Podcast
Questions and Answers
What is MPLS generally referred to as?
What is MPLS generally referred to as?
What does MPLS use to make data forwarding decisions?
What does MPLS use to make data forwarding decisions?
What is the role of the customer edge switch in an MPLS-based Layer 2 VPN?
What is the role of the customer edge switch in an MPLS-based Layer 2 VPN?
What is one of the benefits of MPLS-based VPNs?
What is one of the benefits of MPLS-based VPNs?
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What is the format of traffic that is forwarded by the customer edge switch in an MPLS-based Layer 2 VPN?
What is the format of traffic that is forwarded by the customer edge switch in an MPLS-based Layer 2 VPN?
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What is the goal of MPLS in the context of Class of Service and Quality of Service?
What is the goal of MPLS in the context of Class of Service and Quality of Service?
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What is the advantage of using MPLS in terms of Layer 3 header analysis?
What is the advantage of using MPLS in terms of Layer 3 header analysis?
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What is the primary function of the provider edge switch in an MPLS-based Layer 2 VPN?
What is the primary function of the provider edge switch in an MPLS-based Layer 2 VPN?
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What is carried by MPLS over the service provider's network?
What is carried by MPLS over the service provider's network?
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Where does routing occur on a Layer 2 VPN?
Where does routing occur on a Layer 2 VPN?
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What must the CE switch select to send traffic in a Layer 2 VPN?
What must the CE switch select to send traffic in a Layer 2 VPN?
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What do the PE switches do with the customer's routes in a Layer 2 VPN?
What do the PE switches do with the customer's routes in a Layer 2 VPN?
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Who is responsible for configuring their own switches to carry all Layer 3 traffic in a Layer 2 VPN?
Who is responsible for configuring their own switches to carry all Layer 3 traffic in a Layer 2 VPN?
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What is the service provider's role in a Layer 2 VPN?
What is the service provider's role in a Layer 2 VPN?
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What is a Layer 2 circuit?
What is a Layer 2 circuit?
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What is required to connect each PE switch to each CE router or switch in a full-mesh Layer 2 VPN?
What is required to connect each PE switch to each CE router or switch in a full-mesh Layer 2 VPN?
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What is the primary benefit of Layer 2 VPNs for customers?
What is the primary benefit of Layer 2 VPNs for customers?
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What is the purpose of the VPN Forwarding Tables (VFTs) in Draft-Kompella?
What is the purpose of the VPN Forwarding Tables (VFTs) in Draft-Kompella?
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How are VCTs distributed in Draft-Kompella?
How are VCTs distributed in Draft-Kompella?
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What is the purpose of the DLCIs in Draft-Kompella?
What is the purpose of the DLCIs in Draft-Kompella?
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What is the difference between Draft-Kompella and Draft-Martini?
What is the difference between Draft-Kompella and Draft-Martini?
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What is the purpose of the VCTs in Draft-Kompella?
What is the purpose of the VCTs in Draft-Kompella?
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Which of the following is a supported Layer 2 technology in Draft-Kompella?
Which of the following is a supported Layer 2 technology in Draft-Kompella?
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What is the primary function of the PE device in Layer 2 VPNs?
What is the primary function of the PE device in Layer 2 VPNs?
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What is a requirement for a PE-CE layer 2 circuit?
What is a requirement for a PE-CE layer 2 circuit?
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What is the advantage of a service provider in Layer 3 VPN?
What is the advantage of a service provider in Layer 3 VPN?
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What is a characteristic of a Layer 2 VPN?
What is a characteristic of a Layer 2 VPN?
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What is a requirement for a CE switch in Layer 3 VPN?
What is a requirement for a CE switch in Layer 3 VPN?
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What is not supported in Layer 2 VPN?
What is not supported in Layer 2 VPN?
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What is the advantage of a customer in Layer 2 VPN?
What is the advantage of a customer in Layer 2 VPN?
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What is a characteristic of a service provider in Layer 3 VPN?
What is a characteristic of a service provider in Layer 3 VPN?
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What is not supported in the current implementation of Layer 2 VPN?
What is not supported in the current implementation of Layer 2 VPN?
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What is the IP address of the loopback interface on R1?
What is the IP address of the loopback interface on R1?
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What is the purpose of the 'mpls label protocol ldp' command?
What is the purpose of the 'mpls label protocol ldp' command?
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What is the IP address of the interface fa0/0 on R4?
