What's changed: Created Professional Cloud Network Engineer Chapter 4 (Domain 4 "Hybrid/multicloud": Dedicated/Partner/Cross-Cloud Interconnect and VLAN attachments/L2-L3, HA VPN over Interconnect, 99.9%/99.99% SLA, MACsec, site-to-site IPSec VPN = HA VPN (on-prem/other VPC)/Classic VPN (route/policy-based), Cloud Router BGP attributes (ASN/MED/link-local/auth)/BFD/custom-advertised-learned routes/legacy-standard best-path selection, Network Connectivity Center hybrid spokes/site-to-site data transfer/router appliances/transitivity).
4.2Cloud Router and hybrid NCC
Understand Cloud Router BGP attributes (ASN, route priority/MED, link-local addresses, authentication), Bidirectional Forwarding Detection (BFD), custom-advertised/learned routes, VPC legacy/standard best-path selection, Network Connectivity Center hybrid spokes (VPN/VLAN attachments), site-to-site data transfer, router appliances (RAs), and solving transitivity issues.
Cloud Router is the heart of dynamic routing. Control paths with BGP attributes, and achieve transitive hybrid reachability with NCC.
4.2.1Cloud Router and BGP path control
Cloud Router exchanges routes dynamically with on-prem/other networks over BGP. Configure attributes: ASN (autonomous system number), route priority/MED for preference, link-local addresses for peering, and MD5 authentication. Detect link failures fast with BFD (Bidirectional Forwarding Detection). Control advertisements with custom-advertised routes (ranges advertised to on-prem) and custom-learned routes (ranges learned from on-prem). When multiple routes share a destination, selection follows the VPC best-path selection mode (legacy or standard). Map "fast failure detection = BFD" and "explicit advertised ranges = custom-advertised routes."
4.2.2Hybrid NCC and transitivity
Achieve transitive multi-site/hybrid connectivity with Network Connectivity Center. Connecting hybrid spokes (VPN tunnels or VLAN attachments) to the hub enables site-to-site data transfer between on-prem sites over the Google backbone. For SD-WAN, place a router appliance (RA) in the VPC and peer it with the NCC hub over BGP. Resolve transitivity issues caused by non-transitive VPC peering with NCC hub-and-spoke. Map "link sites via the cloud = site-to-site data transfer" and "integrate third-party SD-WAN into NCC = router appliance."
Common: requirement → means. E.g., "detect BGP link failure sub-second" = BFD; "explicit ranges advertised to on-prem" = custom-advertised routes; "control learned routes" = custom-learned routes; "link sites via the cloud" = NCC site-to-site data transfer; "integrate SD-WAN into NCC via BGP" = router appliance; "change route preference" = route priority/MED.
Watch the mix-ups: (1) Regional dynamic routing propagates BGP routes only within the same region—use global for all regions. (2) VPC peering is non-transitive—use NCC for multi-site transitive reach. (3) BFD speeds failure detection; path selection itself is decided by priority/MED.
4.2.3Section summary
- Cloud Router = BGP (ASN/priority-MED/auth); fast failure detection = BFD; control advertise/learn with custom routes
- Hybrid transitivity = NCC hybrid spokes; sites = site-to-site data transfer
- SD-WAN integration = router appliance; resolve non-transitive VPC peering with NCC
Sign in to track progress — Log in.
Quick check
(just a quick review)Q1. To detect a link failure between Cloud Router and a BGP peer sub-second and fail over fast, which do you enable?
Q2. To explicitly advertise extra IP ranges (beyond default subnets) from Cloud Router to on-prem, which do you use?
Q3. To interconnect two on-prem sites and transfer data over Google's backbone, which NCC capability?
Q4. To place a third-party SD-WAN appliance in the VPC and peer it with the NCC hub via BGP, which element?
Q5. Transitive reach for site A ⇄ Google ⇄ site B cannot be built with VPC peering alone. What is the best fix?
Keep track of your progress
The full study guide is free to read. Sign up free to practice with the question bank, track what you have read, review your mistakes, and highlight passages.