a layer 3 VPN connecting multiple OSPF domains, configuring a domain-id can help control LSA translation," is true because when multiple OSPF domains are connected through a layer 3 VPN, configuring a domain-id helps in distinguishing between the different OSPF domains and controlling LSA translation between them.Rate this question:
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- 11.
When a CE and PE router are exchanging routes via EBGP sessions, which JUNOS software command on the PE router is useful for ensuring that the advertised routes are received by the CE routers?
- A.
As-loops
- B.
As-override
- C.
Local-as
- D.
Peer-as
Correct Answer
B. As-overrideExplanation
The "as-override" command on the PE router is useful for ensuring that the advertised routes are received by the CE routers. This command overrides the AS path information received from the EBGP neighbor and replaces it with the local AS number of the PE router. This allows the PE router to advertise the routes to the CE routers as if they were directly connected, preventing any potential routing issues caused by the AS path information.Rate this question:
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- 12.
How many bits is use for the VRF label associated with the Layer 3 VPN NLRI?
- A.
16 bits
- B.
18 bits
- C.
20 bits
- D.
24 bits
Correct Answer
D. 24 bitsExplanation
The VRF label associated with the Layer 3 VPN NLRI uses 24 bits. This means that it can have a total of 2^24 or 16,777,216 possible values. The VRF label is used to identify the specific VPN routing and forwarding table (VRF) that a particular VPN route belongs to. With 24 bits, there is enough range to accommodate a large number of VRFs in a network.Rate this question:
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- 13.
What are the two Route Distinguisher Types defined?
- A.
Type 2
- B.
Type 1
- C.
Type 3
- D.
Type 0
Correct Answer(s)
B. Type 1
D. Type 0Explanation
The two Route Distinguisher Types defined are Type 1 and Type 0. Type 1 is used for route distinguishers that are assigned by the service provider and are unique within their autonomous system. Type 0, on the other hand, is used for route distinguishers that are assigned by the customer and can be the same across multiple autonomous systems.Rate this question:
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- 14.
What controlles the PE-PE Route Distribution? (choose two)
- A.
VRF policy
- B.
OSPF tag
- C.
BGP extended community attributes
- D.
BGP local preference
Correct Answer(s)
A. VRF policy
C. BGP extended community attributesExplanation
The PE-PE Route Distribution is controlled by VRF policy and BGP extended community attributes. VRF policy allows for the separation of routing instances within a router, enabling different routing tables for different VPNs. BGP extended community attributes provide additional information about the route, such as the community it belongs to or the route's origin. Both of these factors play a crucial role in determining how routes are distributed between PE routers in a network.Rate this question:
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- 15.
What is the OSPF Domain-ID used for?
- A.
Allows for route-leaking
- B.
Only used on ASBR
- C.
Allows an administrator control LSA translation
- D.
None of the above
Correct Answer
C. Allows an administrator control LSA translationExplanation
The OSPF Domain-ID is used by an administrator to control LSA (Link State Advertisement) translation. LSA translation is the process of converting OSPFv3 LSAs into OSPFv2 LSAs or vice versa. By controlling LSA translation, administrators can ensure interoperability between OSPFv2 and OSPFv3 routers within the same OSPF domain. This allows for seamless communication and routing between routers using different versions of OSPF.Rate this question:
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- 16.
Which JUNOS software command automatically assigns a route target of target:64512:1234 to routes in a particular Layer 3 VRF table?
- A.
Vrf-import target:64512:1234
- B.
Vrf-export target:64512:1234
- C.
Vrf-target target:64512:1234
- D.
Vrf-route-target target:64512:1234
Correct Answer
C. Vrf-target target:64512:1234Explanation
The correct answer is "vrf-target target:64512:1234". This command is used in JUNOS software to automatically assign a route target of "target:64512:1234" to routes in a specific Layer 3 VRF table. The "vrf-target" command is specifically designed for this purpose, allowing for easy configuration and management of route targets in VRF tables.Rate this question:
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- 17.
Which JUNOS software configuration command allows PE routers to exchange routes in a Layer 3 VPN environment?
- A.
Family inet unicast
- B.
Family inet any
- C.
Family inet-vpn unicast
- D.
Family inet-vpn vpn-nlri
Correct Answer
C. Family inet-vpn unicastExplanation
The correct answer is "family inet-vpn unicast". This command allows PE routers to exchange routes in a Layer 3 VPN environment. The "family inet-vpn" command is specifically used for VPN (Virtual Private Network) configurations, and "unicast" specifies that only unicast routes will be exchanged. This ensures that the PE routers can properly communicate and exchange routing information within the VPN environment.Rate this question:
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- 18.