What is the IP address of the interface fa0/0 on R4?
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What is the purpose of the 'xconnect' command?
What is the purpose of the 'xconnect' command?
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What is the IP address of the interface s1/0 on R2?
What is the IP address of the interface s1/0 on R2?
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What is the purpose of the 'mpls ip' command?
What is the purpose of the 'mpls ip' command?
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What is the IP address of the interface fa0/1 on R5?
What is the IP address of the interface fa0/1 on R5?
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What is the purpose of the 'mpls ldp router-id' command?
What is the purpose of the 'mpls ldp router-id' command?
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What happens to the traffic at the receiving site in a Layer 2 VPN?
What happens to the traffic at the receiving site in a Layer 2 VPN?
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What is the role of the PE switch in a Layer 2 VPN?
What is the role of the PE switch in a Layer 2 VPN?
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What is the purpose of a Layer 2 circuit?
What is the purpose of a Layer 2 circuit?
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How many logical interfaces are required for each site in a full-mesh topology?
How many logical interfaces are required for each site in a full-mesh topology?
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What is the responsibility of the customer in a Layer 2 VPN?
What is the responsibility of the customer in a Layer 2 VPN?
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What is the topology of the VPN determined by?
What is the topology of the VPN determined by?
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What is the benefit of a Layer 2 VPN for customers?
What is the benefit of a Layer 2 VPN for customers?
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What is the role of the service provider in a Layer 2 VPN?
What is the role of the service provider in a Layer 2 VPN?
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What is the primary function of the VPN Forwarding Tables (VFTs) in Draft-Kompella?
What is the primary function of the VPN Forwarding Tables (VFTs) in Draft-Kompella?
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What is used for Layer 2 Label Distribution in Draft-Martini?
What is used for Layer 2 Label Distribution in Draft-Martini?
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What is the purpose of the DLCIs in Draft-Kompella?
What is the purpose of the DLCIs in Draft-Kompella?
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What is a benefit of using MPLS-based Layer 2 VPNs?
What is a benefit of using MPLS-based Layer 2 VPNs?
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What is distributed by the PEs via MP-iBGP in Draft-Kompella?
What is distributed by the PEs via MP-iBGP in Draft-Kompella?
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What is a supported Layer 2 technology in Draft-Kompella?
What is a supported Layer 2 technology in Draft-Kompella?
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How are VCTs received in Draft-Kompella?
How are VCTs received in Draft-Kompella?
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What does the PE device do with the customer's routes in a Layer 2 VPN?
What does the PE device do with the customer's routes in a Layer 2 VPN?
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What is the primary difference between a Layer 2 circuit and a circuit cross-connect (CCC)?
What is the primary difference between a Layer 2 circuit and a circuit cross-connect (CCC)?
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What is the purpose of the VPN label advertised by the remote PE switch?
What is the purpose of the VPN label advertised by the remote PE switch?
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What is the signalling protocol used for advertising VPN labels?
What is the signalling protocol used for advertising VPN labels?
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What is the benefit of using MPLS-based Layer 2 VPNs for service providers?
What is the benefit of using MPLS-based Layer 2 VPNs for service providers?
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What is the primary benefit of using Layer 2 MPLS VPNs for customers?
What is the primary benefit of using Layer 2 MPLS VPNs for customers?
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What is the primary reason why providers are pushed to use two core networks?
What is the primary reason why providers are pushed to use two core networks?
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What is the primary advantage of using MPLS-based Layer 2 VPNs?
What is the primary advantage of using MPLS-based Layer 2 VPNs?
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What is the primary function of the PE switch in an MPLS-based Layer 2 VPN?
What is the primary function of the PE switch in an MPLS-based Layer 2 VPN?
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What is a requirement for a PE-CE layer 2 circuit?
What is a requirement for a PE-CE layer 2 circuit?
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What is not supported in the current implementation of Layer 2 VPN?
What is not supported in the current implementation of Layer 2 VPN?
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What is the primary function of the CE device in a Layer 2 VPN?
What is the primary function of the CE device in a Layer 2 VPN?
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What is an advantage of a Layer 2 VPN for customers?
What is an advantage of a Layer 2 VPN for customers?
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What is the format of traffic forwarded by the CE switch in a Layer 2 VPN?
What is the format of traffic forwarded by the CE switch in a Layer 2 VPN?
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What is a characteristic of a Layer 2 VPN?
