How to automate your Cisco legacy network with Ansible

In the previous article , we introduce ansible with NXOS devices. We can also use ansible for Catalyst, NXOS, NXOS-ACI, etc.

Ansible can be very useful to search something or to backup your configuration.

Example to save your configuration :

---

  - name: Configure IOS
    hosts: routers
    connection: local
    gather_facts: False
    any_errors_fatal: true

    tasks:

      - name: show running
        ios_command:
          commands:
            - 'show run'
        register: running_config
        tags:
        - backup

      - name: save output
        copy: content="{{running_config.stdout[0]}}" dest="./output/{{inventory_hostname}}-show_run.txt"
        tags:
        - backup

In the last part, I use the save my output with register: running_config and then I use the module copy to create a new file with the content save in running_config.

You need to create first the directory named here output. After Ansible will create a file with the device name as prefix and concatenate -show_run.txt

copy: content="{{running_config.stdout[0]}}" dest="./output/{{inventory_hostname}}-show_run.txt"

root@09cf326cc275:/ansible/NXOS#  tree output/
output/
|-- R7-show_run.txt
`-- R7.txt

Inside the file you will have your running configuration.

Playbooks are now mandatory, you can also use ad hoc command to search something on your device.

Example with show ip arp or show version

ansible R7 -i inventory-home -m ios_command -a "commands='show ip arp'"                            
 R7 | SUCCESS => {
     "changed": false, 
     "stdout": [
         "Protocol  Address          Age (min)  Hardware Addr   Type   Interface\nInternet  10.0.100.1              0   000c.2935.812f  ARPA   Ethernet0/0\nInternet  10.0.100.67             -   aabb.cc00.7000  ARPA   Ethernet0/0\nInternet  10.0.100.150            1   a483.e7bf.9979  ARPA   Ethernet0/0"
     ], 
     "stdout_lines": [
         [
             "Protocol  Address          Age (min)  Hardware Addr   Type   Interface", 
             "Internet  10.0.100.1              0   000c.2935.812f  ARPA   Ethernet0/0", 
             "Internet  10.0.100.67             -   aabb.cc00.7000  ARPA   Ethernet0/0", 
             "Internet  10.0.100.150            1   a483.e7bf.9979  ARPA   Ethernet0/0"
         ]
     ]
 }

root@09cf326cc275:/ansible/NXOS# ansible R7 -i inventory-home -m ios_command -a "commands='show version'"

Currently we use only show command, but you can also configure your catalyst devices. The following task will enable ospf on all interfaces. I added a tag named OSPF to be able to play only OSPF task within my playbook.

---

  - name: Configure IOS
    hosts: routers
    connection: local
    gather_facts: False
    any_errors_fatal: true

    tasks:
      - name: Enable ospf
        ios_config:
          lines:
            - network 0.0.0.0 255.255.255.255 ar 0
          parents: router ospf 1
        register: ospf
        tags:
        - OSPF

      - debug: var=ospf
        tags:
        - OSPF
root@09cf326cc275:/ansible/NXOS# ansible-playbook -i inventory-home playbook-ios.yaml --tags OSPF
 PLAY [Configure IOS] *
 TASK [Enable ospf] ***
 changed: [R7]
 TASK [debug] *
 ok: [R7] => {
     "ospf": {
         "banners": {}, 
         "changed": true, 
         "commands": [
             "router ospf 1", 
             "network 0.0.0.0 255.255.255.255 ar 0"
         ], 
         "failed": false, 
         "updates": [
             "router ospf 1", 
             "network 0.0.0.0 255.255.255.255 ar 0"
         ]
     }
 }
 PLAY RECAP ***
 R7                         : ok=2    changed=1    unreachable=0    failed=0    skipped=0    rescued=0    ignored=0   

Other example to search an Endpoint on your network with ad hoc command. Here I want to search one server with the @MAC : ecbd.1d44.b6c1.

