Brief description of Dynamic Routing Protocol

The dynamic routing protocol is described in detail in this article. First, let's take a look at the usage and environment requirements of the dynamic routing protocol. In a network without other routers, it is meaningless to route the Broadcast Communication outbound from the network interface. For your network bandwidth and vro resource usage, the efficiency is very low. Let's take a look at how to use the passive-interface command to better control the bandwidth ｡

To correctly configure the dynamic routing protocol, the passive-interface command is not unknown. However, if you are not using dynamic routing protocols (such as OSPF, OSPF, or RIP, you cannot use this command. The passive-interface command only works in the Router Configuration Mode. When you see the command line prompt shown below, then you will know that you have entered this mode: Router (config-router )#, you can use the passive-interface command to notify the dynamic routing protocol not to send network broadcasts through this interface. This command can take effect for all IP dynamic routing protocols, except for BGP only ｡

However, this command works on OSPF, which IS a little different from IS-IS. ospf is used to passively specify the network interface as stub, does not send or receive any route updates. When RIP, IGRP, or OSPF is used, it does not send any route, but it can receive them. Similarly, it also sends broadcasts to all non-passive interfaces on the network ｡

There are two ways to use the passive-interface command. Specify an interface as the passive mode, this means that it will not send route updates. First, set all interfaces to passive mode. Then, on the interfaces you plan to send route updates, use the no passive-interface command. Let's take a look at each of the two methods. Note: in both cases, it is assumed that you have already added a network (using network commands) That is a passive interface to the dynamic routing protocol, you only need to specify the interface. Here is an example: Router (config) # router rip Router (config-router) # passive-interface Ethernet 0/0 ｡

To set all interfaces as passive and open an interface separately, you only need to use the passive-interface default and no passive-interface commands (introduced in IOS 12.0). The following is an example: router (config) # router rip Router (config-router) # passive-interface default Router (config-router) # no passive-interface Serial 0/0. Let's look at a simple network, it is used to demonstrate the deep application of this command. Suppose you have two routers connected through a T1 loop, and all routers run RIP. each vro connects to a LAN and the computer connects to the LAN through the ethernet card. You need each vro to know the network of the other vro, right? This is why the dynamic routing protocol is used. However, on the LAN, there are no other routers that can exchange route updates between the two routers ｡

In this case, why do you want to broadcast a route update on the LAN interface every 30 seconds? The answer is you don't want to. This is a waste of LAN bandwidth and computer CPU time. If it is just a small update, it does not cause any problems, but if you can avoid it, why do we need to send such unnecessary communication? So how can we eliminate such unnecessary communication? On each vro, enter the RIP Configuration mode and use the passive-interface command to stop sending route updates on the LAN port. The following is an example: Router (config) # router RIP Router (config-router) # passive-interface Ethernet 0/0. Assume that you have configured the network to be broadcast by using the network command in advance. The following is an example:

Router (config-router) # network 1.0.0 ...... 0 (the Serial network)

Router (config-router) # network 2.0.0.0 (the Ethernet network)

Remember, this means that the system will broadcast the two networks you set by connecting to the serial interface of another vro, this does not prevent your router from receiving route updates from the local network interface (using RIP). If another router is also on the local network and sends updates to your router, it can still receive these updates ｡