What is a characteristic of a Layer 2 VPN?
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What is an advantage of a service provider in a Layer 3 VPN?
What is an advantage of a service provider in a Layer 3 VPN?
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What is necessary for CE devices at both ends in a Layer 2 VPN?
What is necessary for CE devices at both ends in a Layer 2 VPN?
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What is the primary goal of MPLS in terms of Class of Service and Quality of Service?
What is the primary goal of MPLS in terms of Class of Service and Quality of Service?
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How does the customer edge switch forward traffic in an MPLS-based Layer 2 VPN?
How does the customer edge switch forward traffic in an MPLS-based Layer 2 VPN?
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What is a benefit of using MPLS-based VPNs?
What is a benefit of using MPLS-based VPNs?
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What is the role of the provider edge switch in an MPLS-based Layer 2 VPN?
What is the role of the provider edge switch in an MPLS-based Layer 2 VPN?
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Which of the following is not a benefit of MPLS-based Layer 2 VPNs?
Which of the following is not a benefit of MPLS-based Layer 2 VPNs?
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What is the primary function of MPLS in an MPLS-based Layer 2 VPN?
What is the primary function of MPLS in an MPLS-based Layer 2 VPN?
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What is a standard for Layer 2 VPNs?
What is a standard for Layer 2 VPNs?
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What is the advantage of using MPLS-based VPNs for customers?
What is the advantage of using MPLS-based VPNs for customers?
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What is the primary function of the PE switch in a Martini-based Layer 2 VPN?
What is the primary function of the PE switch in a Martini-based Layer 2 VPN?
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What is distributed by the PE switch for each Layer 2 circuit in a Martini-based Layer 2 VPN?
What is distributed by the PE switch for each Layer 2 circuit in a Martini-based Layer 2 VPN?
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What is required for each PE-CE connection at both ends in a Martini-based Layer 2 VPN?
What is required for each PE-CE connection at both ends in a Martini-based Layer 2 VPN?
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What is used for label distribution in a Martini-based Layer 2 VPN?
What is used for label distribution in a Martini-based Layer 2 VPN?
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What type of label is used in a Martini-based Layer 2 VPN?
What type of label is used in a Martini-based Layer 2 VPN?
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What is the role of PE-2 in a Martini-based Layer 2 VPN?
What is the role of PE-2 in a Martini-based Layer 2 VPN?
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What is the relationship between BGP and LDP in a Martini-based Layer 2 VPN?
What is the relationship between BGP and LDP in a Martini-based Layer 2 VPN?
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What is the purpose of provisioning the CE in a Martini-based Layer 2 VPN?
What is the purpose of provisioning the CE in a Martini-based Layer 2 VPN?
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What is the purpose of the command 'xconnect 10.10.10.103 1 encapsulation mpls' on R3?
What is the purpose of the command 'xconnect 10.10.10.103 1 encapsulation mpls' on R3?
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What is the state of the LDP neighbor 10.10.10.103:0 (2) on R3?
What is the state of the LDP neighbor 10.10.10.103:0 (2) on R3?
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What is the destination IP address of the ping command on R4?
What is the destination IP address of the ping command on R4?
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What is the benefit of MPLS VPN for inter-site traffic?
What is the benefit of MPLS VPN for inter-site traffic?
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What is the destination IP address of the ping command on R5?
What is the destination IP address of the ping command on R5?
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What is the purpose of the command 'mpls label protocol ldp'?
What is the purpose of the command 'mpls label protocol ldp'?
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What is the state of the line protocol on the pseudowire interface on R3?
What is the state of the line protocol on the pseudowire interface on R3?
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What is the purpose of the command 'int fa0/0' on R3?
What is the purpose of the command 'int fa0/0' on R3?
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What is the purpose of the 'mpls label protocol ldp' command?
What is the purpose of the 'mpls label protocol ldp' command?
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What is the IP address of the interface fa0/0 on R4?
What is the IP address of the interface fa0/0 on R4?
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What is the purpose of the 'xconnect' command?
What is the purpose of the 'xconnect' command?
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What is the IP address of the loopback interface on R1?
What is the IP address of the loopback interface on R1?
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What is the purpose of the 'mpls ip' command?
What is the purpose of the 'mpls ip' command?
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What is the IP address of the interface fa0/1 on R5?
What is the IP address of the interface fa0/1 on R5?
