cisco 2600 的限速迷惑

cisco, 限速

Using 1359 out of 29688 bytes
!
version 12.2
service timestamps debug uptime
service timestamps log uptime
no service password-encryption
!
hostname 2600
!
enable secret 5 xxxxxxxxx
!
ip subnet-zero
!
!
no ip domain-lookup
!
!
!
!
interface Loopback0
ip address 192.168.100.100 255.255.255.0
!
interface Loopback1
ip address 192.168.101.1 255.255.255.0
!
interface FastEthernet0/0
ip address 218.249.x.x 255.255.255.224
no keepalive
duplex auto
speed auto
!
interface Serial0/0
no ip address
encapsulation ppp
no fair-queue
!
interface FastEthernet0/1
ip address 218.249.x.y 255.255.255.224
duplex auto
speed auto!
interface Serial0/1
no ip address
encapsulation ppp
no fair-queue
!
interface Ethernet1/0
ip address 192.168.168.218 255.255.255.252
rate-limit input access-group 101 2280000 20000 30000 conform-action transmit exceed-action drop
rate-limit output access-group 101 2160000 20000 30000 conform-action transmit exceed-action drop
half-duplex!
ip classless
ip route 0.0.0.0 0.0.0.0 192.168.168.217
ip http server
ip pim bidir-enable
!
!
logging trap debugging
logging facility syslog
logging 172.18.0.103
access-list 1 permit any
access-list 101 permit ip 218.249.x.x 0.0.0.31 any
!
line con 0
exec-timeout 0 0
login
line aux 0
line vty 0 4
password asdfasdf
login
!
!
end

上面有三个部分用红色标出，我有以下两个疑问
1、为什么设置了 2 个 FE 都有公网地址？而且确实两个都可以 ping 通
2、这个 rate-limit 的意思是什么，他要实现的目的是什么？为什么是办双工？

网友：

1 是否是公网地址这个问题是相对的.路邮的时候只要是有相应的路邮可以到达他就可以了. 如果是一个骨干上面的路由器连接两个公网用的这样的配置也有.当然了路由协议就复杂一些了.
2 http://www.cisco.com/en/US/produ ... 6f22.html#wp1057318
自己看看吧.很简单.