DHCP across VLAN's.

[Karl Collinson]

Morning Tino,

I had 2 DHCP issues...

One issue was getting the Windows Server 03 DHCP service to issue 2x different IP's\Subnets to the 2x VLAN's i had the server connected to (Server had 2x NICS, each NIC was connected to one of the VLANS)
"That now works"...

The other issue....
I required the DHCP service to relay 2 VLAN1 from VLAN3 so the WiFi router could serice DHCP request... (Router was located in VLAN1)..

Couldnt get round that so easily, so i used a WAP and untagged the port to VLAN3 where the DATA DHCP Service was accessable.

Thx,
Karl.

[Colonelk]

Hi Karl,

I had thought of using 2 Nics (one in each vlan) in that server and may well choose to do that when I do the swap over to the new network. At least then I'll be able to manage DHCP from the one server.

Good luck in your rollout.

Tino

[Joel Belizario]

Tino,

Just to clarify your post - was DHCP was working in every VLAN except 10 or not at all?

[Colonelk]

Hi Joel.

Previously DHCP would work for vlan 1 (the dhcp server was an untagged member of vlan 1) but not for vlan 10. I then tried the ip helper-address function on the switch assigned to vlan 10, pointing to the dhcp server on vlan 1. The IP phones were NOT able to pick up a dhcp assigned address this way.

So yesterday I added another NIC to the DHCP server and made the port the new NIC was attached to an untagged member of vlan 10 (and gave it an Ip address on that subnet). Now phones are able to pick up an address from the correct DHCP scope.

[Joel Belizario]

Is DHCP the only network traffic that is not getting through from VLAN 1 to 10? Or have you found that IP routing does not work at all from VLAN 1?

Just wondering because if you have enabled the "management-vlan" feature on VLAN 1 then it becomes a non-routable VLAN.

[cenk sasmaztin]

hi karl
you can in vlan1 ip routing

you make switch config after dhcp server config

for example
ip routing
name "DEFAULT_VLAN"
untagged 1-10,21-26
ip address 100.100.100.1 255.255.255.0
ip helper-address 100.100.100.80
no untagged 11-20
exit
vlan 10
name "VLAN10"
untagged 11-20
ip address 100.100.110.1 255.255.255.0
ip helper-address 100.100.100.80
exit

dhcp server in vlan 1
scobe1 name :vlan 1
range 100.100.100.10 100.100.100.200 255.255.255.0 default gateway 100.100.100.1
dns 100.100.100.80(my dhcp and dns server nic ip)
scobe2 name:vlan 10
range 100.100.110.10 100.100.110.200 255.255.255.0 default gateway 100.100.110.1
dns 100.100.100.80(my dhcp and dns server)

very easy....

good luck

[Colonelk]

Hi Joel

I didn't realise that no routing occurred on the management vlan. I've set up a data vlan now (vlan 20) and set the management-vlan to vlan 1 (default_vlan)

[Joel Belizario]

Not many people do - I have been caught by this myself.

So does DHCP work in this case now or are you sticking to the dual NICs?

[Colonelk]

I'll stick with the Dual NIC's for now.

When I implement this on the network properly I may try the DHCP helper again. If I do I'll update the thread.

Thanks

Tino