Provider Edge Bridge Functions for Implementing Provider Bridging

Functions of a Provider Edge Bridge in Provider Bridging

Q: What are three functions of a provider edge bridge when implementing provider bridging? (Choose three.)

to forward IEEE 802.1Q frames to customersto encapsulate customer frames using the IEEE 802.1ad formatto forward customer frames across a provider bridged network

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Question

What are three functions of a provider edge bridge when implementing provider bridging? (Choose three.)

Answers

A. to forward frames based only on the S-VLAN tag

B. to encapsulate customer frames and append a C-VLAN tag

C. to forward IEEE 802.1Q frames to customers

D. to encapsulate customer frames using the IEEE 802.1ad format

E. to forward customer frames across a provider bridged network

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Explanations

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A. B. C. D. E.

CDE

A provider network can provide Layer 2 forwarding services for customers wishing to connect their remote sites together. The provider uses 802.1ad double- tagged (S-tag, C-tag) frames across their network and delivers the 802.1Q frames to the customer network at the remote end.

Provider bridging, also known as QinQ (or IEEE 802.1ad) is a method used to extend VLANs across multiple service provider networks. In this scenario, the Provider Edge (PE) bridge is a critical component that is responsible for forwarding customer traffic across the service provider network. Below are the three functions of a Provider Edge bridge when implementing Provider Bridging:

Encapsulate customer frames and append a C-VLAN tag: The PE bridge needs to add a Customer VLAN (C-VLAN) tag to the customer frames received from the customer edge (CE) equipment. This C-VLAN tag will help to identify the customer's VLAN on the service provider's network.
Forward customer frames across a provider bridged network: The PE bridge is responsible for forwarding customer frames between CE devices across the service provider network. This is accomplished by analyzing the C-VLAN tag and forwarding the frame to the appropriate destination port on the other side of the service provider network.
Encapsulate customer frames using the IEEE 802.1ad format: The PE bridge uses the IEEE 802.1ad standard to encapsulate customer frames. This standard allows the PE bridge to add a second VLAN tag, called the Service VLAN (S-VLAN) tag, to the customer frame. This S-VLAN tag is used to identify the VLAN that is associated with the service provided by the service provider network. The combination of the C-VLAN and S-VLAN tags is used to extend VLANs across the provider network.

Therefore, the correct answers are B, E, and D. The PE bridge encapsulates customer frames and appends a C-VLAN tag, forwards customer frames across a provider bridged network, and encapsulates customer frames using the IEEE 802.1ad format.

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