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  Asked: Apr 19 2008   1:21 PM GMT
  Asked by: 310329

one dhcp server for 2 vlans with different subnets


Switches, Layer 3-7 Switches, DHCP, VLAN

hi all

how do i configure a same dhcp for two different vlans.
my setup is say vlan 10 is having dhcp server with IP 10.102.1.2
vlan 10 wiht subnet 10.102.1.1/16

vlan 170 with subnet 192.168.10.1/22

vlan 10 clients are getting dhcp, then what i have to configure in layer advanced switch to do get the dhcp ip from vlan 10 dhcp server to vlan 170 clients.

f.y.i intervlan routing is happening between two vlans

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Last Answered: Apr 19 2008  3:37 PM GMT  by Leeying


Latest Contributors: Wrobinson


It depends....

If you are using layer 3 switches and Windows DHCP then just configure the scopes according to the ranges per vlan and also ensure that the DHCP relay is configured on the switches. (http://support.microsoft.com/kb/120932). I cannot say for other DHCP servers like ISC or DNSMASQ, but this is based on a standard so it may work the same.

If you are using a layer 2 switch then you need to have two NICs on the DHCP server to do the job.

If you are using Cisco devices to hand out the addresses then this article (http://articles.techrepublic.com.com/5100-1035_11-5690240.html) may help as the two suggestions above would not be applicable.

HTH
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310329  |   Apr 20 2008  4:38PM GMT

yes realy sir…

but i am geting dhcp ip for vlan 10 from the respective DHCP server.. my issue i wnat to get dhcp IP from that vlan 10 dhcp server to vlan 170 clients also….

but that vlan 10 traffic should be on vlan 170..

i cant change in each n every laptop..
for ur information am using layer 3 advanced switch to do this..

i also tried by enabling the IP helper in the switch but it is not happening ..

please advice me how to handle this… but it is possible.. but some where i am lagging.. i want that tip…

with regards

sathish
Network support engr.

 

Labnuke99  |   Apr 21 2008  1:43PM GMT

You will need to configure the switch ports to be access ports for the VLAN where you desire these devices to be. This enables the switch to forward the DHCP requests tagged with the appropriate subnet request.

 

Snapper70  |   Apr 25 2008  9:07PM GMT

In a Cisco switch/router config, you’d put (in the vlan configuration for 170) something like:

IP helper-address 10.102.1.2

This will direct the DHCP broadcast requests to the server with multiple scopes defined. It will then know enough to forward the response back to the originating router via the giADDR field, who will in turn send the packet out to the requesting client.

If your routing works properly between the 2 subnets, AND you can put the “helper-address” or equivalent into the routing portion of the switch, AND the corresponding scope is properly defined, those clients should get DHCP addresses.