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What is the purpose of the 'mpls ldp router-id' command?
What is the purpose of the 'mpls ldp router-id' command?
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What is the IP address of the interface s1/0 on R2?
What is the IP address of the interface s1/0 on R2?
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What is the primary goal of MPLS in packet-switched networks?
What is the primary goal of MPLS in packet-switched networks?
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What is the benefit of using MPLS-based VPNs in terms of Class of Service (CoS) and Quality of Service (QoS)?
What is the benefit of using MPLS-based VPNs in terms of Class of Service (CoS) and Quality of Service (QoS)?
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What is the format of traffic forwarded by the customer edge switch in an MPLS-based Layer 2 VPN?
What is the format of traffic forwarded by the customer edge switch in an MPLS-based Layer 2 VPN?
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What is the primary function of the provider edge switch in an MPLS-based Layer 2 VPN?
What is the primary function of the provider edge switch in an MPLS-based Layer 2 VPN?
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What is the benefit of using MPLS in terms of Layer 3 header analysis?
What is the benefit of using MPLS in terms of Layer 3 header analysis?
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What is the primary difference between MPLS-based Layer 2 VPNs and MPLS-based Layer 3 VPNs?
What is the primary difference between MPLS-based Layer 2 VPNs and MPLS-based Layer 3 VPNs?
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What is the advantage of using MPLS-based VPNs in terms of scalability?
What is the advantage of using MPLS-based VPNs in terms of scalability?
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What is the role of the Internet in the context of MPLS-based VPNs?
What is the role of the Internet in the context of MPLS-based VPNs?
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What is the primary function of the Provider Edge (PE) switch in a Layer 2 VPN?
What is the primary function of the Provider Edge (PE) switch in a Layer 2 VPN?
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What is required for a customer to configure in a Layer 2 VPN?
What is required for a customer to configure in a Layer 2 VPN?
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What determines the VPN topology in a Layer 2 VPN?
What determines the VPN topology in a Layer 2 VPN?
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What is the format of traffic sent by the Customer Edge (CE) switch in a Layer 2 VPN?
What is the format of traffic sent by the Customer Edge (CE) switch in a Layer 2 VPN?
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How many physical links are required to connect each PE switch to each CE router or switch in a full-mesh Layer 2 VPN?
How many physical links are required to connect each PE switch to each CE router or switch in a full-mesh Layer 2 VPN?
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What is the role of the service provider in a Layer 2 VPN?
What is the role of the service provider in a Layer 2 VPN?
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What is a Layer 2 circuit?
What is a Layer 2 circuit?
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What is the responsibility of the customer in a Layer 2 VPN?
What is the responsibility of the customer in a Layer 2 VPN?
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On which router is the 'xconnect' command configured?
On which router is the 'xconnect' command configured?
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What is the purpose of the 'mpls ldp router-id' command?
What is the purpose of the 'mpls ldp router-id' command?
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What is the benefit of using MPLS-based Layer 2 VPNs for customers?
What is the benefit of using MPLS-based Layer 2 VPNs for customers?
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What is the purpose of the 'mpls ip' command?
What is the purpose of the 'mpls ip' command?
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Which router has an IP address of 10.10.10.103 configured on its loopback interface?
Which router has an IP address of 10.10.10.103 configured on its loopback interface?
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What is the purpose of the 'mpls label protocol ldp' command?
What is the purpose of the 'mpls label protocol ldp' command?
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How many logical interfaces are required for each site in a full-mesh topology?
How many logical interfaces are required for each site in a full-mesh topology?
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What is the primary function of the VPN Forwarding Tables (VFTs) in Draft-Kompella?
What is the primary function of the VPN Forwarding Tables (VFTs) in Draft-Kompella?
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What is the primary function of the 'xconnect' command in an MPLS-based Layer 2 VPN?
What is the primary function of the 'xconnect' command in an MPLS-based Layer 2 VPN?
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What is the benefit of using MPLS-based Layer 2 VPNs for inter-site traffic?
What is the benefit of using MPLS-based Layer 2 VPNs for inter-site traffic?
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What is the role of the PE device in an MPLS-based Layer 2 VPN?
What is the role of the PE device in an MPLS-based Layer 2 VPN?
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What is the purpose of the LDP protocol in an MPLS-based Layer 2 VPN?
What is the purpose of the LDP protocol in an MPLS-based Layer 2 VPN?
