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Landing Zone Network Guide

6 Effective Routes and Longest Match

The routes used by VM traffic are the effective routes, a combination of system routes, UDR, and BGP routes. 0.0.0.0/0 is the last resort; more specific routes take priority.

View diagram Key points Back to overall map
Effective Routes and Longest Match
Diagram: Routing

Key points of this chapter

  • Viewing effective routes reveals the actual decisions
  • /24 and /16 take priority over 0.0.0.0/0
  • Use Network Watcher Next Hop to isolate issues
Azure virtual network traffic routing Network Watcher: Next hop overview
Explanation note

First explain the flow with a diagram, then supplement only the key points in text. For those unfamiliar with networking, showing where traffic flows before terminology is effective.

Longest match

For destination 203.0.113.2, when both 0.0.0.0/0 and 203.0.113.0/24 exist, the more specific 203.0.113.0/24 is chosen.

How to read Next Hop

Network Watcher's Next Hop shows the next-hop type, IP address, and route table ID for a destination IP. Use it to confirm whether the route is as intended.

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