Which two mechanisms control route distribution between PE routers in an rfc 4364 VPN? (choose two)
- A.
Site ID
- B.
Policies
- C.
Circuit ID
- D.
Extended Communities
Correct Answer(s)
B. Policies
D. Extended CommunitiesExplanation
The two mechanisms that control route distribution between PE routers in an rfc 4364 VPN are policies and extended communities. Policies are used to define the specific rules and criteria for distributing routes between the PE routers. Extended communities are a set of attributes that provide additional information about the routes, allowing for more granular control and customization of route distribution. By utilizing both policies and extended communities, the PE routers can effectively control and manage the distribution of routes within the VPN network.Rate this question:
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- 19.
Which three attributes are advertised to the remote PWE and BGP-based VPNs? (choose three)
- A.
Circuit ID
- B.
VPN label
- C.
Route target
- D.
Route distinguisher
Correct Answer(s)
B. VPN label
C. Route target
D. Route distinguisherExplanation
The three attributes that are advertised to the remote PWE and BGP-based VPNs are VPN label, Route target, and Route distinguisher. The VPN label is used to identify the specific VPN that the traffic belongs to. The Route target is used to control the distribution of VPN routes among PE routers. The Route distinguisher is used to ensure that each customer has a unique set of VPN routes within the service provider's network.Rate this question:
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- 20.
In which two ways do MPLS layer3 VPNs support overlapping customer address spaces?
- A.
By implementing unique RDs for each customer
- B.
By implementing unique RTs for each customer
- C.
By implementing different LSPs for each customer
- D.
By implementing virtual routing spaces for each customer
Correct Answer(s)
A. By implementing unique RDs for each customer
D. By implementing virtual routing spaces for each customerExplanation
MPLS layer3 VPNs support overlapping customer address spaces by implementing unique Route Distinguishers (RDs) for each customer. RDs are used to distinguish between different VPNs and ensure that the same IP addresses can be used by different customers without conflicts. Additionally, MPLS layer3 VPNs also support overlapping customer address spaces by implementing virtual routing spaces for each customer. This allows multiple customers to use the same IP addresses within their own virtual routing space without causing any conflicts with other customers.Rate this question:
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- 21.
What are the two flows associated with RFC 4364 control information? (choose two)
- A.
Path flow
- B.
Control flow
- C.
Label Flow
- D.
Data flow
Correct Answer(s)
B. Control flow
D. Data flowExplanation
The two flows associated with RFC 4364 control information are control flow and data flow. Control flow refers to the flow of control information between the Provider Edge (PE) routers and the Route Reflectors (RRs) in a Multiprotocol Label Switching (MPLS) Virtual Private Network (VPN) network. This flow is responsible for exchanging routing information and maintaining the VPN routes. On the other hand, data flow refers to the flow of actual user data packets within the VPN network. These packets are encapsulated and forwarded based on the information obtained from the control flow.Rate this question:
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- 22.
What is the functionality of a OSPF Sham link?
- A.
Not an OSPF feature
- B.
Carries OSPF routes across backbone as BGP routes
- C.
VRF import
- D.
Security feature
Correct Answer
B. Carries OSPF routes across backbone as BGP routesExplanation
A Sham link is a feature in OSPF (Open Shortest Path First) that allows OSPF routes to be carried across a backbone network as BGP (Border Gateway Protocol) routes. This functionality is useful in scenarios where OSPF is used within individual areas of a network, but BGP is used to exchange routes between different areas or autonomous systems. The Sham link acts as a virtual link, connecting two OSPF areas through the backbone network, and allows OSPF routes to be exchanged as BGP routes, ensuring seamless connectivity and routing between different areas.Rate this question:
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- 23.
What is BGP Route refresh?
- A.
An extended community for layer 3 VPNs only
- B.
Avoids a MP-BGP session to be cleared after changes are made to the VPN membership.
- C.
Used to carry OSPF Metric values
- D.
Used with VRF import / export policies
Correct Answer
B. Avoids a MP-BGP session to be cleared after changes are made to the VPN membership.Explanation
BGP Route refresh is a mechanism that allows changes to be made to the VPN membership without clearing the MP-BGP session. This means that when changes are made to the VPN membership, the BGP session does not need to be reset or restarted, avoiding any disruption in connectivity. This is particularly useful in large-scale networks where frequent changes to the VPN membership may occur. By using BGP Route refresh, network administrators can ensure seamless and uninterrupted connectivity for their VPNs.Rate this question:
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Mar 17, 2023Quiz Edited by
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Mar 10, 2011Quiz Created by
Apalani
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