
C
HAPTER
29
| General Security Measures
DHCPv4 Snooping
– 1117 –
■
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).
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 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.
E
XAMPLE
This example enables DHCP snooping globally for the switch.
Console(config)#ip dhcp snooping
Console(config)#
R
ELATED
C
OMMANDS
Содержание ECS4660-28F
Страница 1: ...Management Guide www edge core com ECS4660 28F Layer 3 Gigabit Ethernet Switch...
Страница 2: ......
Страница 4: ......
Страница 12: ...ABOUT THIS GUIDE 12...
Страница 64: ...CONTENTS 64...
Страница 90: ...TABLES 90...
Страница 92: ...SECTION I Getting Started 92...
Страница 122: ...SECTION II Web Configuration 122 Multicast Routing on page 825...
Страница 148: ...CHAPTER 3 Using the Web Interface Navigating the Web Browser Interface 148...
Страница 224: ...CHAPTER 5 Interface Configuration VLAN Trunking 224 Figure 68 Configuring VLAN Trunking...
Страница 262: ...CHAPTER 6 VLAN Configuration Configuring VLAN Translation 262...
Страница 304: ...CHAPTER 9 Congestion Control Automatic Traffic Control 304...
Страница 340: ...CHAPTER 11 Quality of Service Attaching a Policy Map to a Port 340...
Страница 452: ...CHAPTER 13 Security Measures DHCP Snooping 452...
Страница 740: ...CHAPTER 17 IP Services Configuring the PPPoE Intermediate Agent 740...
Страница 866: ...CHAPTER 21 Multicast Routing Configuring PIMv6 for IPv6 866...
Страница 882: ...CHAPTER 22 Using the Command Line Interface CLI Command Groups 882...
Страница 1024: ...CHAPTER 26 Remote Monitoring Commands 1024...
Страница 1030: ...CHAPTER 27 Flow Sampling Commands 1030...
Страница 1088: ...CHAPTER 28 Authentication Commands PPPoE Intermediate Agent 1088...
Страница 1162: ...CHAPTER 29 General Security Measures Configuring Port based Traffic Segmentation 1162...
Страница 1186: ...CHAPTER 30 Access Control Lists ACL Information 1186...
Страница 1214: ...CHAPTER 31 Interface Commands Transceiver Threshold Configuration 1214...
Страница 1238: ...CHAPTER 33 Port Mirroring Commands RSPAN Mirroring Commands 1238...
Страница 1258: ...CHAPTER 34 Congestion Control Commands Automatic Traffic Control Commands 1258...
Страница 1270: ...CHAPTER 36 UniDirectional Link Detection Commands 1270...
Страница 1276: ...CHAPTER 37 Address Table Commands 1276...
Страница 1336: ...CHAPTER 39 ERPS Commands 1336...
Страница 1386: ...CHAPTER 40 VLAN Commands Configuring Voice VLANs 1386...
Страница 1406: ...CHAPTER 41 Class of Service Commands Priority Commands Layer 3 and 4 1406...
Страница 1424: ...CHAPTER 42 Quality of Service Commands 1424...
Страница 1536: ...CHAPTER 43 Multicast Filtering Commands MLD Proxy Routing 1536...
Страница 1602: ...CHAPTER 45 CFM Commands Delay Measure Operations 1602...
Страница 1624: ...CHAPTER 47 Domain Name Service Commands 1624...
Страница 1646: ...CHAPTER 48 DHCP Commands DHCP Server 1646...
Страница 1974: ...SECTION IV Appendices 1974...
Страница 1980: ...APPENDIX A Software Specifications Management Information Bases 1980...
Страница 2020: ...ECS4660 28F E102013 ST R03 149100000140A...