用Route Map实现多ISP Internet接入问题请高手赐教

R2:为公网接入点,为了保证能一天24小时公司的网络能上INTERNET,现接入两家供应商的线路来连接INTERNET,

即然接入了两家供应商线路,当然希望两条线路能同时启用做到负载均衡的目的,当一条线路出了问题,客户端还可以走另一条线路出到INTERNET,现在要在R2路由器上做相关设置以达到我们所需求.以下是在R2上的配置如下:

R2#show run 
Building configuration...

Current configuration : 1449 bytes 
! 
version 12.4 
service timestamps debug datetime msec 
service timestamps log datetime msec 
no service password-encryption 
! 
hostname R2 
! 
boot-start-marker 
boot-end-marker 
! 
no aaa new-model 
memory-size iomem 5 
! 
ip cef 
!

interface Serial0/0 
 ip address 150.17.232.2 255.255.254.0 
 ip nat inside 
 ip virtual-reassembly 
 serial restart-delay 0 
! 
interface Serial0/1 
 ip address 192.168.2.1 255.255.255.0 
 ip nat outside 
 ip virtual-reassembly 
 serial restart-delay 0 
! 
interface Serial0/2 
 ip address 172.16.20.1 255.255.0.0 
 ip nat outside 
 ip virtual-reassembly 
 serial restart-delay 0 
! 
ip http server 
no ip http secure-server 
! 
ip nat inside source route-map isp1 interface Serial0/1 overload 
ip nat inside source route-map isp2 interface Serial0/2 overload 
! 
access-list 100 permit ip 150.17.232.0 0.0.0.255 192.168.2.0 0.0.0.255 
access-list 101 permit ip 150.17.232.0 0.0.0.255 any 
! 
route-map isp2 permit 10 
 match ip address 101 
 match interface Serial0/2 
! 
route-map isp1 permit 10 
 match ip address 100 
 match interface Serial0/1 
! 
control-plane 
! 
line con 0 
 exec-timeout 0 0 
 logging synchronous 
line aux 0 
line vty 0 4 
 login

问:用router-map 与直接用PAT它们之间有什么区别?

是不是用router-map能够自动做负载均衡,而用PAT则只能走一条线路呢?

第一种方法用router-map来配置

ip nat inside source route-map isp1 interface Serial0/1 overload 
ip nat inside source route-map isp2 interface Serial0/2 overload 
! 
access-list 100 permit ip 150.17.232.0 0.0.0.255 192.168.2.0 0.0.0.255 
access-list 101 permit ip 150.17.232.0 0.0.0.255 any 
! 
route-map isp2 permit 10 
 match ip address 101 
 match interface Serial0/2 
! 
route-map isp1 permit 10 
 match ip address 100 
 match interface Serial0/1

第二种方法直接用PAT来做转换配置

ip nat inside source list 100 interface Serial0/1 overload 
ip nat inside source list 101 interface Serial0/2 overload 
! 
access-list 100 permit ip 150.17.232.0 0.0.0.255 192.168.2.0 0.0.0.255 
access-list 101 permit ip 150.17.232.0 0.0.0.255 any 
!

以上两种配置在客户端PING ISP1和ISP2都能通过 
R2#show ip nat translations 
Pro Inside global      Inside local       Outside local      Outside global 
icmp 172.16.20.1:6     150.17.232.1:6     172.16.20.2:6      172.16.20.2:6 
icmp 192.168.2.1:7     150.17.232.1:7     192.168.2.2:7      192.168.2.2:7

     本文转自allanhi 51CTO博客，原文链接：http://blog.51cto.com/allanfan/217602，如需转载请自行联系原作者