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PowerConnect 7024P VLAN DHCP

Posted on 2013-06-01
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Last Modified: 2016-11-23
I have a Dell PowerConnect 7024P that has both VLAN 1 and VLAN 300 configured.  VLAN 300 is used to support VOIP.  The problem I'm having is that for some reason the DHCP server I have setup to allocate IP addresses to the VOIP phones is allocating addresses to the desktop machines.  I'm confused why this would be happening since I did allocate and IP address for each VLAN interface in order to ensure the request would get handled correctly based on the subnet.  So why does the DHCP server for VOIP hand out IPs to the desktop machines?

Voice VLAN 300

VLAN 1
ip address 172.31.25.252 255.255.255.0

VLAN 300
ip address 172.30.25.252 255.255.255.0
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Question by:lmehlhorn
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by:woolnoir
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you have 2 seperate DHCP servers ? or 1 with 2 scopes ? you have probably set up a 'ip helper' statement somewhere to forward DHCP requests to your DHCP server ? if so, i believe (from memory - gong to check now) this switch only supports 1 helper statement for the whole device and not per vlan DHCP like ciscos.

essentially ALL dhcp requests from your vlans will be forwarded to all DHCP servers, so it may be random.

You could probably setup 1 server, 2 scopes, match the networks with your VLAN definitions and have it working fine.
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by:woolnoir
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somewhere you have these commands right

bootpdhcprelay enable
bootpdhcprelay serverip ip-address

so if you can elaborate on how many DHCP servers you have, 1 per vlan, or 1 for both (with 2 scopes) i can assist further.
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by:lmehlhorn
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Yes, I have to 2 separate DHCP servers setup.  I don't have the boopdhcprelay commands because I didn't think they would be required with the "ip address" set for each VLAN interface.  The way I understand it when the DHCP request is made the VLAN IP/Subnet will determine which DHCP server/scope to poll.
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by:andrew1812
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You just need i dhcp server. Create multiple scopes for the network address you want (vlan 1 and vlan 300). Configure the dhcp server with IP address belonging to vlan 1 or vlan 300. If the dhcp server is on vlan 1 configure IP helper address for the vlan 300 interface on the switch r vice versa.
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by:lmehlhorn
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Okay, I configured a single DHCP server to handle both scopes.  I modified VLAN 300 to have the following configuration.  However, when I plug in the VOIP phone and review the network configuration it still displays the PC subnet 172.31.25.0/24.  I'm assuming that the VOIP phone isn't getting put into VLAN 300 (Voice VLAN) and thus not requesting the correct scope??

interface vlan 300
ip address 172.30.25.252 255.255.255.0
ip netdirbcast
ip helper-address 172.31.25.50 dhcp
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by:woolnoir
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What's the port config on the port with the phone plugged into?
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by:lmehlhorn
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Port is configured as follows based on the running config

interface Gi1/0/1
switchport voice detect auto
spanning-tree portfast
switchport mode general
switchport general allowed vlan add 300 tagged
voice vlan 300
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by:woolnoir
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Are they cisco phones ? do they support the voice vlan feature (its not standard across the board...)
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by:woolnoir
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if its the only device on the port, then just set the native (normal) vlan to be the VOIP vlan. Voice vlan is only really usefull with device chaining i.e port -> phone -> PC.
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by:lmehlhorn
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Yes, they are Cisco 7950 phones .  They are not the only device on the port - they are chained eg Phone - PC.
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by:woolnoir
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So if your problem is that the desktop machines are getting VOIP IP ranges... (as in your original post) you need to specify the non voip vlan on your port ? Set the port vlan to your data VLAN as untagged.
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by:woolnoir
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Although i guess since you are using vlan 1 (default) then all ports not defined will be in 1 by default, but since you have set an allowed list, you should add vlan 1 to that port as untagged too. Do that, and check if it alters the result.
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lmehlhorn earned 0 total points
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Firmware upgrade 5.1.0.1 addressed a bug and fixed the problem
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Author Closing Comment

by:lmehlhorn
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Managed to solve it on my own.
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