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I have a PXE+DHCP server creaed using syslinux and already running on a private network segment (198.19.99.xxx).. I want to know if this PXE+DHCP server can be configured to boot machines over another network segment (172.16.87.xxx)?

If the two networks could communicate with each other then what will be the dhcp.conf file's setting?

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Yes, this is possible provided your target network is configured to relay DHCP and TFTP traffic. You'll likely need IP "helper addresses" on the client's network that point back to the actual DHCP server's IP address.

See: Broadcast between VLANs

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  • It is possible but: 1) The router linking both networks must have the DHCP relay service enabled not the target network. 2) TFTP traffic does not need to be relayed. 3) you do not need IP "helper addresses" at the destination network pointing back to anywhere. – Pat Jan 2 '15 at 20:21
  • It depends on the equipment in use. The standard is to set IP helper addresses in the destination subnet/vlan - serverfault.com/a/416437/13325 – ewwhite Jan 2 '15 at 20:24
  • with all due respect, if you have a router joining both networks you turn on the DHCP relay service. of course you never ever relay TFTP traffic; – Pat Jan 2 '15 at 20:30
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DHCP is based on a "DORA" (Discover-Offer-Request-Accept) protocol; Minimally the Discover packets are broadcasted on a MAC domain by the booting clients searching for a DHCP server. Broadcast traffic is by default blocked by routers, then normally you will not be able to boot PXE clients on network 172.16.87.xxx out of a DHCP server located at 198.19.99.xxx.

But you can enable at the router "linking" both networks a DHCP relay agent (IP Helper) this way the router will take the broadcast request coming from the client at 172.16.87.xxx network and it will uni-cast the request over the DHCP server in the 198.19.99.xxx network.

The routers (not the networks) provide the DHCP relay services. You do not need anything else at the destination. TFTP traffic does not need to be relayed.

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