Unified AS Routing Policy | Generated by AI
Question: What term fills the blank — an Autonomous System (AS) may use multiple internal routing protocols and metrics, but it presents a ____ and consistent routing policy to other ASes?
Answer:
The answer is 单一的 (single / unified).
Explanation
An Autonomous System (AS) is defined as a collection of IP networks and routers under the control of a single administrative entity. The key principle is:
Internally, an AS can be very complex:
- It may run multiple Interior Gateway Protocols (IGPs) such as OSPF, EIGRP, RIP, or IS-IS.
- It can use different metrics (hop count, bandwidth, delay, cost, etc.) for internal route selection.
- It can have thousands of routers with varying configurations.
Externally, however, an AS must present itself as a single, unified entity:
-
An autonomous system (AS) is a large network or group of networks that has a unified routing policy. Every computer or device that connects to the Internet is connected to an AS.
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An Autonomous System (AS) is a collection of IP networks and routers under the control of a single entity, presenting a unified routing policy to the internet.
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An AS is a network or a collection of connected IP routing prefixes under the control of one or multiple network operators that present a common routing policy to the internet.
This “single/unified” routing policy is what the AS advertises to other ASes via BGP (Border Gateway Protocol) — the exterior gateway protocol used between different ASes on the Internet.
Why is this important?
| Aspect | Internal (Inside AS) | External (To other ASes) |
|---|---|---|
| Routing Protocol | Multiple IGPs (OSPF, RIP, EIGRP…) | Single EGP (BGP) |
| Routing Policy | Can vary by region/department | One unified policy |
| Metrics | Different per protocol | Abstracted into BGP attributes |
| Identity | Many routers, many subnets | One ASN (e.g., AS13335) |
Policy decisions (such as preferring certain network paths, accepting or rejecting routes from specific sources) remain internal to the AS and invisible to external systems. This is what allows the Internet to scale — each AS handles its own internal complexity and only exposes a clean, single routing policy outward.
Therefore, the blank should be filled with: 单一的 (single)
References:
- Cloudflare — What is an Autonomous System?
- Kentik — BGP Routing Tutorial
- CacheFly — BGP Routing Guide
- JumpCloud — What is an Autonomous System?