topic Re: DHCP Relay problems in Switches, Hubs, and Modems

DHCP Relay problems

Darren Dent — Fri, 15 Aug 2008 11:17:25 GMT

Hi

I am having some problems setting up a DHCP Relay on my 4104gl (J4887A). I think I have set it up correctly but it my clients don't seem to be able to see the DHCP server.

Here is what I am trying to do. I have 3 vlans. vlan1 is where I am trying to install the DHCP relay, currently my windows clients are on the same class b subnet 12.24.x.x including the DHCP server (Win2003 - 10.24.4.2) I want to move the DHCP server over to a new class c subnet with the ip address 10.161.236.3 but keeping it on vlan1. I have added the ip helper address into the switch and changed the DHCP server address over to the class c network but the DHCP clients on the existing network don't seem to be able to get any addresses.

I am not sure how I can check to see if it a configuration problem with switch or with my DHCP server.

Here is a copy of the configuration report:

hostname "Procurve1"
cdp run
web-management ssl
module 1 type J4908A
module 2 type J4908A
module 3 type J4862B
module 4 type J4862B
ip default-gateway 10.24.4.1
ip routing
ip timep manual 10.24.4.254 interval 60
snmp-server community "public" Unrestricted
vlan 1
name "DEFAULT_VLAN"
untagged A1-A22,B1,B3-B6,B9-B14,B16-B22,C1-C4,C6-C17,C19-C23,D1-D24
ip address 10.74.4.1 255.255.0.0
ip address 10.24.4.1 255.255.0.0
ip address 10.54.0.1 255.255.0.0
ip address 10.161.236.2 255.255.254.0
ip address 10.48.4.1 255.255.255.0
ip address 10.161.235.2 255.255.255.0
ip helper-address 10.161.236.3
no untagged B2,B7-B8,B15,C5,C18,C24
exit
vlan 2
name "VLAN2"
untagged B7-B8
tagged A21-A22
exit
vlan 99
name "VLAN3"
untagged B2,B15,C5,C18,C24
tagged A21-A22,C15,C17
exit
ip authorized-managers 10.74.0.0 255.255.0.0
ip authorized-managers 10.24.0.0 255.255.0.0
no dhcp-relay
ip route 172.148.96.0 255.255.255.0 10.24.4.254
ip route 172.24.4.0 255.255.255.0 10.24.4.254
ip route 0.0.0.0 0.0.0.0 10.24.4.254
no stack
spanning-tree

I would appreciate any help as I am really stuck!!

Thanks in advance.

Re: DHCP Relay problems

Darren Dent — Fri, 15 Aug 2008 11:23:43 GMT

Sorry I posted the wrong configuration report, here is the correct one:

hostname "Procurve1"
cdp run
web-management ssl
module 1 type J4908A
module 2 type J4908A
module 3 type J4862B
module 4 type J4862B
ip default-gateway 10.24.4.1
ip routing
ip timep manual 10.24.4.254 interval 60
snmp-server community "public" Unrestricted
vlan 1
name "DEFAULT_VLAN"
untagged A1-A22,B1,B3-B6,B9-B14,B16-B22,C1-C4,C6-C17,C19-C23,D1-D24
ip address 10.74.4.1 255.255.0.0
ip address 10.24.4.1 255.255.0.0
ip address 10.54.0.1 255.255.0.0
ip address 10.161.236.2 255.255.254.0
ip address 10.48.4.1 255.255.255.0
ip address 10.161.235.2 255.255.255.0
ip helper-address 10.161.236.3
no untagged B2,B7-B8,B15,C5,C18,C24
exit
vlan 2
name "VLAN2"
untagged B7-B8
tagged A21-A22
exit
vlan 99
name "VLAN3"
untagged B2,B15,C5,C18,C24
tagged A21-A22,C15,C17
exit
ip authorized-managers 10.74.0.0 255.255.0.0
ip authorized-managers 10.24.0.0 255.255.0.0
ip route 172.148.96.0 255.255.255.0 10.24.4.254
ip route 172.24.4.0 255.255.255.0 10.24.4.254
ip route 0.0.0.0 0.0.0.0 10.24.4.254
no stack
spanning-tree

Re: DHCP Relay problems

Matt Hobbs — Fri, 15 Aug 2008 11:27:32 GMT

You have 'no dhcp-relay' in the config but I assume that's only there accidently.

Try creating a DHCP superscope instead on your 2003 server. I believe that's what you're meant to do when multinetting as you're doing.

Is there a reason you are multinetting instead of putting each subnet in its own VLAN?

Re: DHCP Relay problems

Darren Dent — Fri, 15 Aug 2008 11:35:22 GMT

Hi Matt,

Thanks for the fast response.

Yes I did leave the no dhcp-relay in accidentally as I posted an old configuration report.

The reason I am multinetting is because I have been assigned the new class c ip range by the admins of a domain we are setting up a trust with and I didn't want to have to re-ip all of the clients as it isn't necessary. I am not sure how a superscope would work. I still want the DHCP server to assign class b addresses. Perhaps I haven't understood what you mean.

Thanks
Darren.

Re: DHCP Relay problems

Matt Hobbs — Sun, 17 Aug 2008 11:42:40 GMT

Since your server and clients are all in the same VLAN, there is nothing you need to configure at all on the switch.

All you should need to do is create a Superscope on your 2003 DHCP Server:

http://technet.microsoft.com/en-us/library/cc757614.aspx

Also if you haven't done so, I'd start-stop the DHCP service (doesn't like it's IP address being changed).

Re: DHCP Relay problems

cenk sasmaztin — Mon, 18 Aug 2008 07:03:42 GMT

hi Darren
what is dhcp server
default gateway address ?
subnet mask ?

and

scopes address range

cenk

Re: DHCP Relay problems

Darren Dent — Mon, 18 Aug 2008 08:26:37 GMT

Hi Cenk,

Currently the DHCP server (Windows Server 2003) ip configuration is:
ip address: 10.24.4.2
subnet mask: 255.255.0.0 (Class B)
default gateway: 10.24.4.1

It services DHCP clients on the following subnets (all on the same vlan)
10.24.2.x - Static addresses
10.24.3.x - Static addresses
10.24.4.x - Static addresses
10.24.40.100-199 - DHCP Scope
These ranges are used by our dhcp clients (running windows xp/vista)

I want to move the DHCP server onto a new class C subnet with the ip address 10.161.236.3 but I want to keep the DHCP clients on the same class B subnets.

Thanks
Darren.

Re: DHCP Relay problems

cenk sasmaztin — Mon, 18 Aug 2008 12:40:24 GMT

add dhcp server on nic manually second ip address ,subnet mask and default gateway

ip address 10.161.236.3
subnet mask 255.255.254.0
default gateway 10.161.236.2

cenk

Re: DHCP Relay problems

Darren Dent — Mon, 18 Aug 2008 13:10:47 GMT

Hi Cenk,

Thanks for the reply but I don't understand what you mean.

Thanks anyway,
Darren.

Re: DHCP Relay problems

cenk sasmaztin — Mon, 18 Aug 2008 13:53:19 GMT

please you can change dhcp server ip address and test

ip address 10.161.236.3
subnet mask 255.255.254.0
default gateway 10.161.236.2