Top L2VPN Interview Questions (2024)
What is an L2VPN?
What is VPLS?
What is EVPN?
What are the different types of L2VPNs?
What is a pseudowire?
What are the advantages of using L2VPNs?
How does a pseudowire work?
What is the purpose of a VPLS bridge domain?
How does EVPN handle MAC learning and distribution?
What is the purpose of the split-horizon forwarding mechanism in VPLS?
What is the difference between a Martini draft and a Kompella draft in VPLS?
What are the scalability considerations for deploying L2VPNs?
What is the purpose of the BGP Ethernet VPN (EVPN) route type 2?
How does EVPN support multihoming?
How does VPLS handle unknown unicast traffic?
Q: What is an L2VPN?
Ans:
Layer 2 Virtual Private Network is referred to as L2VPN. It is a technique that allows Layer 2 connectivity to be extended across a wide area network (WAN) or the Internet, enabling different locations to communicate as if they were on the same local network.
Q: What is VPLS?
Ans:
The L2VPN technology VPLS (Virtual Private LAN Service) is based on Ethernet. It permits shared IP/MPLS connections across numerous sites while keeping appearance of a single LAN. Ethernet frames are transported between locations using VPLS using MPLS.
Q: What is EVPN?
Ans:
An advanced L2VPN technology that offers scalable and effective Ethernet-based communication is called EVPN (Ethernet VPN). EVPN is appropriate for large-scale deployments since it makes use of BGP (Border Gateway Protocol) as the control plane to deliver MAC (Media Access Control) and IP routing information.
Q: What are the different types of L2VPNs?
Ans:
L2VPNs come in the following main types:
- Virtual Private LAN Service (VPLS) and Ethernet VPN (EVPN) are two examples of Ethernet-based L2VPNs.
- Frame Relay and ATM-based L2VPNs: These offer Layer 2 connectivity using legacy technologies like Frame Relay and ATM.
Checkout our related posts :
Q: What is a pseudowire?
Ans:
In L2VPNs, a pseudowire is a device that simulates a point-to-point link over a packet-switched network. Through the service provider network, it transports Layer 2 frames between customer edge (CE) devices.
Q: What are the advantages of using L2VPNs?
Ans:
L2VPNs have a number of benefits, such as:
- Layer 2 networks can be extended seamlessly between different sites.
- Helps with multicast traffic.
- Maintaining the Layer 2 apps and protocols already in use.
- Effective use of the bandwidth.
- Simplicity in network management and configuration.
Q: How does a pseudowire work?
Ans:
Layer 2 frames are encapsulated within IP or MPLS packets to create a pseudowire. The decapsulated frames are subsequently sent to the remote location across the provider network, where they are delivered to the proper CE device.
Q: What is the purpose of a VPLS bridge domain?
Ans:
A Layer 2 broadcast domain within a VPLS network is logically represented by a VPLS bridge domain. It establishes the group of CE devices that are associated with the same Layer 2 domain and permits intercommunication between them.
Q: How does EVPN handle MAC learning and distribution?
Ans:
To distribute MAC reachability information across the network, EVPN makes use of the BGP control plane. Each PE (Provider Edge) device uses BGP to advertise the MAC addresses it has picked up from the CE devices it is connected to, enabling other PEs to acquire and keep up MAC-to-IP mappings.
Q: What is the purpose of the split-horizon forwarding mechanism in VPLS?
Ans:
To avoid network loops, VPLS uses a method called split-horizon forwarding. In order to prevent unwanted flooding and risky loops, it makes sure that a received frame is not transmitted back to the site from which it came.
Q: What is the difference between a Martini draft and a Kompella draft in VPLS?
Ans:
Two alternative draft that outline how VPLS is put into use are Martini and Kompella. The primary distinction is in the control protocol and signaling used. While the Kompella draft uses BGP for signaling and MPLS for label distribution, the Martini draft uses LDP (Label Distribution Protocol) for signaling.
Q: What are the scalability considerations for deploying L2VPNs?
Ans:
Scalability factors for L2VPN deployments include the numbers of sites, the volume of traffic, the number of MAC addresses, and the provider network's capacity. By lowering the amount of flooding and control plane overhead, technologies like hierarchical VPLS and EVPN could help in enhancing scalability.
Q: What is the purpose of the BGP Ethernet VPN (EVPN) route type 2?
Ans:
Within an EVPN network, MAC reachability information is advertised using BGP EVPN route type 2. It carries the destination MAC address, any related IP addresses, and the MPLS label that is used to relay traffic to the MAC address.
Q: How does EVPN support multihoming?
Ans:
A CE device can connect to numerous PEs for redundancy according to the multihoming methods offered by EVPN. With its support for active-active and active-passive multihoming modes, EVPN offers capabilities for load balancing and link protection.
Q: How does VPLS handle unknown unicast traffic?
Ans:
In VPLS, all sites inside the VPLS domain receive a flood of unknown unicast traffic, with the exception of the site from where the traffic originated. This flooding enables all traffic, including any possible new MAC addresses, to go to the proper address.