Multiple VLAN -> IP Helper -> Microsoft DHCP

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Nerdbert
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Joined: 10 Mar 2014 10:57

Multiple VLAN -> IP Helper -> Microsoft DHCP

Post by Nerdbert » 27 Mar 2014 06:54

Hello friends,

first of all i would like to thank everyone for the help i already received in this forum. It is very very high appreciated!

I've got the following situation. I configured a switch with three different VLANs and connected a client to each port. On the switch there is also a IP Helper adress for each VLAN configured. It looks like this:

ip interface "VLAN50" address 10.0.50.1 mask 255.255.255.0 vlan 50 ifindex 2
ip interface "VLAN60" address 10.0.60.1 mask 255.255.255.0 vlan 60 ifindex 3
ip interface "VLAN70" address 10.0.70.1 mask 255.255.255.0 vlan 70 ifindex 4

vlan 50 enable name "VLAN 50"
vlan 50 port default 1/1
vlan 60 enable name "VLAN 60"
vlan 60 port default 1/2
vlan 70 enable name "VLAN 70"
vlan 70 port default 1/3

ip helper per-vlan only
ip helper address 172.16.43.1 vlan 50
ip helper address 172.16.43.1 vlan 60
ip helper address 172.16.43.1 vlan 70

In addition to that I have a WIndows Server 2k8 running as DHCP Server. I configured 3 DHCP scopes on the Server.

Now how can I tell the DHCP Server to use Scope 3 for VLAN 70, 60 for 2 and so on. Is the only possible way to assign the DHCP Server multiple addresses in the different vlans?

Regards,
nerdbert

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tot3nkopf
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Re: Multiple VLAN -> IP Helper -> Microsoft DHCP

Post by tot3nkopf » 27 Mar 2014 08:38

By my knowledge this will be done by the DHCP server based on source address (from which it receives the request).

Nerdbert
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Posts: 7
Joined: 10 Mar 2014 10:57

Re: Multiple VLAN -> IP Helper -> Microsoft DHCP

Post by Nerdbert » 27 Mar 2014 08:45

Yes, i just couldnt believe it works automatic.

But when a switch relays a DHCP request, he adds a field that is called "GIADDR". He inserts his own ip address of the same VLAN in that field. When the DHCP Server receives the request he looks in that GIADDR field and checks if he has any available DHCP scopes in the same range and gives out a lease.

Pretty simple, i love it :)

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