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What is the primary function of a Layer 2 circuit in an MPLS-based Layer 2 VPN?
What is the primary function of a Layer 2 circuit in an MPLS-based Layer 2 VPN?
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What is the advantage of using MPLS-based Layer 2 VPNs for customers?
What is the advantage of using MPLS-based Layer 2 VPNs for customers?
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What is the role of the CE device in an MPLS-based Layer 2 VPN?
What is the role of the CE device in an MPLS-based Layer 2 VPN?
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What is the primary function of the VPN forwarding tables in an MPLS-based Layer 2 VPN?
What is the primary function of the VPN forwarding tables in an MPLS-based Layer 2 VPN?
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What is the primary function of the VPN Forwarding Tables (VFTs) in Draft-Kompella?
What is the primary function of the VPN Forwarding Tables (VFTs) in Draft-Kompella?
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What is the primary function of the PE switch in a Layer 2 VPN?
What is the primary function of the PE switch in a Layer 2 VPN?
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Which of the following is NOT a supported Layer 2 technology in Draft-Kompella?
Which of the following is NOT a supported Layer 2 technology in Draft-Kompella?
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What is the purpose of distributing VCTs in Draft-Kompella?
What is the purpose of distributing VCTs in Draft-Kompella?
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What is the format of traffic that is sent by the PE switch across the service provider's network?
What is the format of traffic that is sent by the PE switch across the service provider's network?
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What is the primary benefit of Layer 2 MPLS VPNs for customers?
What is the primary benefit of Layer 2 MPLS VPNs for customers?
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What is the benefit of a Layer 2 VPN for customers?
What is the benefit of a Layer 2 VPN for customers?
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How are VCTs distributed in Draft-Kompella?
How are VCTs distributed in Draft-Kompella?
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What determines the VPN topology in a Layer 2 VPN?
What determines the VPN topology in a Layer 2 VPN?
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What is the purpose of the DLCIs in Draft-Kompella?
What is the purpose of the DLCIs in Draft-Kompella?
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What is required to connect each PE switch to each CE router or switch in a full-mesh Layer 2 VPN?
What is required to connect each PE switch to each CE router or switch in a full-mesh Layer 2 VPN?
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What is the role of the customer edge switch in a Layer 2 VPN?
What is the role of the customer edge switch in a Layer 2 VPN?
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What is the main difference between Draft-Kompella and Draft-Martini?
What is the main difference between Draft-Kompella and Draft-Martini?
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How does the PE device map the circuit ID to an MPLS LSP in a Layer 2 VPN?
How does the PE device map the circuit ID to an MPLS LSP in a Layer 2 VPN?
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What is a Layer 2 circuit?
What is a Layer 2 circuit?
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What is the responsibility of the service provider in a Layer 2 VPN?
What is the responsibility of the service provider in a Layer 2 VPN?
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In a Layer 2 VPN, what is required for a PE-CE layer 2 circuit?
In a Layer 2 VPN, what is required for a PE-CE layer 2 circuit?
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What is not supported in the current implementation of Layer 2 VPN?
What is not supported in the current implementation of Layer 2 VPN?
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What is the role of the service provider in a Layer 3 VPN?
What is the role of the service provider in a Layer 3 VPN?
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What is the benefit of a Layer 2 VPN for customers?
What is the benefit of a Layer 2 VPN for customers?
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How does the CE switch forward traffic in a Layer 2 VPN?
How does the CE switch forward traffic in a Layer 2 VPN?
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What is the primary benefit of a Layer 3 VPN for service providers?
What is the primary benefit of a Layer 3 VPN for service providers?
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What is required for the CE switch in a Layer 3 VPN?
What is required for the CE switch in a Layer 3 VPN?
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What is the primary difference between Layer 2 VPN and Layer 3 VPN?
What is the primary difference between Layer 2 VPN and Layer 3 VPN?
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Study Notes
MPLS-Based Layer 2 VPNs
- MPLS (Multi-Protocol Label Switching) is a data-carrying mechanism that operates between Layer 2 (data link layer) and Layer 3 (network layer or IP Layer), also referred to as a "Layer 2.5" protocol.
- MPLS provides a unified data-carrying service for both circuit-based clients and packet-switching clients, offering a datagram service model.
- MPLS can carry various types of traffic, including IP packets, native ATM, SONET, and Ethernet frames.
