To forward data, routers must first configure routing data, usually static routes or dynamic routes can be set up according to the size of the network. Static routing is easy to configure, low system requirements, and is suitable for small networks with simple and stable topology. The disadvantage is that it cannot automatically adapt to changes in network topology and requires manual intervention. The dynamic routing protocol has its own routing algorithm that can automatically adapt to changes in network topology and is suitable for networks with a certain number of Layer 3 devices. The disadvantage is that the configuration requires higher user requirements, higher requirements for the system than static routing, and will occupy a certain amount of network resources. Common dynamic routing protocols include RIP, OSPF, IS-IS, IGRP, EIGRP, BGP, etc.
Internal gateway protocol: RIP, OSPF, IS-IS, IGRP, EIGRP is an internal gateway protocol (IGP), which is suitable for the operation of a unified routing protocol for a single ISP.
External gateway protocolBGP is a routing protocol between autonomous systems, which is an external gateway protocol that is mostly used on the INTERNET to exchange routing information between different operators.
RIP routing protocol
RIP is short for Routing Information Protocol. It is a relatively simple internal gateway protocol IGP (Interior Gateway Protocol), which is mainly used in smaller networks, such as campus networks and regional networks with a simpler structure. RIPs are generally not used for more complex environments and large networks.
RIP is a protocol based on the Distance-Vector algorithm, which exchanges routing information through UDP packets and uses a port number of 520.
RIP uses hop count to measure the distance to a destination address, called a measure. In RIP, by default, the number of hops from the router to the network directly connected to it is 0, the number of hops for the network reachable through a router is 1, and so on. That is, the measure is equal to the number of routers from this network to the destination network. In order to limit the convergence time, RIP stipulates that the metric value should be an integer between 0~15, and the number of hops greater than or equal to 16 is defined as infinity, that is, the destination network or host is unreachable. This limitation makes RIP impossible to use in large networks.
To improve performance and prevent routing loops, RIP supports Split Horizon and Poison Reverse functions.
Because RIP is relatively simple to implement, and it is much easier to configure and manage than OSPF and IS-IS, it is still widely used in actual networking.
RIP is available in two versions: RIP V1 and RIP V2.
1. RIP V1 is a classful routing protocol, which only supports publishing protocol packets in broadcast mode. RIP-1 does not carry mask information in its protocol packets, and it can only recognize routes from natural CIDR blocks such as A, B, and C, so RIP-1 cannot support route aggregation or discontiguous subnets.
2. RIP V2 is a classless routing protocol, which has the following advantages compared with RIP-1:
1) Support external route tags (Route Tag), which can flexibly control the route according to the tag in the routing policy.
2) The packet carries mask information and supports route aggregation and CIDR (Classless Inter-Domain Routing).
3) Support to specify the next hop, and you can choose the optimal next hop address on the broadcast network.
4) Support multicast to send update packets, and only the RIP-2 router can receive protocol packets to reduce resource consumption.
5) Supports verification of protocol packets, and provides two methods: plaintext verification and MD5 verification to enhance security.
OSPF routing protocol
OSPF (Open Shortest Path First) is an internal gateway protocol based on link state developed by the IETF organization. Currently, OSPF Version 2 (RFC2328) is used for IPv4 protocols; OSPF Version 3 (RFC2740) is used for IPv6 protocols.
OSPF is currently the most widely used IGP protocol。 The design idea of OSPF is to provide a hierarchical and zonal routing protocol for large and medium-sized networks. Its algorithm is complex, but it can guarantee no intra-domain loop.
OSPF features the following:
1. Wide range of adaptability: supports large-scale networks, up to hundreds of routers.
2. Support masks: Because OSPF packets carry mask information, the OSPF protocol is not limited by natural masks and provides good support for VLSM.
3. Fast convergence: Send update packets immediately after the topology of the network changes, so that this change is synchronized in the autonomous system.
4. No self-loop: Since OSPF uses the shortest path tree algorithm to calculate the route according to the collected link state, it is guaranteed that no self-loop route will be generated from the algorithm itself.
5. Regional division: The network of the autonomous system is allowed to be divided into regions for management, and the routing information transmitted between regions is further abstracted, thereby reducing the network bandwidth occupied.
6. Equivalent routing: Support multiple equivalent routes to the same destination address.
7. Route classification: 4 different types of routes are used, in order of priority: intra-regional routes, inter-regional routes, the first type of external routes, and the second type of external routes.
8. Support validation: Support region and interface-based packet verification to ensure the security of packet interaction.
9. Multicast transmission: Send protocol packets with multicast addresses on certain types of links to reduce interference with other devices.
IS-IS routing protocol
IS-IS (Intermediate System-to-Intermediate System) was originally developed by the International Organization for Standardization (ISO) for its connectionless network protocol CLNP (ConnectionLess Network). Protocol).
In order to provide routing support for IP, the IETF has expanded and modified IS-IS in RFC1195 to enable it to be used in both TCP/IP and OSI environments, known as Integrated IS-IS (Integrated IS-IS or Dual IS-IS).
IS-IS is an internal gateway protocol (IGP) used inside an autonomous system. IS-IS is a link-state protocol that uses the Shortest Path First (SPF) algorithm for routing calculations, which has many similarities with the OSPF protocol.From the perspective of global deployment, OSPF is still used in the majority, while IS-IS has begun to be used more in recent years。
IGRP routing protocol
IGRP protocol is the abbreviation of "Interior Gateway Routing Protool", which was independently developed by Cisco in the 80s of the twentieth century and belongs to Cisco's private protocol. IGRP, like RIP, belongs to the same distance vector routing protocol, so it has similarities in many aspects, such as IGRP is also a periodic broadcast routing table, and there is also a maximum number of hops (the default is 100 hops, and if it reaches or exceeds 100 hops, the target network is considered unreachable). The biggest feature of IGRP is that it uses mixed metrics, which take into account the five aspects of link bandwidth, latency, load, MTU, and reliability to calculate the route metrics, unlike other IGP protocols that simply consider one aspect to calculate the metrics. At present, IGRP has been replaced by Cisco's independently developed EIGRP protocol, and Cisco IOS (Internetwork Operating System) with version number 12.3 and above no longer supports this protocol, and there are few networks running IGRP protocol.
EIGRP routing protocol
EIGRP Due to the various shortcomings and shortcomings of the IGRP protocol, Cisco developed the EIGRP protocol (Enhanced Internal Gateway Routing Protocol) to replace the IGRP protocol. EIGRP is an advanced distance vector routing protocol (also known as a hybrid routing protocol), which inherits the mixed measurement of IGRP, and its biggest feature is the introduction of non-equivalent load balancing technology and extremely fast convergence speed. The EIGRP protocol is widely deployed in Cisco device network environments.
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The hyperlink login is visible.
The hyperlink login is visible.
The hyperlink login is visible. |
Posted on 2025-12-1 10:00:20
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