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Good Day

Please help , i have a dhcp on 192.168.21.0/24 and pxe server on 192.168.1.0/24. Now i want to install hosts in 192.168.21.0/24 using this pxe tftp netboot on 192.168.1.0/24. My hosts in 192.168.21.0/24 are getting IP fine then trying tftp to 192.168.1.0/24 its timing out and there is no firewall in between these networks. I can ping across networks fine but i cant tftp netboot. What am i missing. My next-server on 192.168.21.0/24 is the IP of tftp on 192.168.1.10.

I have a cisco 1840 on 192.168.1.0/24 network and also another cisco 1840 on 192.168.21.0/24 network. The second cisco was there to add more other subnets, so it has 192.168.22.0/24, 192.168.21.0/24 and 192.168.20.0/24. So all these subnets connect to a unmanaged switches. Now on this cisco i have 4 wic ports, one goes to the extisting network - 192.168.1.253, then the other three 192.168.21.254, 192.168.22.254 and 192.168.20.3254. there is a cable from this cisco going to a switch in the 192.168.1.0/24 network

I can communicate across these networks , they can talk to each other no issues only this pxe i want to boot from 192.168.21.0/24 network. I am getting TFTP time out soon after a host gets dhcp IP.

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  • Please post a network diagram or explain how these networks are connected.
    – mzhaase
    Feb 24, 2017 at 8:40
  • Thank you mzhaase. I have a cisco 1840 on 192.168.1.0/24 network and also another cisco 1840 on 192.168.21.0/24 network. The second cisco was there to add more other subnets, so it has 192.168.22.0/24, 192.168.21.0/24 and 192.168.20.0/24. So all these subnets connect to a unmanaged switches. Now on this cisco i have 4 wic ports, one goes to the extisting network - 192.168.1.253, then the other three 192.168.21.254, 192.168.22.254 and 192.168.20.3254. there is a cable from this cisco going to a switch in the 192.168.1.0/24 network.
    – Tofara Machemedze
    Feb 24, 2017 at 8:42
  • And the routes are set so that servers from both networks can communicate with each other?
    – mzhaase
    Feb 24, 2017 at 8:44
  • 100% i can communicate across these networks , they can talk to each other no issues only this pxe i want to boot from 192.168.21.0/24 network. I am getting TFTP time out soon after a host gets dhcp IP
    – Tofara Machemedze
    Feb 24, 2017 at 8:46
  • @TofaraMachemedze: Please use the edit button to add this information to your post. Also, use the formatting tools to make it easily readable.
    – Sven
    Feb 24, 2017 at 8:48

1 Answer 1

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Run a Wireshark traffic capture from the DHCP or PXE Server and see what's going on.

1) If you are running a DHCP server with the PXE data enabled and the PXE client on the other subnet gets the IP then it also receives the PXE data (TFTP IP and NBP filename) and your IP helpers are OK but if you use a regular DHCP server with the booting PXE data provided by a proxyDHCP server it could be that the client gets the IP but not the PXE booting info because this info goes on a different port (4011) and probably your DHCP helper is not correctly set for this.

2) TFTP is a protocol that uses port 69 for initiating a transfer but a randomly selected port for the data transfer itself; please check there is not a firewall issue preventing the TFTP data traffic.

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