MPLS-Layer 2 VPN
- In an MPLS-based Layer 2 VPN, traffic is forwarded by the customer's CE (customer edge) switch or router to the service provider's PE (provider edge) switch in a Layer 2 format.
- The traffic is carried by MPLS over the service provider's network and then converted back to Layer 2 format at the receiving site.
- Routing occurs on the customer's switches, typically on the CE switch.
Layer 2 Circuits
- A Layer 2 circuit is a point-to-point Layer 2 connection that uses MPLS or another tunneling technology on the service provider's network.
- In Layer 2 VPNs, customers maintain control over most of the administration of their networks, including own routing policies.
Layer 2 VPN Standards
- Two proposals for MPLS-based Layer 2 VPNs: Draft-Kompella and Draft-Martini.
- Draft-Kompella uses MP-iBGP for Layer 2 VPN label distribution, while Draft-Martini uses LDP for Layer 2 Label Distribution.
Draft-Kompella
- Uses VPN Forwarding Tables (VFTs) and VPN Connection Tables (VCTs) to distribute labels and configure VPN topologies.
- VFTs are populated with information provisioned for the local CE, including circuit ID, inner label, and outer label.
- VCTs are received from other PEs via MP-iBGP and are used to configure VPN topologies.
Draft-Martini
- Uses LDP for signalling in the provider's network.
- VLAN ID must be the same at both ends (PE-CE layer 2 circuit).
- Frame Relay and ATM AAL5 encapsulations are not supported.
- CE devices at both ends should be configured for routing to carry Layer 3 traffic.
Comparison between MPLS-Based Layer 2 VPN and Layer 3 VPN
-
Layer 2 VPN: customer sites appear to be on the same LAN, even if geographically dispersed; customer has complete control over policies and routing.
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Layer 3 VPN: service provider determines policies and routing; customer must share information about their network topology.### Configuration of MPLS Layer 2 VPN using Ethernet as Layer 2 Transport
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Configuration on customer routers R4 and R5 involves setting up IP addresses and RIP version 2 on interfaces fa0/0 and fa0/1.
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R4 and R5 have IP addresses 172.16.0.9 and 172.16.0.10 respectively on interface fa0/0, and 192.168.1.1 and 192.168.2.1 respectively on interface fa0/1.
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RIP version 2 is enabled with networks 192.168.1.0 and 172.16.0.8 on R4, and networks 192.168.2.0 and 172.16.0.8 on R5.
Configuration on ISP Routers R1, R2, and R3
- R1, R2, and R3 are configured with IP addresses on loopback 0 (10.10.10.103, 10.10.10.104, and 10.10.10.105 respectively), and on serial interfaces s1/0 (172.16.0.2, 172.16.0.1, and 172.16.1.2 respectively).
- OSPF is enabled with area 0 on all three routers.
- MPLS is enabled with label protocol LDP on all three routers.
- MPLS label ranges are set to 100-199 on R1, 200-299 on R2, and 300-399 on R3.
Configuration of MPLS Layer 2 VPN Virtual Circuit using Pseudo-wire Technology
- On router R1, a virtual circuit is set up using xconnect with the peer 10.10.10.105 and encapsulation MPLS.
- The pseudowire interface is brought up, and the configuration is saved.
MPLS-Based Layer 2 VPNs
- A Layer 2 circuit is similar to a circuit cross-connect (CCC), but multiple Layer 2 circuits can be transported over a single label-switched path (LSP) tunnel between two provider edge (PE) switches.
- In contrast, each CCC requires a dedicated LSP.
- Junos OS implementation of Layer 2 circuits only supports remote forms of Layer 2 circuits, i.e., connections from a local customer edge (CE) switch to a remote CE switch.
- Packets are sent to the remote CE switch using an egress VPN label advertised by the remote PE switch, which transits over an RSVP or LDP LSP tunnel to the remote PE switch connected to the remote CE switch.
- LDP is the signalling protocol used for advertising VPN labels.
Layer 2 Provider-Provisioned VPNs
- Providers used to use a single ATM core to support Internet and VPN traffic, but ATM is not fast enough to support Internet traffic.
- Providers are pushed to have two core networks, but why not support both over an MPLS core?
- Map Frame Relay and ATM to MPLS LSPs, as L3 VPNs can also be over the same core.
Benefits of Layer 2 MPLS
- Service providers do not have to invest in separate Layer 2 devices to provide Layer 2 VPN service.
