哪位能说说ip route 0.0.0.0 0.0.0.0和ip default-network命令的区别吗？
我所知道的ip route 命令会向路由表里加一条静态路由，ip default-network命令不会
ip route 命令按接口和地址指定缺省路由ip default-network命令按网络指定
谁能说说还有什么区别？以及在什么情况下使用哪条吗？还有他们在再发布时的区别！
FW:发信人: canway()
整理人: sanjose(2000-09-26 10:54:44), 站内信件
Q:
听了各位解释，有些明白，可是路由器没有路由还叫路由器吗，那样两个命令
功能似乎是一样的，都是把不知道到的包发给下一个站点，可是我在做一个项目
时，
设置ip default-gateway就不行。用ip route 0.0.0.0 0.0.0.0 xxxxxxxx
就通了。 是不是这样，对于ip default-gateway来说，只有对这个网段才有效，
而从其他
网段路由过来的其他网段的信息到了用ip default-gateway的网段就不能利用这
个 命令传送，而是要用ip route 0.0.0.0 0.0.0.0.了。也就是ip route 0.0.0
.0
0.0.0.0才能完成路由功能，不知道理解的对吗
Answer:
1。 ip default-gateway用与路由器不作路由时使用，这时路由器就只是一台主
机好象Win95PC一样需要配一个网关才能与外界通信。
假如 “no ip routing"则路由器就不作路由。这时你可以配bridge-group，把路
由表及里器当switch使。
2。 ip route 0.0.0.0 0.0.0.0 用于履行路由功能。假如ip routin
g是enable的则ip default-gateway不起作用.
FW:区别在于，ip route本机生效，ip default-network可以影响整个路由协议域
http://www.cisco.com/en/US/customer...sHtml#ipnetwork
FW:IntrodUCtion
This Tech Note eXPlains how to configure a default route, or gateway of last resort, using the following IP commands: ip default-gateway, ip default-network, and ip route 0.0.0.0 0.0.0.0. Let's look at each of these commands in more detail.
Before You Begin
Conventions
For more information on document conventions, see the Cisco Technical Tips Conventions.
Prerequisites
There are no specific prerequisites for this document.
Components Used
This document is not restricted to specific software and hardware versions.
The information presented in this document was created from devices in a specific lab environment. All of the devices used in this document started with a cleared (default) configuration. If you are working in a live network, ensure that you understand the potential impact of any command before using it.
ip default-gateway
The ip default-gateway command differs from the other two commands in that it should only be used when ip routing is disabled on the Cisco router.
For instance, if the router is a host in the IP world, you can use this command to define a default gateway for it. You might also use this command when your low end Cisco router is in boot mode in order to TFTP a Cisco IOS® Software image to the router. In boot mode, the router doesn't have ip routing enabled.
ip default-network
Unlike the ip default-gateway command, you can use ip default-network when ip routing is enabled on the Cisco router. When you configure ip default-network the router considers routes to that network for installation as the gateway of last resort on the router.
For every network configured with ip default-network, if a router has a route to that network, that route is flagged as a candidate default route. Let's look at the following routing table taken from a Cisco router:
2513#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
Gateway of last resort is not set
161.44.0.0 255.255.255.0 is subnetted, 1 subnets
C 161.44.192.0 is directly connected, Ethernet0
S 198.10.1.0 [1/0] via 161.44.192.2
131.108.0.0 255.255.255.0 is subnetted, 1 subnets
C 131.108.99.0 is directly connected, TokenRing0
Note the static route to 198.10.1.0 via 161.44.192.2 and that the gateway of last resort isn't set. If we configure ip default-network 198.10.1.0, the routing table changes to the following:
2513#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
Gateway of last resort is 161.44.192.2 to network 198.10.1.0
161.44.0.0 255.255.255.0 is subnetted, 1 subnets
C 161.44.192.0 is directly connected, Ethernet0
S 161.44.0.0 255.255.0.0 [1/0] via 161.44.192.0
S* 198.10.1.0 [1/0] via 161.44.192.2
131.108.0.0 255.255.255.0 is subnetted, 1 subnets
C 131.108.99.0 is directly connected, TokenRing0
2513#show ip protocols
2513#
We can see the gateway of last resort has now been set as 161.44.192.2. This result is independent of any routing protocol, as shown by the show ip protocols command at the bottom of the output.
We can add another candidate default route simply by configuring another instance of ip default-network:
2513#config terminal
Enter configuration commands, one per line. End with CNTL/Z.
2513(config)#ip route 171.70.24.0 255.255.255.0 131.108.99.2
2513(config)#ip default-network 171.70.24.0
2513(config)#^Z
2513#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
Gateway of last resort is 161.44.192.2 to network 198.10.1.0
161.44.0.0 255.255.255.0 is subnetted, 1 subnets
C 161.44.192.0 is directly connected, Ethernet0
S 161.44.0.0 255.255.0.0 [1/0] via 161.44.192.0
S* 198.10.1.0 [1/0] via 161.44.192.2
171.70.0.0 is variably subnetted, 2 subnets, 2 masks
S 171.70.0.0 255.255.0.0 [1/0] via 171.70.24.0
S 171.70.24.0 255.255.255.0 [1/0] via 131.108.99.2
131.108.0.0 255.255.255.0 is subnetted, 1 subnets
C 131.108.99.0 is directly connected, TokenRing0
Flagging a Default Network
Note: The ip default-network command is classful, which means if the router has a route to the subnet indicated by this command, it installs the route to the major net. At this point neither network has been flagged as the default network. The ip default-network command must be issued again, using the major net, in order to flag the candidate default route.
2513#config terminal
Enter configuration commands, one per line. End with CNTL/Z.
2513(config)#ip default-network 171.70.0.0
2513(config)#^Z
2513#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
Gateway of last resort is 161.44.192.2 to network 198.10.1.0
161.44.0.0 255.255.255.0 is subnetted, 1 subnets
C 161.44.192.0 is directly connected, Ethernet0
S 161.44.0.0 255.255.0.0 [1/0] via 161.44.192.0
S* 198.10.1.0 [1/0] via 161.44.192.2
171.70.0.0 is variab
