DGS-3000 Series Layer 2 Managed Gigabit Ethernet Switch CLI Reference Guide
424
Restrictions
None.
Example
To show IMPB entries:
GS-3000-26TC:admin#show address_binding ip_mac all
Command: show address_binding ip_mac all
M(Mode) - D:DHCP, N:ND S:Static ACL - A:Active I:Inactive
IP Address MAC Address M ACL Ports
--------------------------------------- ----------------- -- --- -------------
10.1.1.1 00-00-00-00-00-11 S I 1-26
FE80::240:5FF:FE00:28 00-00-00-00-00-11 S I 1-26
Total Entries : 2
DGS-3000-26TC:admin#
enable address_binding dhcp_snoop
39-11
Description
This command is used to enable DHCP snooping mode.
By default, DHCP snooping is disabled.
If a user enables DHCP Snooping mode, all ports which have IMPB disabled will become server
ports. The switch will learn the IP addresses through server ports (by using DHCP Offer and
DHCP ACK packets).
Note that the DHCP discover packet cannot be passed thru the user ports if the allow_zeroip
function is disabled on the port.
The auto-learned IMPB entry will be mapped to a specific source port based on the MAC address
learning function. This entry will be created as an IP-Inspection mode binding entry for this specific
port. Each entry is associated with a lease time. When the lease time has expires, the expired
entry will be removed from the port. The auto-learned binding entry can be moved from one port to
another port if the DHCP snooping function has learned that the MAC address has moved to a
different port.
If a situation occurs where a binding entry learned by DHCP snooping conflicts with a statically
configured entry. The binding relation has conflicted. For example, if IP A is binded to MAC X with
a static configuration and suppose that the binding entry learned by DHCP snooping is that IP A is
bound to MAC Y, and then it is conflict. When the DHCP snooping learned entry binds with the
static configured entry, and the DHCP snooping learned entry will not be created.
In a situation where the same IMPB pair has been statically configured, the auto-learned entry will
not be created. In a situation where the learned information is consistent with the statically
configured entry the auto-learned entry will not be created. In a situation where the entry is
statically configured in ARP mode the auto learned entry will not be created. In a situation where
the entry is statically configured on one port and the entry is auto-learned on another port, the
auto-learned entry will not be created.
Summary of Contents for DGS-3000 series
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