- The same PE router can run Layer 3 VPNs as well as Layer 2 VPNs.
- A Layer 2 MPLS VPN allows customers to use their existing Layer 2 VPN service over an MPLS backbone.
MPLS-Based Layer 2 VPN Configuration
- Learning objectives include understanding MPLS L2 VPN, provider provisioned VPN, benefits of Layer 2 VPN, standards for Layer 2 VPN, comparison between MPLS L2 & L3 VPN, and MPLS-based VPN configuration.
Introduction to MPLS
- Multi Protocol Label Switching (MPLS) is a data-carrying mechanism in packet-switched networks that operates at a TCP/IP layer considered to be between traditional definitions of Layer 2 (data link layer) and Layer 3 (network layer or IP Layer), and thus is often referred to as a "Layer 2.5" protocol.
- MPLS was designed to provide a unified data-carrying service for both circuit-based clients and packet-switching clients, which provide a datagram service model.
- MPLS can be used to carry many different kinds of traffic, including IP packets, as well as native ATM, SONET, and Ethernet frames.
MPLS-Layer 2 VPN
- In an MPLS-based Layer 2 VPN, traffic is forwarded by the customer's CE switch to the service provider's PE switch in a Layer 2 format.
- It is carried by MPLS over the service provider's network and then converted back to Layer 2 format at the receiving site.
- On a Layer 2 VPN, routing occurs on the customer's switches, typically on the CE switch.
Layer 2 Circuits
- A Layer 2 circuit is a point-to-point Layer 2 connection that uses MPLS or another tunneling technology on the service provider's network.
- VLAN ID must be the same at both ends (PE-CE Layer 2 circuit).
- Frame Relay & ATM AAL5 encapsulations are not supported at present.
- CE devices at both ends should be configured for routing to carry Layer 3 traffic.
Comparison between MPLS-Based Layer 2 VPN & Layer 3 VPN
- In a Layer 2 VPN, the customer has complete control over policies and routing, while in a Layer 3 VPN, the service provider determines the policies and routing.
- In a Layer 2 VPN, the CE switch forwards traffic to the service provider's PE switch in a Layer 2 format, while in a Layer 3 VPN, the customer's CE switch must be configured to use BGP or OSPF to communicate with the service provider's PE switch to carry IP prefixes across the network.
Layer 2 VPN Standards
- There are two proposals for MPLS-based Layer 2 VPNs: Draft-Kompella (uses MP-iBGP for Layer 2 VPN label distribution) and Draft-Martini (uses LDP for Layer 2 Label Distribution).
Draft-Kompella and Draft-Martini Overview
- Draft-Kompella uses MP-iBGP for label distribution and has VPN Forwarding Tables (VFTs) and VPN Connection Tables (VCTs).
- Draft-Martini uses LDP for signalling in the provider's network and supports Frame Relay, ATM AAL5 CPCS Mode, ATM Transparent Cell Mode, Ethernet, Ethernet VLAN, Cisco HDLC, and PPP.
MPLS-Based Layer 2 VPNs
Learning Objectives
- Understand MPLS L2 VPN
- Understand provider-provisioned VPN
- Know the benefits of Layer 2 VPN
- Understand the standards for Layer 2 VPN
- Compare MPLS L2 VPN with L3 VPN
- Configure MPLS-based VPN
Introduction to MPLS
- MPLS is a data-carrying mechanism in packet-switched networks
- It operates at a TCP/IP layer between traditional definitions of Layer 2 and Layer 3
- MPLS is often referred to as a "Layer 2.5" protocol
- It provides a unified data-carrying service for both circuit-based and packet-switching clients
- MPLS can carry many different kinds of traffic, including IP packets, ATM, SONET, and Ethernet frames
MPLS-Layer 2 VPN
- In an MPLS-based Layer 2 VPN, traffic is forwarded by the customer's CE switch to the service provider's PE switch in a Layer 2 format
- Traffic is carried by MPLS over the service provider's network and then converted back to Layer 2 format at the receiving site
- Routing occurs on the customer's switches, typically on the CE switch
- The CE switch must select the appropriate circuit on which to send traffic
Layer 2 Circuits
- A Layer 2 circuit is a point-to-point Layer 2 connection that uses MPLS or another tunneling technology on the service provider's network
- Since LDP is used, BGP is not required
- Only like circuits are allowed between PE-CE at both ends
- Inner label is defined as Virtual Circuit Label (VC Label)
- Martini-VC Label Distribution is used to distribute VC labels for each Layer 2 circuit
Configuration of MPLS Layer 2 VPN
- Configure Layer 2 circuit IDs one each for remote CE device
- Configuration involves setting up IP addresses, routing, and MPLS on the routers
Configuration of MPLS Layer 2 VPN using Ethernet as Layer 2 Transport
- Configuration involves setting up IP addresses, routing, and MPLS on the routers
- Routers R4, R5, R1, R2, and R3 are configured with IP addresses, routing, and MPLS
Configuration of MPLS Layer 2 VPN Virtual Circuit using Pseudo-wire Technology
- Configuration involves setting up xconnect on the routers
- On Router R1, xconnect is configured to connect to Router R3
- On Router R3, xconnect is configured to connect to Router R1
Observations
- Ping tests are successful between routers R4, R5, and R1, R2, and R3
Conclusion
- MPLS VPN provides optimal routing for traffic belonging to the customer for inter-site traffic
MPLS-Based Layer 2 VPNs
- MPLS VPN provides optimal routing for inter-site traffic.
