使用的方法是采用DHCP方式为用户分配IP，然后限定这些用户只能使用动态IP的方式，如果改成静态IP的方式则不能连接上网络；也就是使用了DHCP SNOOPING功能。 例子： version 12.1 no service pad service timestamps debug uptime service timestamps log uptime no service p assword-encryption service compress-config ! hostname C4-2_4506 ! enable password xxxxxxx! clock timezone GMT 8 ip subnet-zero no ip domain-lookup ! ip dhcp snooping vlan 180-181 // 对哪些VLAN 进行限制 ip dhcp snooping ip arp inspection vlan 180-181 ip arp inspection validate src-mac dst-mac ip errdisable recovery cause udld errdisable recovery cause bpduguard errdisable recovery cause security-violation errdisable recovery cause channel-misconfig errdisable recovery cause pagp-flap errdisable recovery cause dtp-flap errdisable recovery cause link-flap errdisable recovery cause l2ptguard errdisable recovery cause psecure-violation errdisable recovery cause gbic-invalid errdisable recovery cause dhcp-rate-limit errdisable recovery cause unicast-flood errdisable recovery cause vmps errdisable recovery cause arp-inspection errdisable recovery interval 30 spanning-tree extend system-id ! ! interface GigabitEthernet2/1 // 对该端口接入的用户进行限制，可以下联交换机 ip arp inspection limit rate 100 arp timeout 2 ip dhcp snooping limit rate 100 ! interface GigabitEthernet2/2 ip arp inspection limit rate 100 arp timeout 2 ip dhcp snooping limit rate 100 ! interface GigabitEthernet2/3 ip arp inspection limit rate 100 arp timeout 2 ip dhcp snooping limit rate 100 ! interface GigabitEthernet2/4 ip arp inspection limit rate 100 arp timeout 2 ip dhcp snooping limit rate 100 --More-- 编者注：对不需要明确地址的所有人的时候是一个很好的解决办法。另外，可以查看[url]www.cisco.com[/url]的 IP Source Guard Similar to DHCP snooping, this feature is enabled on a DHCP snooping untrusted Layer 2 port. Initially, all IP traffic on the port is blocked except for DHCP packets that are captured by the DHCP snooping process. When a client receives a valid IP address from the DHCP server, or when a static IP source binding is configured by the user, a per-port and VLAN Access Control List (PACL) is installed on the port. This process restricts the client IP traffic to those source IP addresses configured in the binding; any IP traffic with a source IP address other than that in the IP source binding will be filtered out. This filtering limits a host's ability to attack the network by claiming neighbor host's IP address.
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