CCIE Service Provider Flashcards

In BGP, what is the purpose of a Route Reflector (RR)?

Answer: Eliminating the need for full IBGP mesh by reflecting routes to clients

Route Reflectors allow BGP routes received from one client to be reflected to other clients, eliminating the scalability problem of requiring full IBGP mesh.

What is Segment Routing (SR) in modern service provider networks?

Answer: A source routing architecture using segments encoded in the packet header

Segment Routing (SR) is a source-routing architecture where the ingress node encodes an explicit path as a list of segments (SIDs) in the packet header.

Which protocol is commonly used in service provider cores for fast reroute and TE capabilities with Segment Routing?

Answer: IS-IS with SR extensions

IS-IS with SR extensions distributes Node SIDs and Adjacency SIDs throughout the SP core, enabling SR-based traffic engineering and TI-LFA fast reroute.

In MPLS L2VPN VPLS, what is a VSI (Virtual Switching Instance)?

Answer: A virtual bridge that emulates a LAN across the MPLS backbone

A VSI (Virtual Switching Instance) in VPLS emulates a multi-point Ethernet LAN across the MPLS backbone by maintaining MAC address tables per service.

What is the role of BGP confederations in large ISP networks?

Answer: Dividing a large AS into sub-ASes to reduce IBGP full-mesh requirements

BGP confederations split a large AS into smaller sub-ASes, with EBGP running between sub-ASes, reducing the full IBGP mesh required in the overall AS.

In a service provider network, what does the term 'P router' refer to?

Answer: Core provider router that only handles MPLS label switching

P (Provider) routers are core MPLS routers that only perform label switching; they have no VRFs or customer routing knowledge, unlike PE routers.