C
LIENT
S
ECURITY
C
OMMANDS
22-12
- If DHCP snooping is enabled globally, and also enabled on the
VLAN where the DHCP packet is received, all DHCP packets are
forwarded for a
trusted
port. If the received packet is a DHCP ACK
message, a dynamic DHCP snooping entry is also added to the
binding table.
- If DHCP snooping is enabled globally, and also enabled on the
VLAN where the DHCP packet is received, but the port is
not trusted
,
it is processed as follows:
* If the DHCP packet is a reply packet from a DHCP server
(including OFFER, ACK or NAK messages), the packet is
dropped.
* If the DHCP packet is from a client, such as a DECLINE or
RELEASE message, the switch forwards the packet only if the
corresponding entry is found in the binding table.
* If the DHCP packet is from client, such as a DISCOVER,
REQUEST, INFORM, DECLINE or RELEASE message, the
packet is forwarded if MAC address verification is disabled (as
specified by the
ip dhcp snooping verify mac-address
command, page 22-16). However, if MAC address verification is
enabled, then the packet will only be forwarded if the client’s
hardware address stored in the DHCP packet is the same as the
source MAC address in the Ethernet header.
* If the DHCP packet is not a recognizable type, it is dropped.
- 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; all static bindings are retained in the
binding table but will have no effect until DHCP snooping is
re-enabled.
•
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 (
ip dhcp snooping trust
, page 22-17).
Note that the switch will not add a dynamic entry for itself to the
Summary of Contents for 7824M/FSW - annexe 1
Page 2: ......
Page 24: ...TABLE OF CONTENTS xxiv ...
Page 28: ...TABLES xxviii ...
Page 32: ...FIGURES xxxii Figure 16 3 DNS Cache 16 7 ...
Page 34: ...GETTING STARTED ...
Page 46: ...SYSTEM DEFAULTS 1 12 ...
Page 62: ...SWITCH MANAGEMENT ...
Page 74: ...CONFIGURING THE SWITCH 3 12 ...
Page 112: ...BASIC MANAGEMENT TASKS 4 38 ...
Page 168: ...USER AUTHENTICATION 6 30 ...
Page 223: ...SHOWING PORT STATISTICS 9 33 Figure 9 12 Port Statistics ...
Page 230: ...ADDRESS TABLE SETTINGS 10 6 ...
Page 304: ...CLASS OF SERVICE 13 16 ...
Page 316: ...QUALITY OF SERVICE 14 12 ...
Page 338: ...MULTICAST FILTERING 15 22 ...
Page 346: ...DOMAIN NAME SERVICE 16 8 ...
Page 348: ...COMMAND LINE INTERFACE IP Interface Commands 35 1 ...
Page 362: ...OVERVIEW OF COMMAND LINE INTERFACE 17 14 ...
Page 494: ...USER AUTHENTICATION COMMANDS 21 48 ...
Page 514: ...CLIENT SECURITY COMMANDS 22 20 ...
Page 540: ...ACCESS CONTROL LIST COMMANDS 23 26 ...
Page 558: ...INTERFACE COMMANDS 24 18 ...
Page 576: ...MIRROR PORT COMMANDS 26 4 ...
Page 582: ...RATE LIMIT COMMANDS 27 6 ...
Page 616: ...SPANNING TREE COMMANDS 29 28 ...
Page 644: ...VLAN COMMANDS 30 28 ...
Page 664: ...CLASS OF SERVICE COMMANDS 31 20 ...
Page 678: ...QUALITY OF SERVICE COMMANDS 32 14 ...
Page 720: ...APPENDICES ...
Page 726: ...SOFTWARE SPECIFICATIONS A 6 ...
Page 730: ...TROUBLESHOOTING B 4 ...
Page 746: ...INDEX Index 6 ...
Page 747: ......