root@09cf326cc275:/ansible/NXOS# ansible SW1 -i inventory-home -m ios_command -a "commands='show mac address'"  | egrep -v "\n"       
SW1 | SUCCESS => {
    "stdout": [
    ], 
        [
            "Mac Address Table", 
            "-------------------------------------------", 
            "", 
            "----    -----------       --------    -----", 
            "   1    0050.2935.812f    DYNAMIC     Gi0/0", 
            "   1    0050.8824.7718    DYNAMIC     Gi0/0", 
            "   1    0050.bdf0.b6ad    DYNAMIC     Gi0/0", 
            "   1    0050.1878.2797    DYNAMIC     Gi0/0", 
            "   1    0050.9110.af2c    DYNAMIC     Gi0/0", 
            "   1    0050.e7bf.9979    DYNAMIC     Gi0/0", 
            "   1    0050.cc00.2011    DYNAMIC     Gi0/0", 
            "   1    0050.cc00.7000    DYNAMIC     Gi0/0", 
            "   1    0050.eba6.c667    DYNAMIC     Gi0/0", 
            "   1    0050.8b57.d81b    DYNAMIC     Gi0/0", 
            "   1    0050.817a.ce2e    DYNAMIC     Gi0/0", 
            "   1    ecbd.1d44.b6c1    DYNAMIC     Gi0/0", 
            "   1    0050.754a.a8ee    DYNAMIC     Gi0/0", 
        ]
    ]
}

root@09cf326cc275:/ansible/NXOS# ansible catalyst -i inventory-home -m ios_command -a "commands='show mac address'"  | egrep -v "\n" | grep "SUCCESS \|ecbd.1d44.b6c1"
SW1 | SUCCESS => {
            "   1    ecbd.1d44.b6c1    DYNAMIC     Gi0/0",

Here I have found the server on switch SW1 port Gi0/0, which is an uplink port. If I added other switch in my group named catalyst, I’ll be able to found on all switches where is learned this @MAC.

In your inventory file, you need to use groups to organize properly your network. It can be very useful to run one command to only one part of your network or to all.

In the following example we have on DC named DC1 with two different rooms. Each room contains two switches. Now, you can run command only to switches in the Room1 or Room2 or all inside DC1.

[DC1:children]
Room1
Room2

[Room1]
DC1-SW1
DC1-SW2

[Room2]
DC1-SW10
DC1-SW11

How to Automate Cisco NXOS infrastructure with Ansible

You manage a lot of network devices, but you are alone or you don’t have time. Ansible can help you to manage your change on your whole network very quickly based on your own template. In this article we will use Cisco Nexus 9K.

You have a new DNS server, syslog server etc and you need to modify hundred switches. No worries, with ansible it can be very simple.

First you should create at least two files. The first one will be your inventory and contains your switches. The second will be your playbook.

The first thing is to create a service account for ansible in your switches. This account could be centralize or local. In the following I’ll provide my password in cleartext. Of course, it’s not recommended and you should prefer ssh-key.

On my virtual nexus 9k, I only configured my account and my management IP address.

My topology contains :

  • Nexus-1 : IP 10.0.100.99, name: AGG1
  • Nexus-2 : IP 10.0.100.100, name: ACC1
  • Nexus-3 : IP 10.0.100.101, name: ACC2
switch(config-if)# sh run 

!Command: show running-config
!Running configuration last done at: Sat Mar 21 18:28:03 2020
!Time: Sat Mar 21 18:29:45 2020

version 9.3(2) Bios:version  
[..]
username ansible password 5 $5$.FhD0kmO$4PJV/HKJN5ul9aK7160ii.1WQ3s9pjh2QCRL7x7l
EU/  role network-admin
username ansible passphrase  lifetime 99999 warntime 14 gracetime 3
ip domain-lookup

[..]
interface mgmt0
  vrf member management
  ip address 10.0.100.100/24
line console
line vty

The inventory file will be the following. We can use two formats: YAML or INI. This one will use the INI format. This file contains a group named N9K with three switches.

