CCIE CCIE Service Provider 2 — Questions and Answers
Question 1: In BGP, what is the purpose of a Route Reflector (RR)?
- Connecting BGP to OSPF
- Eliminating the need for full IBGP mesh by reflecting routes to clients (Correct answer)
- Providing BGP authentication
- Encrypting BGP sessions
Correct 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.
Question 2: What is Segment Routing (SR) in modern service provider networks?
- A protocol for dividing networks into segments for security
- A source routing architecture using segments encoded in the packet header (Correct answer)
- A QoS mechanism for traffic segmentation
- VLAN segmentation for multi-tenant networks
Correct 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.
Question 3: Which protocol is commonly used in service provider cores for fast reroute and TE capabilities with Segment Routing?
- RIP
- IS-IS with SR extensions (Correct answer)
- EIGRP
- BGP only
Correct 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.
Question 4: In MPLS L2VPN VPLS, what is a VSI (Virtual Switching Instance)?
- A virtual router for L3VPN
- A virtual bridge that emulates a LAN across the MPLS backbone (Correct answer)
- A VLAN interface on a CE router
- A traffic engineering tunnel
Correct 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.
Question 5: What is the role of BGP confederations in large ISP networks?
- Combining multiple IGPs
- Dividing a large AS into sub-ASes to reduce IBGP full-mesh requirements (Correct answer)
- Providing route redundancy
- Enabling multicast routing
Correct 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.
Question 6: In a service provider network, what does the term 'P router' refer to?
- Provider edge router connecting to customer sites
- Core provider router that only handles MPLS label switching (Correct answer)
- Peering router connecting to other ISPs
- Primary router in a redundant pair
Correct 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.
CCIE CCIE Service Provider 2
In BGP, what is the purpose of a Route Reflector (RR)?