Configuring Dhcp Snooping - 3Com E4500-24 Cli Configuration Manual

client cannot be recorded in the DHCP-snooping table. Consequently, this client cannot pass the IP
filtering of the DHCP-snooping table, thus it cannot access external networks.
To solve this problem, the switch supports the configuration of static binding table entries, that is, the
binding relationship between IP address, MAC address, and the port connecting to the client, so that
packets of the client can be correctly forwarded.
IP-to-MAC mappings of authenticated 802.1x clients
If most clients are assigned with static IP addresses, you need to configure an IP static binding for each
client. The configuration is a heavy workload and causes errors easily.
To ensure security, in actual networks, clients are usually connected to networks through 802.1x
authentication. With the authenticated 802.1x client-based IP filtering function enabled, the switch can
record and query the IP-to-MAC mappings of authenticated 802.1x clients to defend against IP attacks.
IP filtering
IP filtering can be implemented based on the DHCP-snooping table, IP static binding table, or
IP-to-MAC mappings of authenticated 802.1x clients, according to actual network requirements. The
switch can filter IP packets in the following modes:
Filtering packets based on their source IP addresses. If the source IP address in a packet and the
number of the port that receives the packet match an entry or mapping, the switch regards the
packet as a valid packet and forwards it; otherwise, the switch drops it directly.
Filtering packets based on their source IP and MAC addresses. If the source IP address and
source MAC address in the packet, and the number of the port that receives the packet match an
entry or mapping, the switch regards the packet as a valid packet and forwards it; otherwise, the
switch drops it directly.

Configuring DHCP Snooping

Configuring DHCP Snooping
Follow these steps to configure DHCP snooping:
To do...
Enter system view
Enable DHCP snooping
Enter Ethernet port view
Specify the current port as a
trusted port
Use the command...
system-view
dhcp-snooping
interface interface-type
interface-number
dhcp-snooping trust
4-5
Remarks
—
Required
By default, the DHCP snooping
function is disabled.
—
Required
By default, after DHCP
snooping is enabled, all ports of
a switch are untrusted ports.