IS-IS 网络设计方案

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　　关于IS-IS 的历史
　　
　　IS-IS was ad hoc in its evolution, whereas OSPF was more formal:
　　
　　1985: Originally called DECnet Phase V Routing
　　
　　1988: Adopted by ISO and renamed IS-IS
　　

　　1990: Publication of RFC 1142, "OSI IS-IS Intradomain Routing Protocol"
　　
　　1990: Publication of RFC 1195, "Use of OSI IS-IS for Routing in TCP/IP and Dual Environments"
　　
　　1991: Cisco IOS Software starts supporting IS-IS
　　
　　1995: ISPs start adopting IS-IS
　　
　　2000: Publication of IETF draft "IS-IS Extensions for Traffic Engineering"
　　
　　2001: Publication of IETF draft "IS-IS Extensions in Support of Generalized MPLS"
　　
　　
　　谁来使用IS-IS
　　IS-IS主要是电信运营商和大型ISP所普遍采用的一种路由协议。ISP在IGP协议中大量采用IS-IS或者OSPF协议，至于这两种协议哪种更有优势，只能说每个网络工程师都有自己所长，有些习惯使用OSPF，有些就善于组建IS-IS的网络。
　　
　　面向对象连接和非面向对象连接
　　面向对象连接就是在数据通过前首先要建立连接，而非面向对象连接则可以不需要建立连接直接发送数据
　　
　　CLNS
　　Connectionless Network Service (CLNS)—CLNS performs datagram transport and does not require a circuit to be established before data is transmitted.
　　
　　IS-IS
　　Variable-length subnet masks (VLSMs). The mask and the prefix are sent in the routing updates.
　　
　　Redistribution of IP routes into and out of IS-IS.
　　
　　Summarization of IP routes.
　　
　　Level 1 ISs are responsible for routing to ESs inside an area. This is similar to OSPF internal nonbackbone routers in a totally stubby area.
　　
　　Level 2 ISs route between areas only. This is similar to internal backbone routers in OSPF.
　　
　　Level 1–2 ISs route between areas and the backbone. They participate in the Level 1 intra-area routing and the Level 2 interarea routing. This is the equivalent of Area Border Routers (ABRs) in OSPF.
　　
　　源码:----------------------------------------------------------
　　
　　NSAP Examples
　　The following examples illustrate how an NSAP address is interpreted by IS-IS and ISO-IGRP.
　　
　　The NSAP 49.0001.aaaa.bbbb.cccc.00 consists of the following:
　　
　　For IS-IS:
　　
　　Area = 49.0001
　　
　　System ID = aaaa.bbbb.cccc
　　
　　N-selector = 00
　　
　　For ISO-IGRP:
　　
　　Domain = 49
　　
　　Area = 0001
　　
　　System ID = aaaa.bbbb.cccc
　　
　　N-selector = ignored by ISO-IGRP
　　
　　The NSAP 39.0f01.0002.0000.0c00.1111.00 consists of the following:
　　
　　For IS-IS:
　　
　　Area = 39.0f01.0002
　　
　　System ID = 0000.0c00.1111
　　
　　N-selector = 00
　　
　　For ISO-IGRP:
　　
　　Domain = 39.0f01
　　
　　Area = 0002
　　
　　System ID = 0000.0c00.1111
　　
　　N-selector = ignored by ISO-IGRP
　　
　　--------------------------------------------------------------------------------
　　基本配置
　　hostname R1
　　
　　!
　　interface Serial0
　　ip address 192.168.120.1 255.255.255.0
　　ip router isis
　　!
　　router isis
　　net 49.0001.1921.6800.1005.00
　　
　　is-type level-1
　　
　　!
　　!backbone_r1 EIGRP configuration exercise configuration
　　!
　　! This file is designed to be copied and pasted into a router that already
　　! has the previous BSCN configuration files loaded, at the # prompt
　　!
　　conf t
　　!
　　no router isis
　　no clns routing
　　!
　　access-list 1 permit 172.16.10.0
　　access-list 1 permit 172.16.11.0
　　route-map passext permit 10
　　match ip address 1
　　!
　　router eigrp 200
　　redistribute connected metric 10000 100 255 1 1500 route-map passext
　　network 10.0.0.0
　　!

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