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

ip default-network和ip route 0.0.0.0 0.0.0.0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、[b]ip default-gateway[/b]
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、[b]ip default-network和ip route 0.0.0.0
0.0.0.0[/b]
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0.0.0.0，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 0.0.0.0 0.0.0.0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 0.0.0.0
0.0.0.0指定的表项成为默认路由。

最后，如果使用多条ip route 0.0.0.0
0.0.0.0指令，则流量会自动在多条链路上负载均衡。

例子:

关闭ip routing 举例:
mycisco(config)#no ip routing
mycisco(config)#ip default-gateway 192.168.0.1

mycisco(config)#end
mycisco#ping www.flashku.com

Type escape sequence to
abort.
Sending 5, 100-byte ICMP Echoes to 61.152.167.75, timeout is 2
seconds:
!!!!!
Success rate is 100 percent (5/5), round-trip min/avg/max = 60/60/60 ms
mycisco#show
ip route
Default gateway is
192.168.0.1
Host Gateway Last Use Total
Uses Interface
ICMP redirect cache is
empty
mycisco#

ip
route例子:
ip route 0.0.0.0 0.0.0.0
192.168.0.1

mycisco#ping www.flashku.com
Type escape sequence to
abort.
Sending 5, 100-byte ICMP Echoes to 61.152.167.75, timeout is 2
seconds:
!!!!!
Success rate is 100 percent (5/5), round-trip min/avg/max = 56/56/60 ms
mycisco#show
ip route
Codes: C - connected, S
- static, I - IGRP, R - RIP, M - mobile, B - BGP
D - EIGRP, EX - EIGRP
external, O - OSPF, IA - OSPF inter area
E1 - OSPF external type 1,
E2 - OSPF external type 2, E - EGP
i - IS-IS, L1 - IS-IS level-1, L2 -
IS-IS level-2, * - candidate default
U - per-user static
route
Gateway of last resort is 192.168.0.1 to network 0.0.0.0
C
1.0.0.0/8 is directly connected, Loopback0
C 192.168.0.0/24 is directly
connected, Ethernet0
S* 0.0.0.0/0 [1/0] via
192.168.0.1
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 61.0.0.0 255.0.0.0
192.168.0.1
mycisco#show ip
route
Codes: C - connected, S - static, I - IGRP, R - RIP, M - mobile, B -
BGP
D - EIGRP, EX - EIGRP external, O - OSPF, IA - OSPF inter area

E1 - OSPF external type 1, E2 - OSPF external type 2, E - EGP

i - IS-IS, L1 - IS-IS level-1, L2 - IS-IS level-2, * - candidate default

U - per-user static route
Gateway of last resort
is not set
C 1.0.0.0/8 is directly connected,
Loopback0
S 61.0.0.0/8 [1/0] via 192.168.0.1
C 192.168.0.0/24 is
directly connected, Ethernet0

接着我们执行:
mycisco(config)#ip default-network
61.0.0.0

再看路由表:
mycisco#show ip route
Codes: C - connected, S - static, I -
IGRP, R - RIP, M - mobile, B - BGP
D - EIGRP, EX - EIGRP external, O -
OSPF, IA - OSPF inter area
E1 - OSPF external type 1, E2 - OSPF
external type 2, E - EGP
i - IS-IS, L1 - IS-IS level-1, L2 - IS-IS
level-2, * - candidate default
U - per-user static
route
Gateway of last resort is 192.168.0.1 to
network 61.0.0.0
C 1.0.0.0/8 is directly connected,
Loopback0
S* 61.0.0.0/8 [1/0] via
192.168.0.1
C 192.168.0.0/24 is directly connected,
Ethernet0