[N9K]
AGR1 ansible_host=10.0.100.99  ansible_port=22
ACC1  ansible_host=10.0.100.100 ansible_port=22
ACC2  ansible_host=10.0.100.101 ansible_port=22

[N9K:vars]
ansible_user=ansible
ansible_password=@ns1b!E.
ansible_connection=network_cli
ansible_network_os=nxos
ansible_python_interpreter="/usr/bin/env python"

The following file uses the YAML format. This first playbook is very simple and contains one task to configure the switch hostname.

---
- name: Setup Nexus Devices

  hosts: all
  connection: local
  gather_facts: False


  tasks:

    - name: configure hostname
      nxos_config:
        lines: hostname {{ inventory_hostname }}
        save_when: modified

Now I’ll verify my playbook, before apply the changes. This command uses the option -i to specify which file should be use as inventory and –check to simulate the changes.

root@09cf326cc275:/ansible/NXOS# ansible-playbook -i inventory-home playbook-home.yaml --check

PLAY [Setup Nexus Devices] ***********************************************************************************************************************

TASK [configure hostname] ************************************************************************************************************************
[WARNING]: Skipping command `copy running-config startup-config` due to check_mode.  Configuration not copied to non-volatile storage
terpreter_discovery.html for more information.
changed: [ACC1]
changed: [AGR1]
changed: [ACC2]

PLAY RECAP ***************************************************************************************************************************************
ACC1                       : ok=1    changed=1    unreachable=0    failed=0    skipped=0    rescued=0    ignored=0   
ACC2                       : ok=1    changed=1    unreachable=0    failed=0    skipped=0    rescued=0    ignored=0   
AGR1                       : ok=1    changed=1    unreachable=0    failed=0    skipped=0    rescued=0    ignored=0 

Now I’ll do the same without the option –check and my Nexus device should be configured. You can see the message copy running is not there.

root@09cf326cc275:/ansible/NXOS# ansible-playbook -i inventory-home playbook-home.yaml        

PLAY [Setup Nexus Devices] ***********************************************************************************************************************

TASK [configure hostname] ************************************************************************************************************************

changed: [ACC1]
changed: [AGR1]
changed: [ACC2]

PLAY RECAP ***************************************************************************************************************************************
ACC1                       : ok=1    changed=1    unreachable=0    failed=0    skipped=0    rescued=0    ignored=0   
ACC2                       : ok=1    changed=1    unreachable=0    failed=0    skipped=0    rescued=0    ignored=0   
AGR1                       : ok=1    changed=1    unreachable=0    failed=0    skipped=0    rescued=0    ignored=0

Fantastic, my nexus have been configured !! With the command show accounting log, you can verify the command injected by ansible. In my playbook, I added the line save_when: modified to save the configuration after the changes.

AGR1# show accounting log | last 10
Sat Mar 21 18:45:42 2020:type=stop:id=10.0.100.150@pts/2:user=ansible:cmd=shell terminated because the ssh session closed
Sat Mar 21 18:49:11 2020:type=start:id=10.0.100.150@pts/2:user=ansible:cmd=
Sat Mar 21 18:49:12 2020:type=update:id=10.0.100.150@pts/2:user=ansible:cmd=terminal length 0 (SUCCESS)
Sat Mar 21 18:49:12 2020:type=update:id=10.0.100.150@pts/2:user=ansible:cmd=terminal width 511 (SUCCESS)
Sat Mar 21 18:49:20 2020:type=update:id=10.0.100.150@pts/2:user=ansible:cmd=configure terminal ; hostname AGR1 (SUCCESS)
Sat Mar 21 18:49:26 2020:type=update:id=10.0.100.150@pts/2:user=ansible:cmd=Performing configuration copy.
Sat Mar 21 18:49:36 2020:type=start:id=vsh.bin.13650:user=admin:cmd=
Sat Mar 21 18:49:52 2020:type=update:id=10.0.100.150@pts/2:user=ansible:cmd=copy running-config startup-config (SUCCESS)
Sat Mar 21 18:49:53 2020:type=stop:id=10.0.100.150@pts/2:user=ansible:cmd=shell terminated because the ssh session closed
Sat Mar 21 18:52:35 2020:type=update:id=console0:user=admin:cmd=terminal width 511 (SUCCESS)

Now you can imagine the next step. You can add your syslog server for example.

