DHCP on a 8300

[Ickthoose]

My customer wanted to separate their servers from their pcs so I built 3 (they have three different schools in their district) additional VLANs for them:

(ALL TESTS WERE DONE ON THE 8300 – THE DHCP SERVER IS CONNECTED TO THE 8300.)



VLAN - 20 172.19.1.1 School 1

VLAN - 21 172.20.1.1 School 2

VLAN - 22 172.21.1.1 School 3



Their DHCP server resides at 172.20.0.11 (Vlan 3 on the 8300) The customer made a new scope and enabled it for the new VLAN.


I built a entry under IP -> DHCP-GRT -> of 172.20.1.1 (school 2) to 172.20.0.11 (DHCP server) which should be needed because the DHCP server is on another subnet and enabled it.



I change my port to have a default VLAN of 21 and set my laptop to configure IP automatically. I do not get an IP - it just times out.



If I statically set my NIC to 172.20.1.100/24 GW 172.20.1.1 I can ping the DHCP server at 172.20.0.11 and it can ping me so it looks like the switch is set up correctly.



If we change it back to the default of VLAN 3 172.20.0.1 it works just fine. The only difference between the setups is the DHCP server already resides on 172.20.0.X which is the same subnet as VLAN 3. I did try taking the DHCP-GRT statement out but it didn’t help. Obviously there isn’t a statement for the 172.20.0.x network because it doesn’t have to cross networks.


Am I missing something or is the customer?

 

[andy88]

You need to enable dhcp-relay to pass the requests from vlans 20,21,22 to vlan 3

You will need to create an agent for the vlans and enable relay on each vlan.

Should be something like this.

Done for each vlan interface

config ip dchp-relay enable-fwd-path agent 172.19.1.1 server 172.20.0.11 mode dhcp

conf vlan <20-22> ip dhcp-relay broadcast mode dhcp

 

[Ickthoose]

Thanks Andy - I'll look into enabling the dhcp-relay broadcast mode on the vlan. That seems to be the part I'm missing.
Appreciate the reply!

 

[Ickthoose]

Andy, that was it - just didn't have it turned on in the vlans - thanks.

Michael