Question : PXE Boot Problem on VLAN using IP helpers

hello there-

im having some trouble with configuring a PXE boot. the situation is as following:

- we have a network with several VLAN's all on HP Switches.
- we have a DHCP and a PXE Boot Server that are both in the same VLAN.
- we have clients in all the other subnets that will need to be able to boot from the PXE server
- using Option43 on DHCP is not an option since it dont work with all hardware that we have in use

Toplogy:

192.168.A.1 = Main Switch / Layer3
192.168.A.2= First building switch - connected to main switch
192.168.A.3=Second building switch - connected to main switch
192.168.A.4=fourth building switch - connected to main switch
192.168.A.5=fifth building switch - connected to main switch

192.168.A.6=sub building switch - connected to 192.168.A.5
192.168.A.7=sub building switch - connected to 192.168.A.5
192.168.A.8=sub building switch - connected to 192.168.A.

every switch has one IP in every VLAN.
Clients will use the corresponding gateway - for 192.168.B.0/24 gateway = 192.168.B.1
on every switch, in every VLAN except the first one, we have IP Helper adresses.
the first ip helper points to our DHCP server
the second ip helper points to our Columbus / PXE server

- now what happens:
- sometimes machine dont get any response from DHCP
- sometimes machine gets response from DHCP but then fails with TFTP of the columbus.
- sometimes we see one gateway, sometimes we see 2, sometimes 3 on the PXE boot info.

all of our switches is HP equipment.
Has anyone had something like this before, or a clue why the system behaves like this?
were pretty stuck here, every of our consultants says something different about it, we tried all of the solutions, no change....

regards
Tiz

Answer : PXE Boot Problem on VLAN using IP helpers

this my working configuration

the dhcp should point to tftp server.
this is my dhcpd.conf

deny unknown-clients;
not authoritative;
option subnet-mask 255.0.0.0;
allow bootp;
allow booting;
ddns-update-style ad-hoc;

subnet 10.0.0.0 netmask 255.0.0.0 {
                                #option routers;
                                option broadcast-address 10.255.255.255;
}

group hosts {
                next-server 10.0.0.251;
                filename "pxelinux.0";

                host host1 {
                                hardware ethernet 00:11:22:33:44:5;
                                fixed-address 10.0.0.1;
                                }
                }

dont forget to restart after change

the tftp  should run on the same server as the dhcp.
the tftp directory /tftpboot should have 777 permissions