General discussion


Windows DHCP Server and VLAN

By whang_wesley ·
I have a CISCO catalyst 6500 and I'm using Windows Server 2000 SP4.

What I want is per floor I'll assign diffrent VLAN but seems like we are having problem at the start of the implementation.

The DHCP server is in VLAN1 while the client is on VLAN 20

The client can't obtain an IP address from the DHCP Server

Here are the configuration I did:

interface Vlan20
description 2nd Floor VLAN
ip address
ip helper-address

interface GigabitEthernet3/47
switchport access vlan 40
switchport mode access
no ip address
spanning-tree portfast

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You need to tell VLAN1 about the IP helper address too

by ManiacMan In reply to Windows DHCP Server and V ...

Don't forget that DHCP is a broadcast and routers by default will not transmit any broadcast packets across different broadcast domains. I'm not a Cisco expert, as I am an MCSE, but I can tell you for sure that you have a DHCP relaying problem if your DHCP is on one VLAN/subnet and the PCs' are on another and don't see any DHCP traffic. Do a packet trace and I guarantee you'll confirm that that there is no DHCP traffic hitting your VLAN20 subnet from VLAN1. Also, out of curiosity, try to connect a PC to VLAN1 and see if you get a DHCP assigned address. You'll confirm that your DHCP server is working correctly and if it is, you definitely have a relaying issue with DHCP. Hope this help and please let us know if it fixed your issue. Be sure to give me a thumbs up if this corrected your problem.

Thank you.

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IP Routing

by Roger99a In reply to Windows DHCP Server and V ...

I think you need an "ip routing" statement.

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Couple of things

by khansen In reply to Windows DHCP Server and V ...

Looks like your int gig 3/47 is in the wrong vlan (you have 40, shoudl be 20). Also, on the routing side of things, you need to have an int VLAN 1 defined so that your DHCP server has something to respond back with the DHCP reservation. Try that.

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