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[EX] Using DHCP Option 150 on the EX switch to resolve the TFTP server's IP address for auto-installation



Article ID: KB21691 KB Last Updated: 25 Aug 2011Version: 1.0
Auto-installation helps automate the configuration process by automatically loading the configuration files onto EX switches over the network. For the auto-installation process to work, you must store one or more host-specific or default configuration files on a configuration server in the network and have a service available; typically a Dynamic Host Configuration Protocol (DHCP) to assign an IP address to the EX switch.

In the example of this KB, we use a TFTP server as the configuration server, where the configuration file for the new EX switch (client switch) is stored. We use another EX switch as the DHCP server to assign an IP address to the me0 interface for the new EX switch. The DHCP server also passes the TFTP server's IP and the configuration file to the new EX switch.


During the auto-installation process, when the client has difficulty interpreting the TFTP server's IP address passed from the DHCP server, It then goes through the process of locating the TFTP server by sending a broadcast message to address, to find the configuration file that is stored in the TFTP server. It can get stuck at this process for a while and eventually fail. This failure mode can be verified by capturing the packets in and out of the me0 interface.

Include option 150 on the DHCP server and specifying a DNS server to help the client resolve the TFTP server's IP address and locate the configuration file.
  • DNS server:
  • TFTP server:
The following is an example of the DHCP server's configuration and the CLIs for setting up the client switch for auto-installation:

Configuration example on the DHCP Server switch;
root@EX4200-48T# show
name-server {;
boot-file ex_base.conf;
pool {
address-range low high;
router {;
option 150 ip-address;

Below are the CLIs to setup auto-installation on the client:
load factory-default
set system root-authentication plain-text-password
set system autoinstallation delete-upon-commit
set system autoinstallation interfaces me0 bootp

Use show system autoinstallation status to verify that the client obtains the configuration information:
root@clientEX4200> show system autoinstallation status
Autoinstallation status:
Master state: Active
Last committed file: None
Configuration server of last committed file:
Name: me0
State: Configuration Commit
Hostname: None
Hostname source: None
Configuration filename: ex_base.conf
Configuration filename server:
Address acquisition:
Protocol: DHCP Client
Acquired address:

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