When a network device like a switch or a router comes on-line, a fair amount of manual configuration has to happen before it is fully functional. At minimum, it needs to be updated to the proper software image and a golden configuration. Day zero automation techniques automate these processes, bringing up network devices into a functional state with minimal to no-touch. Hence the name Zero touch. The goal of Zero touch is to enable you to plug in a new network device and have it configured and transitioned into production automatically without the need for manual configuration.
Cisco IOS XE supports three Day Zero technologies: Network Plug-N-Play, Zero Touch Provisioning (ZTP) and Preboot eXectuion Environment (PXE). To keep us on track with our goal we will only talk about ZTP here.
On IOS XE ZTP is supported in following ways,
- AutoInstall
All Cisco IOS-XE (and Cisco IOS) based devices try to automatically download a configuration file during the first boot. This is called as Autoinstall. When a IOS device boots, the AutoInstall process tries to download the configuration via TFTP. If a custom TFTP server is used, the configuration provided to the device can be built with information gathered from DHCP Server.
- Python based
When a device that supports python Zero-Touch Provisioning boots up, and does not find the startup configuration (during fresh install on Day Zero), the device enters the Zero-Touch Provisioning mode. The device locates a Dynamic Host Control Protocol (DHCP) server, bootstraps itself with its interface IP address, gateway, and Domain Name System (DNS) server IP address, and enables Guest Shell. The device then obtains the IP address or URL of a TFTP/HTTP server, and downloads the Python script to configure the device. Guest Shell provides the environment for the Python script to run. Guest Shell executes the downloaded Python script and configures the device for Day Zero. After Day Zero provisioning is complete, Guest Shell remains enabled.
- Hybrid(Autoinstall+Python)
On devices that support python ZTP and AutoInstall we can enable hybrid mode. Python based ZTP will always takes priority and will trigger a python script as in option 2 above and if that fails it will fall back to AutoInstall for generic configuration. This generic configuration file must have a hardcode name as cisconet.cfg and placed only in tftp server to be picked up by the device.
DHCP Server Configuration for Python + AutoInstall
DHCP Option 67: http://x.x.x.x/ztp.py
DHCP Option 150: tftp-server-ip
When ZTP runs, option 67 will be used to download and execute ztp.py. When AutoInstall runs, option 150 will be used to download and apply “cisconet.cfg” from the TFTP server
| Platform | ZTP Minimum Release | XE Minimum Release |
|---|---|---|
| Catalyst 9200 | 16.12.1 | 16.9.2 |
| Catalyst 9300/9500 | 16.5.1a | 16.5.1a |
| Catalyst 9800 | 16.12.1 | 16.10.1 |
| ASR 1000 Fixed | 16.7.1 | 3.12.0 (1001-X) / 16.2.1 (1002-HX) |
| ASR 1000 Modular | 16.8.2 | Varies (3.x) |
| Catalyst 8000 | 17.3.2 | 17.3.2 |
HTTP-based download of ZTP Python script available as of 16.8.1.
ZTP not supported in IOS XE 16.12.4 due to a defect.
ZTP solution requires a DHCP server, which will inform the network device about where to find python file/configuration/software image etc to download. This can be a location on the network and can be on a TFTP or HTTP server.
When an XE device boots and there is no config and when DHCP provides option 67 with this python file from repo, it will be automatically downloaded to device and gets executed.
A DHCP server is required for ZTP, as this is how the device learns about where to find the Python configuration file from. In our case, the DHCP server is the open source ISC DHCPd and the configuration file is at /etc/dhcp/dhcpd.conf in a Linux developer box. The option bootfile-name is also known as option 67 and it specifies the python file ztp.py
Below is a sample dhcpd.conf and someuseful commands for ISC DHCP server for your use.
option domain-name "lab_name";
default-lease-time 600;
max-lease-time 7200;
ddns-update-style none;
authoritative;
subnet x.x.x.x netmask x.x.x.x {
range 10.1.1.150 10.1.1.159;
option domain-name "";
option domain-name-servers x.x.x.x;
option subnet-mask x.x.x.x;
option broadcast-address 1x.x.x.x;
option routers x.x.x.x;
option ntp-servers x.x.x.x;
default-lease-time 600000;
max-lease-time 720000;
class "C9300-24T" { match if substring (option vendor-class-identifier,0,15) = "\tC9300-24T"; }
pool {
allow members of "C9300-24T";
deny members of "ciscopnp";
range x.x.x.x x.x.x.x;
option bootfile-name "http://x.x.x.x/ztp.py";
}
cat /etc/dhcp/dhcpd.conf | grep bootfile-name
Example for DHCP Option 67 bootfile-name with HTTP: option bootfile-name "http://x.x.x.x/ztp.py";
ps xa |grep dhcpd
tail -F /var/log/dhcpd.log &
In our case the Python file for ZTP is called ztp.py and is hosted at the webserver root directory which is set within the Apache webserver configuration.
ZTP accesses the python configuration file from HTTP or TFTP server(In our case we use HTTP). Before running ZTP check that the Apache HTTPD server is running with the following commands, this will follow the log file from the webserver so you will see when the file is accessed.
ps xa | grep httpd
tail -F /var/log/httpd/access_log &
Gets downloaded automatically to the device.
Start execution in the guest shell.
Logs ZTP process to persistent storage on the device flash for failure analysis.
Expects input from user about http server address, target version to upgrade/downgrade, image name, image MD5.
checks if upgrade/downgrade required and takes appropriate action.
If upgrade required, transfers image from http server to device flash.
Deploys an EEM script to perform upgrade steps and post upgrade(cleanup) steps.
Runs the EEM script.
Pushes the entire golden config or a partial config.
Notifies user of success/failure on both CLI prompt and logs.
See the support matrix above and use this script accordingly. This script is tested across all XE versions that supports ZTP.
• GuestShell/ZTP needs 1.1GB free space on bootflash. May be unable to launch GuestShell to execute ZTP if < 1.1 GB is free on bootflash.
• Md5 checksum will fail on IOSXE V16.6 and V16.7 due to known issue , so the script will bypass that MD5 checksum on that specific versions and continue with the rest of the workflow
• On 16.6.x and 16.7.x ZTP If image file transfer need to happen , it might intermittently fail for first time and ZTP could report fail ,but an automatic re attempt will be done and it should be successful in the subsequent attempt.
Arun Kumar Sakthivel (arsakthi) [email protected]
Chitransh Pratyush (cpratyus) [email protected]
Log Files from running this Python Script are enabled by default , Logging can be disabled by setting the flag log_tofile = False in the script On IOS XE 17.2.x and above log files are stored at '/flash/guest-share/ztp.log'. In all other version logs will be located at '/flash/ztp.log'
Arun Kumar Sakthivel ([email protected])
Chitransh Pratyush (cpratyus) [email protected]
This project is covered under the terms described in LICENSE
Jeremy Cohoe (jcohoe) [email protected] . His XE ZTP script is a starting point for our codebase.