官术网_书友最值得收藏!

Routers

Figure 4: A Cisco Router; source: www.cisco.com

A router is a device that works at layer 3 of the OSI model, and hence routes IP packets between different subnets. The hardware architecture at a block level would be similar to that of a switch, with the difference that the switch processor is replaced by a route processor. Since the router operates at a higher OSI layer than that of a switch, all the functions of a layer 2 switch would also be inbuilt into the router.

The route processor is the brain of the router. The routing tables are built by the route processor by running various routing protocols that we will discuss in the next chapter. These routing tables can then be sent to specific ASICs controlling the different ports on a router for faster processing.

A router may have one or more Ethernet ports that connect to different LAN segments, one or more WAN ports that can connect to the WAN links over serial interfaces such as an E1 interface providing 2 Mbps bandwidth, or even ATM interfaces that can connect to legacy ATM backbones. The router will also have the console port and optional AUX ports for connecting to the device for configuration.

Like switches, routers also come in multiple form factors and could be modular or fixed configuration devices. Some of the commonly used routers in the Cisco family are the Integrated Services Routers (ISR) 3k & ISR4k series, or the highend ASR 9k series of routers. All of these routers would run a variant of the IOS software that implements the different features within the router, including the different routing protocols. IOS is the most common software, while IOS-XE is a modular build of the IOS software. IOS-XR is a modular software that runs on highend routers.

主站蜘蛛池模板: 盐源县| 象山县| 福泉市| 台南县| 陆河县| 长春市| 隆尧县| 安新县| 石阡县| 香河县| 台东市| 城市| 灵山县| 许昌县| 清远市| 运城市| 华亭县| 北安市| 广河县| 琼海市| 万州区| 南通市| 寿阳县| 石景山区| 喜德县| 仁布县| 留坝县| 郎溪县| 安西县| 闽清县| 墨脱县| 神木县| 剑河县| 津市市| 个旧市| 双桥区| 绥棱县| 江津市| 尉氏县| 临汾市| 临沧市|