question about DHCP

Answered Question
Mar 1st, 2009
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there is a computer 1. it is connected to

a layer 3 switch. and DHCP server is connected to layer 3 switch which dosen't not belong to same broadcast domain with computer 1.


in this case, when computer 1 try to discover DHCP server, which step dose

it take?


as I think, first computer 1 send broad

cast packet to in-domain to discover DHCP server. and if there is no reponse,

the switch get the packet and broadcast it to computer which is connected to the switch. and DHCP server got the packet and reponse to computer 1.


is it right that I've understood?



Correct Answer by Joe Clarke about 8 years 3 months ago

The routed interface on the layer 3 switch to which the PC connects must have an ip helper-address configured on it so that the switch knows where to send the DHCP discover. The helper address points to the IP address of the DHCP server. For example:


interface Vlan6

ip address 10.32.6.1 255.255.255.0

ip helper-address 10.32.100.33


Without this, the PC will not be able to get a DHCP offer.


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Correct Answer
Joe Clarke Sun, 03/01/2009 - 21:05
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The routed interface on the layer 3 switch to which the PC connects must have an ip helper-address configured on it so that the switch knows where to send the DHCP discover. The helper address points to the IP address of the DHCP server. For example:


interface Vlan6

ip address 10.32.6.1 255.255.255.0

ip helper-address 10.32.100.33


Without this, the PC will not be able to get a DHCP offer.


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