
C
HAPTER
13
| Security Measures
DHCP Snooping
– 444 –
DHCP S
NOOPING
The addresses assigned to DHCP clients on insecure ports can be carefully
controlled using the dynamic bindings registered with DHCP Snooping (or
using the static bindings configured with IP Source Guard). DHCP snooping
allows a switch to protect a network from rogue DHCP servers or other
devices which send port-related information to a DHCP server. This
information can be useful in tracking an IP address back to a physical port.
C
OMMAND
U
SAGE
DHCP Snooping Process
◆
Network traffic may be disrupted when malicious DHCP messages are
received from an outside source. DHCP snooping is used to filter DHCP
messages received on a non-secure interface from outside the network
or fire wall. When DHCP snooping is enabled globally and enabled on a
VLAN interface, DHCP messages received on an untrusted interface
from a device not listed in the DHCP snooping table will be dropped.
◆
Table entries are only learned for trusted interfaces. An entry is added
or removed dynamically to the DHCP snooping table when a client
receives or releases an IP address from a DHCP server. Each entry
includes a MAC address, IP address, lease time, VLAN identifier, and
port identifier.
◆
The rate limit for the number of DHCP messages that can be processed
by the switch is 100 packets per second. Any DHCP packets in excess of
this limit are dropped.
◆
When DHCP snooping is enabled, DHCP messages entering an
untrusted interface are filtered based upon dynamic entries learned via
DHCP snooping.
◆
Filtering rules are implemented as follows:
■
If the global DHCP snooping is disabled, all DHCP packets are
forwarded.
■
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.
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...