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PXE IP for different subnets

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wblum
Occasional Visitor

PXE IP for different subnets

Procurve 5372 XL
We are using VLAN 1 as the only VLAN.
We have established 4 subnets (10.148.16.0/24, *.17.0/24, *.18.0/24, *.19.0/24.)
IP routing is activated.
On 10.148.16.141 a DHCP server is working.
IPs are to be distributed for all subnets, starting with 16.0.
DHCP relay in VLAN 1 is enabled, ip helper-address is set to 10.148.16.141.
Problem:
IP distribution is o n l y available for subnet 16.0.
show dhcp is saying:
(i.e ) 724 valid client requests, 127 valid server answers, 47 dropped server responses. The number of valid server answers is not increasing any more.
(All 127 IP are from 16.0 subnet).

What to do, in order to receive IP for the other subnets?
6 REPLIES
Matt Hobbs
Honored Contributor

Re: PXE IP for different subnets

What I imagine is happening is that a client sends out a DHCP broadcast to get an address. The DHCP server sees this and since the DHCP server's IP address is on the 16.148.16.x range, it will give a 16.x address.

What I think you may be able to do to workaround this is to assign the DHCP server 3 additional IP adddresses, one in each subnet range. Clients will then randomly be assigned addresses.

This is not ideal though. Is there a reason all these subnets are in the 1 VLAN? Most setups would usually have 4 VLANs set, one of each subnet. That way the DHCP server would only need to have the one IP address as well.

Alternatively you could just use a larger subnet address for the 16 address, if you use 255.255.252.0 it will cover all IP addresses up to 10.148.19.254.

Don't forget to assign points to posts that have helped you.

Matt
wblum
Occasional Visitor

Re: PXE IP for different subnets

What is strange too:

The (main) IP address of the Switch and the VLAN 1 is 193.7.62.250.
The DHCP server (10.148.16.141) is designated to distribute via DHCP some IPs in the 193.X network as well as in all the subnets 10.148.*
Distributing IPs in the ranges of 10.148.17.0, *.18.* and *.19.* network are totally refused.

The counter of valid server answers is sticked to 127.

Changing the netmask in the 10.148.16.0 is showing no positive effect.


Matt Hobbs
Honored Contributor
Solution

Re: PXE IP for different subnets

You would probably need to remove the 17,18,19 subnets for the larger 16 subnet to work. May need to restart the DHCP service (assuming windows server based).
wblum
Occasional Visitor

Re: PXE IP for different subnets

Finally we found the solution!

After we had installed a new LINUX-Server to distribute (parallelly) via DHCP IPs for the same subnets structure we found out that this was working well.
The problem was not the configuration of the switch, but most probably the configuration of the DHCP service.
So we told the our domain admins to have a nearer look at the Windows2003-DHCP-Server.
They forgot to configure the superscope there.
After doing so everything is now working fine.

Thanks for your support Matt!

wblum
Matt Hobbs
Honored Contributor

Re: PXE IP for different subnets

No problem. Don't forget to assign points to posts that helped you:

How Do I Assign Points?

Only the question author can assign points to a given response. If you submit a question or new topic and another member replies to it, you will see a dropdown menu of points next to the reply (you must be logged in to see the menu). Select the point value and then click the "submit points" button. Note that you can rate multiple replies and submit them at one time.

Matt Hobbs
Honored Contributor

Re: PXE IP for different subnets

I spoke too soon again. Thankyou!