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Learn by Doing: Service Template Loops

NSO has a ton of features. This repository is the first of a series which will show a simple use case, along with a feature. The purpose is dual:

  1. See NSO applied to a variety of configuration situations and see how versatile it is..
  2. Learn something new and have an example to follow

This example is a service package deploying:

Radius Configuration

and the feature I am showcasing is:

Service Template XML Loops

This example assumes a working knowledge of services and NSO.

Installation

Reserve the NSO Reservable Sandbox

If you need to revisit some of the NSO Basics, you can start here.

Use some type of file transfer program or VS Code has remote SSH (drag and drop the package into the packages directory)

This repo should go here:

/var/opt/ncs/packages/

If you are repoducing this elsewhere, here are the version details:

using NSO 5.3.0.1
cisco-ios-cli-6.44
on
CSR1000V 16.11.01b

After the package is on the preconfigured NSO system install server (10.10.20.49) at the packages folder, reload packages and configure some sample service instances:

packages reload
conf
radius_server_example first-service-instance device dist-rtr01 radius-servers PRIMARY-SERVER acct-port 1000 auth-port 2000 server-ip 172.10.10.10
exit
radius-servers SECONDARY-SERVER acct-port 1000 auth-port 2000 server-ip 10.150.10.10
commit dry-run outformat native
top
radius_server_example second-service-instance device dist-rtr02 radius-servers OTHER-PRIMARY acct-port 1000 auth-port 2000 server-ip 172.101.1.1
exit
radius-servers OTHER-SECONDARY acct-port 1000 auth-port 2000 server-ip 192.10.20.11
top
commit dry-run outformat native
commit

here is some sample output:

[developer@nso src]$ ncs_cli -C
developer@ncs# packages reload

>>> System upgrade is starting.
>>> Sessions in configure mode must exit to operational mode.
>>> No configuration changes can be performed until upgrade has completed.
>>> System upgrade has completed successfully.
reload-result {
    package cisco-asa-cli-6.8
    result true
}
reload-result {
    package cisco-ios-cli-6.44
    result true
}
reload-result {
    package cisco-iosxr-cli-7.20
    result true
}
reload-result {
    package cisco-nx-cli-5.15
    result true
}
reload-result {
    package radius_server_example
    result true
}
reload-result {
    package resource-manager
    result true
}
developer@ncs#
developer@ncs# conf
Entering configuration mode terminal
developer@ncs(config)# radius_server_example ?
% No entries found
Possible completions:
  <service-instance:string>
developer@ncs(config)# radius_server_example first-service-instance device dist-rtr01 ?
Possible completions:
  radius-servers  <cr>
developer@ncs(config)# radius_server_example first-service-instance device dist-rtr01 radius-servers ?
Possible completions:
  <server-name:string>
developer@ncs(config)# radius_server_example first-service-instance device dist-rtr01 radius-servers PRIMARY-SERVER ?
Possible completions:
  acct-port  auth-port  server-ip  <cr>
developer@ncs(config)# radius_server_example first-service-instance device dist-rtr01 radius-servers PRIMARY-SERVER acct-port 1000 auth-port 2000 server-ip 172.10.10.10
developer@ncs(config-radius-servers-PRIMARY-SERVER)# exit
developer@ncs(config-radius_server_example-first-service-instance)# radius-servers SECONDARY-SERVER acct-port 1000 auth-port 2000 server-ip 10.150.10.10
developer@ncs(config-radius-servers-SECONDARY-SERVER)# top
developer@ncs(config)# radius_server_example ?
This line doesn't have a valid range expression
Possible completions:
  <service-instance:string>  first-service-instance
developer@ncs(config)# radius_server_example second-service-instance device dist-rtr02 radius-servers OTHER-PRIMARY acct-port 1000 auth-port 2000 server-ip 172.101.1.1
developer@ncs(config-radius-servers-OTHER-PRIMARY)# exit
developer@ncs(config-radius_server_example-second-service-instance)# radius-servers OTHER-SECONDARY acct-port 1000 auth-port 2000 server-ip 192.10.20.11
developer@ncs(config-radius-servers-OTHER-SECONDARY)# top
developer@ncs(config)# commit dry-run outformat native
native {
    device {
        name dist-rtr01
        data aaa new-model
             aaa authentication ppp default group radius
             radius server PRIMARY-SERVER
              address ipv4 172.10.10.10 auth-port 2000 acct-port 1000
             !
             radius server SECONDARY-SERVER
              address ipv4 10.150.10.10 auth-port 2000 acct-port 1000
             !
    }
    device {
        name dist-rtr02
        data aaa new-model
             aaa authentication ppp default group radius
             radius server OTHER-PRIMARY
              address ipv4 172.101.1.1 auth-port 2000 acct-port 1000
             !
             radius server OTHER-SECONDARY
              address ipv4 192.10.20.11 auth-port 2000 acct-port 1000
             !
    }
}
developer@ncs(config)# commit
Commit complete.
developer@ncs(config)#

