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I'm working to configure a Juniper Networks switch through Zero Touch Provisioning. On CentOS 7, the journal/log/(systemd whatever-it-is) contains this:

Nov 28 10:08:46 server dhcpd[8800]: Checking if packet is permitted.
Nov 28 10:08:46 server dhcpd[8800]:     Permit list: unknown clients
Nov 28 10:08:46 server dhcpd[8800]:    OK
Nov 28 10:08:46 server dhcpd[8800]: Checking if packet is permitted.
Nov 28 10:08:46 server dhcpd[8800]:     Permit list: unknown clients
Nov 28 10:08:46 server dhcpd[8800]:    OK
Nov 28 10:08:46 server dhcpd[8800]: matched a Juniper Networks QFX-5100
Nov 28 10:08:46 server dhcpd[8800]: DHCPDISCOVER from 08:b2:58:ab:dc:00 via eth2
Nov 28 10:08:47 server dhcpd[8800]: DHCPOFFER on 192.168.0.100 to 08:b2:58:ab:dc:00 (TR0217010017) via eth2
Nov 28 10:08:47 server dhcpd[8800]: Checking if packet is permitted.
Nov 28 10:08:47 server dhcpd[8800]:     Permit list: unknown clients
Nov 28 10:08:47 server dhcpd[8800]:    OK
Nov 28 10:08:47 server dhcpd[8800]: Checking if packet is permitted.
Nov 28 10:08:47 server dhcpd[8800]:     Permit list: unknown clients
Nov 28 10:08:47 server dhcpd[8800]:    OK
Nov 28 10:08:47 server dhcpd[8800]: matched a Juniper Networks QFX-5100
Nov 28 10:08:47 server dhcpd[8800]: DHCPREQUEST for 192.168.0.100 (192.168.0.250) from 08:b2:58:ab:dc:00 (TR0217010017) via eth2
Nov 28 10:08:47 server dhcpd[8800]: DHCPACK on 192.168.0.100 to 08:b2:58:ab:dc:00 (TR0217010017) via eth2

The server is provisioned from the "unknown" pool. Here are the relevant portions of the config:

# Global options
max-lease-time 1800;
default-lease-time 1800;
dynamic-bootp-lease-length 120;
ddns-update-style none;

# TFTP Server IP and file
next-server 192.168.0.250; # Assumed to be the DHCP server
filename "pxelinux.0";


# Define the pxe grub filename option
option zone-pxegrub-filename code 150 = text;
option zone-pxegrub-filename "/opt/tftp_files/boot/pxelinux.0";

# Options for Juniper switch to download FW and configuration from this server
# as described here: https://www.juniper.net/documentation/en_US/junos/topics/task/configuration/software-image-and-configuration-automatic-provisioning-confguring.html
option space NEW_OP;
option NEW_OP.config-file-name code 1 = text;
option NEW_OP.image-file-name code 0 = text;
option NEW_OP.image-file-type code 2 = text;
option NEW_OP.transfer-mode code 3 = text;
option NEW_OP.alt-image-file-name code 4 = text;
option NEW_OP-encapsulation code 43 = encapsulate NEW_OP;
option option-150 code 150 = ip-address;

# bringing in the vendor specific options
vendor-option-space NEW_OP;
option NEW_OP.image-file-name "/juniper/fw/jinstall-host-qfx-5-17.2R1.13-signed.tgz";
option NEW_OP.config-file-name "/juniper/cfg/qfx-5100.cfg";
option NEW_OP.alt-image-file-name "/juniper/fw/jinstall-host-qfx-5-17.2R1.13-signed.tgz";
option NEW_OP.image-file-type "filename";
option NEW_OP.transfer-mode "tftp";

option option-150 192.168.0.250;


class "workers" {
   match if substring(hardware, 1, 3) = 00:20:0c or substring(hardware, 1, 3) = 00:18:7D;
   log(info, "matched a worker bee");
}

class "monitor" {
   match if substring(hardware, 1, 3) = 00:d0:24;
   log(info, "matched to a monitor");
}

class "JuniperSwitch" {
   match if option vendor-class-identifier ~~ "^juniper-qfx5100.+$";
   log(info, "matched a Juniper Networks QFX-5100");
}

subnet 192.168.0.0 netmask 255.255.255.0 {
   #authoritative;
   option routers 192.168.0.250;
   pool {
      allow members of "workers";
      range 192.168.0.1 192.168.0.99;
      log(info, concat("Issuing DHCP address to worker bootp requestor: ", binary-to-ascii(16, 8, ":", substring(hardware, 1, 6))));
   }
   pool {
      allow members of "monitor";
      range 192.168.0.245;
      log(info, concat("Issuing DHCP address to monitor bootp requestor: ", binary-to-ascii(16, 8, ":", substring(hardware, 1, 6))));
   }
   pool {
      allow members of "JuniperSwitch";
      allow dynamic bootp clients;
      range 192.168.0.201;
   }
   pool {
      allow unknown-clients;
      range 192.168.0.100 192.168.0.150;
   }
}

Please, help me to understand why this isn't giving an address where I expect.

2

Supposing it is the only switch asking for an IP address via DHCP, I suspect this is an old/known ISC DHCP bug/"feature":

dynamic leases already given take precedence from some other new configurations, especially when they are in the same network.

So to speak, the switch got an address from the general/"unknown" pool before you configured the specific case, and the DHCP daemon gives priority to that.

Either you delete the DHCP leases file var/lib/dhcp/dhcpd.leases , or stop the DHCP service and edit out all the occurrences of any IP address leases given to the MAC of the switch in question from the leases file. That way, it will get the intended new address.

  • 1
    Thank you. This was indeed the problem. I stopped the service and deleted the leases file. After restarting the server, I zeroed the switch and rebooted. It was vended the expected address. This makes sense but I couldn't rule out my config. Before this project, it had been many years since I'd configured dhcpd, and I'd never done anything this complicated. – Andrew Falanga Nov 28 '17 at 22:29
  • @AndrewFalanga This is a though one for people caught unaware...I had to forbid people having a floating dynamic IP address to conveniently configure new printers before they were "officially" provisioned. It can literally drive you up the wall for days – Rui F Ribeiro Nov 28 '17 at 22:46
  • thanks for the heads up. The application I have may not require this, but I'll keep it in mind. – Andrew Falanga Nov 28 '17 at 23:01

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