- Configuration of MPLS Layer 2 VPN using Ethernet as Layer 2 transport:
- On customer routers R4 and R5:
- Configure IP addresses and routing information.
- Enable RIP and configure network commands.
- On ISP routers R1, R2, and R3:
- Configure IP addresses, OSPF routing, and MPLS labels.
- Enable CEF and MPLS IP.
- On customer routers R4 and R5:
Configuration of MPLS Layer 2 VPN Virtual Circuit using Pseudo-wire Technology
- On Router R1:
- Configure xconnect command to establish a pseudo-wire connection to Router R3.
- On Router R3:
- Configure xconnect command to establish a pseudo-wire connection to Router R1.
MPLS Layer 2 VPN Overview
- In a Layer 2 VPN, routing occurs on the customer's switches.
- The customer's CE switch selects the appropriate circuit to send traffic.
- The PE switch sends traffic across the service provider's network to the PE switch connected to the receiving site.
- The service provider must detect the amount of traffic the Layer 2 VPN will carry.
Layer 2 Circuits
- A Layer 2 circuit is a point-to-point Layer 2 connection that uses MPLS or another tunneling technology on the service provider's network.
- In Layer 2 VPNs, customers can maintain control over most of their network administration.
Layer 2 VPN Standards
- Two proposals for MPLS-based Layer 2 VPNs: Draft-Kompella and Draft-Martini.
- Draft-Kompella uses MP-iBGP for Layer 2 VPN label distribution.
- Draft-Martini uses LDP for Layer 2 label distribution.
Draft-Kompella
- Uses VPN Forwarding Tables (VFTs) and VPN Connection Tables (VCTs).
- VFTs are populated with CE information and VCTs are distributed to PEs via MP-iBGP.
- Provisioning customer site on PE involves configuring DLCIs and VFTs.
Draft-Kompella Data Flow
- Packet flow involves IGP label, site label, and DLCI lookup.
Draft-Kompella Supported Layer 2 Technologies
-
Frame Relay
-
ATM AAL5 CPCS mode
-
ATM Transparent Cell mode
-
Ethernet
-
Ethernet VLAN
-
Cisco HDLC
-
PPP### MPLS-Based Layer 2 VPN Requirements
-
VLAN ID must be the same at both ends of the PE-CE layer 2 circuit
-
CE devices at both ends must be configured for routing to carry layer 3 traffic
-
Frame Relay and ATM AAL5 encapsulations are not supported
Comparison of MPLS-Based Layer 2 VPN and Layer 3 VPN
Layer 2 VPN
- Customer sites appear to be on the same LAN, even if geographically dispersed
- Customer has complete control over policies and routing
- CE switch forwards traffic to the service provider's PE switch in Layer 2 format
Layer 3 VPN
- Service provider's technical expertise ensures efficient site-to-site routing
- Service providers can provide additional value-added services through network convergence that encompasses voice, video, and data
- Service provider determines policies and routing
- Customer's CE switch must be configured to use BGP or OSPF to communicate with the service provider's PE switch to carry IP prefixes across the network
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Learn about MPLS-based Layer 2 VPNs, provider provisioned VPN, benefits, standards, and configuration. Compare MPLS L2 and L3 VPN and understand MPLS based VPN Configuration.