Service Template Loop Statements

The loop statement example can be found in the NSO Development guide PDF with the installation, in chapter 11 Templates.

Basically loop statements allow us to loop over configuration, without using any Python/Java code.

The configuration we want to loop over looks like this:

radius server SERVERNAME
  address ipv4 22.44.55.66 auth-port 125 acct-port 124

And since the IOS NED Yang looks like as follows:

    // radius server *
    list server {
      tailf:info "Server configuration";
      tailf:cli-mode-name "config-radius-server";
      key id;
      leaf id {
        type string {
          tailf:info "WORD;;Name for the radius server configuration";
        }
      }

      // radius server * / address
      container address {
        tailf:info "Specify the radius server address";

        // radius server * / address ipv4
        container ipv4 {
          tailf:info "IPv4 Address";
          tailf:cli-compact-syntax;
          tailf:cli-sequence-commands {
            tailf:cli-reset-siblings;
          }
          leaf host {
            tailf:cli-drop-node-name;
            type inet:host {
              tailf:info "Hostname or A.B.C.D;;IPv4 Address of radius server";
            }
          }
          // alias 1-8 aliases for this server (max. 8)
          leaf auth-port {
            tailf:info "UDP port for RADIUS authentication server (default is 1645)";
            tailf:cli-optional-in-sequence;
            type uint16 {
              tailf:info "<0-65535>;;Port number";
              range "0..65535";
            }
          }
          leaf acct-port {
            tailf:info "UDP port for RADIUS accounting server (default is 1646)";
            type uint16 {
              tailf:info "<0-65535>;;Port number";
              range "0..65535";
            }
          }
        }
      }

We will need to have a unique key to loop over the server id.

In this service package we have the following data model:

module radius_server_example {
  namespace "http://com/example/radius_server_example";
  prefix radius_server_example;

  import ietf-inet-types {
    prefix inet;
  }
  import tailf-ncs {
    prefix ncs;
  }

  list radius_server_example {

    uses ncs:service-data;
    ncs:servicepoint "radius_server_example";

    key service-instance;

    leaf service-instance {
      type string;
    }


    // may replace this with other ways of refering to the devices.
    leaf-list device {
      type leafref {
        path "/ncs:devices/ncs:device/ncs:name";
      }
    }

    list radius-servers{
      key server-name;

      leaf server-name{
        type string;
      }

      leaf server-ip{
      type inet:ipv4-address;
      }

          leaf auth-port {
      type inet:port-number;
    }

    leaf acct-port {
      type inet:port-number;
    }
    }
  }
}

Where we have each service instance defined by a unique string, and the server name is the unique key we will loop over. We have a static part of the configuration at the top of our template that is not looped, and a dynamic part which we want to expand out if there is more than radius server:

      <aaa xmlns="urn:ios">
        <new-model/>
        <authentication>
          <ppp>
            <name>default</name>
            <group>radius</group>
          </ppp>
        </authentication>
      </aaa>

      <radius xmlns="urn:ios">
          <?foreach {/radius-servers}?>
          <server>
            <id>{server-name}</id>
            <address>
              <ipv4>
                <host>{server-ip}</host>
                <auth-port>{auth-port}</auth-port>
                <acct-port>{acct-port}</acct-port>
              </ipv4>
            </address>
          </server>
          <?end?>
        </radius>
      </config>
    </device>
  </devices>
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