Ip dhcp snooping information option – Brocade 6910 Ethernet Access Switch Configuration Guide (Supporting R2.2.0.0) User Manual
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Brocade 6910 Ethernet Access Switch Configuration Guide
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DHCP Snooping
•
If a DHCP packet from a client passes the filtering criteria above, it will only be forwarded
to trusted ports in the same VLAN.
•
If a DHCP packet is from server is received on a trusted port, it will be forwarded to both
trusted and untrusted ports in the same VLAN.
•
If the DHCP snooping is globally disabled, all dynamic bindings are removed from the binding
table.
•
Additional considerations when the switch itself is a DHCP client – The port(s) through which
the switch submits a client request to the DHCP server must be configured as trusted (using
the
command). Note that the switch will not add a dynamic entry for
itself to the binding table when it receives an ACK message from a DHCP server. Also, when the
switch sends out DHCP client packets for itself, no filtering takes place. However, when the
switch receives any messages from a DHCP server, any packets received from untrusted ports
are dropped.
Example
This example enables DHCP snooping globally for the switch.
Console(config)#ip dhcp snooping
Console(config)#
Related Commands
ip dhcp snooping information option
This command enables the use of DHCP Option 82 information for the switch, and specifies the
frame format to use for the remote-id when Option 82 information is generated by the switch. Use
the no form without any keywords to disable this function, the no form with the encode no-subtype
keyword to enable use of sub-type and sub-length in CID/RID fields, or the no form with the
remote-id keyword to set the remote ID to the switch’s MAC address encoded in hexadecimal.
Syntax
ip dhcp snooping information option
[encode no-subtype] [remote-id {ip-address [encode {ascii | hex}] |
mac-address [encode {ascii | hex}] | string string}]
no ip dhcp snooping information option [encode no-subtype]
[remote-id [ip-address encode] | [mac-address encode]]
encode no-subtype - Disables use of sub-type and sub-length fields in circuit-ID (CID) and
remote-ID (RID) in Option 82 information.
mac-address - Inserts a MAC address in the remote ID sub-option for the DHCP snooping
agent (that is, the MAC address of the switch’s CPU).
ip-address - Inserts an IP address in the remote ID sub-option for the DHCP snooping
agent (that is, the IP address of the management interface).
encode - Indicates encoding in ASCII or hexadecimal.
string - An arbitrary string inserted into the remote identifier field. (Range: 1-32 characters)