Question about Cisco Catalyst 3750E-48PD

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Sending DHCP request across diffrent vlans

Hi i need help routing dhcp packets across a diffrent vlan, The switch connected to dhcp server(vlan 8 ) is cisco 3750 and the host is connected into vlan 2,
Hosts in vlan 8 can get dhcp address, but not the ones in vlan 2.

following is the config of vlan 8 and 2

interface Vlan2
ip address 172.16.0.1 255.255.255.0
ip helper-address 10.20.8.12 (dhcp server address )

interface Vlan8
ip address 10.20.8.1 255.255.252.0

# ip routing is enabled,

I can ping between vlan 2 and vlan 8.

Any help would be higly appreciated.


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Hmm... on your DHCP server, try setting the "default router" IP for each pool to be the VLAN ID on the switch.

scope 172.16.0.0 /24
router 172.16.0.1

scope 10.20.8.0 /22
router 10.20.8.1

I think the DHCP replies aren't going back where they should. I've never done this without a router doing all the DHCP, but it does work and i've done it many times. Your config looks spot on for the switch.

Posted on Feb 05, 2009

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You have 172 network and dhcp in 10 network.
To get ip address from different subnet you should configure DHCP RELAY AGENT on the dhcp server.

Posted on Apr 01, 2009

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