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Nexus Switching 2nd Edition

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DHCP snooping is the traffic cop between untrusted h<strong>os</strong>ts <strong>and</strong> trusted DHCP servers. DHCP<br />

snooping performs the following responsibilities:<br />

• Validates DHCP messages received from untrusted sources <strong>and</strong> filters out invalid<br />

messages<br />

• Builds <strong>and</strong> maintains the DHCP snooping binding database, which contains<br />

information about untrusted h<strong>os</strong>ts with leased IP addresses<br />

• Uses the DHCP snooping binding database to validate subsequent requests from<br />

untrusted h<strong>os</strong>ts<br />

Note<br />

By default, the feature is inactive on all VLANs; DHCP snooping is enabled on a per-<br />

VLAN basis.<br />

Example 5-62 shows how to enable <strong>and</strong> verify the DHCP snooping process/feature.<br />

Example 5-62. Enabling the DHCP Snooping Process/Feature<br />

Click here to view code image<br />

Egypt# show feature | i dhcp-snooping<br />

dhcp-snooping 1 disabled<br />

Egypt# conf t<br />

Enter configuration comm<strong>and</strong>s, one per line. End with<br />

CNTL/Z.<br />

Egypt(config)# feature dhcp<br />

Egypt(config)# show feature | i dhcp-snooping<br />

dhcp-snooping 1 enabled<br />

Egypt(config)#<br />

Egypt(config)# show running-config dhcp<br />

!Comm<strong>and</strong>: show running-config dhcp<br />

!Time: Thu Oct 1 18:08:40 2009<br />

version 5.2(3a)<br />

feature dhcp<br />

service dhcp<br />

ip dhcp relay<br />

Egypt(config)#

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