Using cisco router as dhcp gateway

Unanswered Question
Oct 23rd, 2008
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I have a cisco 3825 router. On the f0/1 interface:

int f0/1

ip address

ip address secondary


I have defined a dhcp ip pool based on this 2 subnets. However, I found out that the secondary will never be used even though the primary pool was full!!

Can I know whether there is any command that I need to turn on in order to let the router to assign the ip pool based on secondary ip subnet?

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ARUNPRABHU A Fri, 10/24/2008 - 00:06
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I think Your option of making the second pool to work when the primary DHCP pool fulfilled will not work, But you can try the below option to obtain the same.

Create 2 sub interfaces in the f0/1 interface and assign ip address to each sub-interface.

Whereas in your Switch you need to make the port connecting to the router as a trunk port. and configure 2 vlan in the switch say 1 and 2.

Assign switch ports to vlan based on your requirement.

Now your router will release IP's from both pools, based on the port( VLAN ) to which your user connected.

Warm Rgds, Arun

Giuseppe Larosa Fri, 10/24/2008 - 00:13
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Hello Chris,

the better solution is probably that suggested by Arun.

I've found a doc that explains that in a scenario like yours the primary address pool needs commands to monitor its usage level.


Hope to help



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