ip default-network和ip route 0.0.0.0 0.0.0.0默认路由的区别.doc

ip default-network和ip route 默认路由的区别在自己的2501上研究这三种默认路由的区别.指定默认路由（last resort gateway）的指令供有3种，可以分成两类：1、ip default-gateway当路由器上的ip routing无效时，使用它指定默认路由，用于RXBoot模式（no ip routing）下安装IOS等。或者关闭ip routing 让路由器当主机用,此时需要配置默认网关2、ipdefault-network和ip route 两者都用于ip routing有效的路由器上，区别主要在于路由协议是否传播这条路由信息。比如：IGRP无法识别，因此传播默认路由时必须用ip default-network。当用ip default-network指令设定多条默认路由时，administrative distance最短的成为最终的默认路由；如果有复数条路由distance值相等，那么在路由表（show ip route）中靠上的成为默认路由。同时使用ip default-network和ip route 双方设定默认路由时，如果ip default-network设定的网络是直连（静态、且已知）的，那么它就成为默认路由；如果ip default-network指定的网络是由交换路由信息得来的，则ip route 指定的表项成为默认路由。最后，如果使用多条ip route 指令，则流量会自动在多条链路上负载均衡。官方详细文档点这里 例子:关闭ip routing 举例:mycisco(config)#no ip routing mycisco(config)#ip default-gateway mycisco(config)#endmycisco#ping Type escape sequence to abort.Sending 5, 100-byte ICMP Echoes to 5, timeout is 2 seconds:!Success rate is 100 percent (5/5), round-trip min/avg/max = 60/60/60 msmycisco#show ip routeDefault gateway is Host Gateway Last Use Total Uses InterfaceICMP redirect cache is emptymycisco#ip route例子:ip route mycisco#ping Type escape sequence to abort.Sending 5, 100-byte ICMP Echoes to 5, timeout is 2 seconds:!Success rate is 100 percent (5/5), round-trip min/avg/max = 56/56/60 msmycisco#show ip routeCodes: C - connected, S - static, I - IGRP, R - RIP, M - mobile, B - BGPD - EIGRP, EX - EIGRP external, O - OSPF, IA - OSPF inter area E1 - OSPF external type 1, E2 - OSPF external type 2, E - EGPi - IS-IS, L1 - IS-IS level-1, L2 - IS-IS level-2, * - candidate defaultU - per-user static routeGateway of last resort is to network C /8 is directly connected, Loopback0C /24 is directly connected, Ethernet0S* /0 1/0 via mycisco# ip default-network 必须是在所到网络已经存在路由的情况下,否则执行无效.mycisco(config)#ip route mycisco#show ip routeCodes: C - connected, S - static, I - IGRP, R - RIP, M - mobile, B - BGPD - EIGRP, EX - EIGRP external, O - OSPF, IA - OSPF inter area E1 - OSPF external type 1, E2 - OSPF external type 2, E - EGPi - IS-IS, L1 - IS-IS level-1, L2 - IS-IS level-2, * - candidate defaultU - per-user static routeGateway of last resort is not setC /8 is directly connected, Loopback0S /8 1/0 via C /24 is directly connected, Ethernet0接着我们执行:mycisco(config)#ip default-network 再看路由表:mycisco#show ip routeCodes: C - connected, S - static, I - IGRP, R - RIP, M - mobile, B - BGPD - EIGRP, EX - EIGRP external, O - OSPF, IA - OSPF inter area E1 - OSPF external type 1, E2 - OSPF external type 2, E - EGPi - IS-IS, L1 - IS-IS level-1, L2 - IS-IS level-2, * - candidate defaultU - per-user static routeGateway of last resort is 192.1