BigIron RX Series Configuration Guide
995
53-1001810-01
DHCP snooping
35
How DHCP snooping works
When enabled on a VLAN, DHCP snooping stands between untrusted ports (those connected to
host ports) and trusted ports (those connected to DHCP servers). A VLAN with DHCP snooping
enabled forwards DHCP request packets from clients and discards DHCP server reply packets on
untrusted ports, and it forwards DHCP server reply packets on trusted ports to DHCP clients, as
shown in the following figures.
FIGURE 129
DHCP snooping at Work - on untrusted port
FIGURE 130
DHCP snooping at Work - on trusted port
System reboot and the binding database
To allow DAI and DHCP snooping to work smoothly across a system reboot, the binding database is
saved to a file in the system flash memory after the user issues the "reload" command. DHCP
learnt entries are written to the system flash memory before the router reboots. The flash file is
written and read only if DHCP snooping is enabled.
Configuring DHCP snooping
Configuring DHCP snooping consists of the following steps.
1. Enable DHCP snooping on a VLAN. Refer to
“Enabling DHCP snooping on a VLAN”
on page 996.
2. For ports that are connected to a DHCP server, change their trust setting to trusted. Refer to
“Enabling trust on a port”
on page 996.
Foundry Device
Trusted
Un trusted
reply packet
DHCP server
DHCP
Server
Snooping
DHCP
request packet
DHCP client
DHCP
Client
Foundry Device
DHCP server
reply packet
Trusted
Untrusted
DHCP
Server
DHCP
Snooping
Summary of Contents for Brocade DCX
Page 40: ...xl BigIron RX Series Configuration Guide 53 1001810 01 ...
Page 72: ...lxxii BigIron RX Series Configuration Guide 53 1001810 01 ...
Page 88: ...16 BigIron RX Series Configuration Guide 53 1001810 01 Searching and filtering output 1 ...
Page 300: ...228 BigIron RX Series Configuration Guide 53 1001810 01 Displaying IP information 7 ...
Page 318: ...246 BigIron RX Series Configuration Guide 53 1001810 01 Deploying a LAG 8 ...
Page 418: ...346 BigIron RX Series Configuration Guide 53 1001810 01 SuperSpan 12 ...
Page 482: ...410 BigIron RX Series Configuration Guide 53 1001810 01 MRP CLI example 14 ...
Page 506: ...434 BigIron RX Series Configuration Guide 53 1001810 01 Displaying VSRP information 15 ...
Page 582: ...510 BigIron RX Series Configuration Guide 53 1001810 01 Viewing Layer 2 ACLs 20 ...
Page 634: ...562 BigIron RX Series Configuration Guide 53 1001810 01 Troubleshooting ACLs 21 ...
Page 642: ...570 BigIron RX Series Configuration Guide 53 1001810 01 Trunk formation 22 ...
Page 746: ...674 BigIron RX Series Configuration Guide 53 1001810 01 Displaying RIP filters 24 ...
Page 808: ...736 BigIron RX Series Configuration Guide 53 1001810 01 Displaying OSPF information 25 ...
Page 938: ...866 BigIron RX Series Configuration Guide 53 1001810 01 Displaying MBGP information 27 ...
Page 950: ...878 BigIron RX Series Configuration Guide 53 1001810 01 Using secure copy 28 ...
Page 988: ...916 BigIron RX Series Configuration Guide 53 1001810 01 Clearing IS IS information 29 ...
Page 1054: ...982 BigIron RX Series Configuration Guide 53 1001810 01 Sample 802 1x configurations 33 ...
Page 1108: ...1036 BigIron RX Series Configuration Guide 53 1001810 01 sFlow 39 ...
Page 1190: ...1118 BigIron RX Series Configuration Guide 53 1001810 01 Displaying RIPng information 44 ...
Page 1270: ...1198 BigIron RX Series Configuration Guide 53 1001810 01 Displaying ACLs 47 ...
Page 1310: ...1238 BigIron RX Series Configuration Guide 53 1001810 01 Displaying OSPFv3 information 48 ...
Page 1382: ...1310 BigIron RX Series Configuration Guide 53 1001810 01 Commands That Require a Reload D ...
Page 1435: ...BigIron RX Series Configuration Guide 1363 53 1001810 01 VSRP E ...
Page 1436: ...1364 BigIron RX Series Configuration Guide 53 1001810 01 VSRP E ...