Application viewpoint: comprehensive application of HSRP Routing Protocol in Campus

Currently, HSRP routing protocols are widely used. So I have studied the application of HSRP routing protocols on campus. I would like to share this with you and hope it will be useful to you. With the increasing popularity of the Internet, people are increasingly dependent on the network. At the same time, this puts forward higher requirements on Network stability. People naturally think of a device-based backup structure, just like using a dual hard disk structure on servers to improve data security.

Vro is the core and heart of the entire network. If a fatal fault occurs on the vro, it will paralyze the local network. If it is a backbone router, the impact scope will be greater, the loss is hard to estimate. Therefore, using hot backup for routers is an inevitable choice to improve the network robustness (robust. When a router is completely unable to work, all its functions will be taken over by another backup router in the system until the faulty router returns to normal, this is the problem to be solved by Cisco's hot wait routing protocol (HotStandbyRouterProtocal, HSRP routing protocol.

I. Overview of HSRP Routing Protocol

The condition for implementing the HSRP routing protocol is that there are multiple routers in the system and they form a "hot wait group", which forms a virtual router. At any time, only one vro in A group is active and forwards data packets. If the active vro fails, a waiting vro is selected to replace the active vro, however, in the view of hosts in the network, the virtual router has not changed. As a result, the host still maintains the connection and is not affected by the fault, which effectively solves the problem of router switching. To reduce the data traffic of the network, after setting the active router and waiting for the router, only the active router and the waiting router regularly send the HSRP route protocol packets. If the active router fails, wait until the router takes over as the active router. If a vro fails or becomes an active vro, the other vro is selected as the waiting vro.

In a Specific Lan, multiple hot wait groups may coexist or overlap. Each hot wait group imitates a virtual router, which has a Well-known-MAC address and an IP address. The IP address, the interface address of the vro in the group, and the host are in the same subnet, but cannot be the same. When multiple hot wait groups exist on a LAN, distributing hosts to different hot wait groups can share the load.

Ii. HSRP Route Protocol packet format

In a hot wait group, vrouters regularly broadcast status information based on different types of data packets. The protocol runs on UDP. The port number is 1985, the destination address is 224.0.0.2, And the TTL value is 1. The source address of the packet is the actual IP address of the sender router, rather than the virtual address. This can be used to mark different routers. The UDP format 1 is shown in.

Iii. vro status and status TRANSITION IN HSRP

In a hot wait group, each vro runs a simple state machine, which is switched to a different state by triggering the current state and event. These include the following statuses.

1. The initial status of the HSRP route protocol when it is started. The HSRP route protocol is not running yet. Generally, this status is entered when the configuration is changed or the port is just started.

2. In this status, the vro does not determine the virtual IP address, nor does it see the authenticated HELLO packets from the active vro. The router is still waiting for the HELLO message sent from the active router.

3. The vro In the listener status has obtained a virtual IP address, but it is neither an active router nor a waiting router. It monitors the HELLO messages sent from the active router and waiting for the router.

4. In this status, the vro regularly sends HELLO messages and actively participates in the active vro or waits for the election of the vro.

5. A waiting vro in this status is the next candidate active vro, which regularly sends HELLO messages.

6. A vro in the active state is responsible for packet forwarding. These packets are sent to the virtual MAC address of the group. It regularly sends HELLO messages. In addition, each vro has three timers, namely, the active timer, the waiting timer, and the call timer. status changes are caused by events, different events act on different states, and different actions are generated, such as starting a timer and sending a message.

IV. Implementation of HSRP Routing Protocol in Campus Network

The Campus Network of East China Normal University is relatively large, and there are many hosts accessing the internet. There are 16 class C addresses in total. To ensure data security and broadcast storms and improve network performance, the campus network is divided into 60 subnets. In the network center, Cisco's ipvst5509 is used as the center switch, with RSM as the router between VLANs, and a Cisco7000 series router and RSM are used. Both support VLAN and HSRP routing protocol on VLAN. There is an HSRP routing protocol group in each virtual LAN. Logically, the RSM of Cisco7010 and Cisco5509 has LAN interfaces and IP addresses in each virtual LAN, configure a virtual address as the gateway of all hosts in the virtual LAN.