As mentioned, the two basic types of routing protocols are distance vector and link state. OSPF is an example of a link-state routing protocol.
如前所述，路由協定的兩種基本類型是距離向量與鏈路狀態。OSPF 是鏈路狀態路由協定的一個範例。
Although most routing protocols belong to these two types, the Cisco proprietary EIGRP routing protocol is an exception and is considered as an advanced distance vector protocol. The reason is it contains some properties of distance vector and some properties of link state protocols. Despite the fact that it is based on the architecture of the distance vector protocols, some of the implemented link state features play a key role in the protocol behavior. For example, EIGRP uses Hello packets to discover neighbors, multiple parameters are included in the metric (value) calculation for the routes, it uses incremental updates, and so on.
雖然大多數路由協定都屬於這兩種類型，但 Cisco 專屬的 EIGRP 路由協定是個例外，被視為進階距離向量協定。原因是它同時包含距離向量與鏈路狀態協定的部分特性。儘管其架構基礎是距離向量協定，但它所實作的一些鏈路狀態特性，在協定行為中扮演了關鍵角色。舉例來說，EIGRP 使用 Hello 封包來探索鄰居，度量值（數值）的計算中包含多項參數，並且使用增量更新等等。
When a failure occurs in a network, routing protocols should detect the failure as soon as possible and find another path across the network. Link-state protocols support fast convergence with support for scalability and multivendor environments so they are the usual type of IGP that is found in large network environments. (As noted, EIGRP can also be used in large networks and one of the benefits it offers is the fast convergence time).
當網路發生故障時，路由協定應盡快偵測到該故障，並找出穿越網路的另一條路徑。鏈路狀態協定支援快速收斂，同時具備可擴充性並支援多廠商環境，因此它們是大型網路環境中常見的 IGP 類型。（如前所述，EIGRP 也可用於大型網路，其優點之一就是收斂時間快。）
The link-state protocols consist of the following key features:
鏈路狀態協定具有下列幾項關鍵特性：
- They are scalable:Link-state protocols use a hierarchical design and can scale to very large networks, if properly designed.具可擴充性：鏈路狀態協定採用階層式設計，若設計得當，可擴充至非常大型的網路。
- Each router has a full map of the topology:Because each router contains full information about the routers and links in a network, each router is able to independently select a loop-free and efficient pathway, which is based on cost, to reach every neighbor in the network.每台路由器都擁有完整的拓樸地圖：由於每台路由器都包含網路中所有路由器與鏈路的完整資訊，因此每台路由器都能根據成本，獨立選出一條無迴圈且高效的路徑，通往網路中的每個鄰居。
- Updates are sent when a topology change occurs and are reflooded periodically: Link-state protocols send updates of a topology change by using triggered updates. Also, updates are sent periodically—by default every 30 minutes.當拓樸發生變化時會發送更新，並會定期重新泛洪：鏈路狀態協定會使用觸發式更新來發送拓樸變化的更新。此外，更新也會定期發送，預設每 30 分鐘一次。
- They respond quickly to topology changes: Link-state protocols establish neighbor relationships with the adjacent routers. The failure of a neighbor is detected quickly, and this failure is communicated by using triggered updates to all routers in the network. This immediate reporting generally leads to fast convergence times.能快速回應拓樸變化：鏈路狀態協定會與相鄰路由器建立鄰居關係。鄰居故障能被迅速偵測到，並透過觸發式更新傳達給網路中所有路由器。這種即時回報通常能帶來快速的收斂時間。
- More information is communicated between routers: Routers that run a link-state protocol have a common view on the network. Each router has full information about other routers and links between them, including the metric on each link.路由器之間交換的資訊更多：執行鏈路狀態協定的路由器對網路有共同的視角。每台路由器都擁有其他路由器及彼此之間鏈路的完整資訊，包括每條鏈路的度量值。