    - name: configure syslog server
      nxos_config:
        lines:
          - logging server 10.0.100.42 4 use-vrf management facility local7
          - logging timestamp milliseconds
        save_when: modified

Before the change:

AGR1(config)# logging timestamp milliseconds ^C
AGR1(config)# sh logging 

Logging console:                enabled (Severity: critical)
Logging monitor:                enabled (Severity: notifications)
Logging linecard:               enabled (Severity: notifications)
Logging timestamp:              Seconds
Logging source-interface :      disabled
Logging rate-limit:             enabled
Logging server:                 disabled
Logging origin_id :             disabled
Logging RFC :                   disabled
Logging logflash:               enabled (Severity: notifications)
Logging logfile:                enabled
        Name - messages: Severity - notifications Size - 4194304

[..]

After the change:

AGR1(config)# 2020 Mar 21 18:58:48 AGR1 %$ VDC-1 %$  %SYSLOG-2-SYSTEM_MSG: Attempt to configure logging server with: hostname/IP 10.0.100.42,severity 4,port 514,facility local7 - syslogd
AGR1(config)# sh logging 

Logging console:                enabled (Severity: critical)
Logging monitor:                enabled (Severity: notifications)
Logging linecard:               enabled (Severity: notifications)
Logging timestamp:              Milliseconds
Logging source-interface :      disabled
Logging rate-limit:             enabled
Logging server:                 enabled
{10.0.100.42}
        This server is temporarily unreachable
        server severity:        warnings
        server facility:        local7
        server VRF:             management
        server port:            514
Logging origin_id :             disabled
Logging RFC :                   disabled
Logging logflash:               enabled (Severity: notifications)
Logging logfile:                enabled
        Name - messages: Severity - notifications Size - 4194304
[..]
root@09cf326cc275:/ansible/NXOS# ansible-playbook -i inventory-home playbook-home.yaml

PLAY [Setup Nexus Devices] ***********************************************************************************************************************

TASK [configure hostname] ************************************************************************************************************************

ok: [ACC1]
ok: [AGR1]
ok: [ACC2]

TASK [configure syslog server] *******************************************************************************************************************
changed: [ACC1]
changed: [ACC2]
changed: [AGR1]

PLAY RECAP ***************************************************************************************************************************************
ACC1                       : ok=2    changed=1    unreachable=0    failed=0    skipped=0    rescued=0    ignored=0   
ACC2                       : ok=2    changed=1    unreachable=0    failed=0    skipped=0    rescued=0    ignored=0   
AGR1                       : ok=2    changed=1    unreachable=0    failed=0    skipped=0    rescued=0    ignored=0

I can be useful to manage your access-list. Imagine you install a new server for the monitoring and you need to update one entry. This time we will use another module named nxos_acl.

    - name: configure SNMP-ACCESS-LIST
      nxos_acl:
        name: ACL_SNMP-ReadOnly
        seq: "10"
        action: permit
        proto: udp
        src: 10.0.100.42/32
        dest: any
        state: present

Now we have the ACL configured on all switches. When the module exists, prefer to use the specific module.

root@09cf326cc275:/ansible/NXOS# ansible-playbook -i inventory-home playbook-home.yaml

PLAY [Setup Nexus Devices] ***********************************************************************************************************************

TASK [configure hostname] ************************************************************************************************************************

ok: [ACC1]
ok: [AGR1]
ok: [ACC2]

TASK [configure syslog server] *******************************************************************************************************************
changed: [ACC1]
changed: [ACC2]
changed: [AGR1]

TASK [configure SNMP-ACCESS-LIST] ****************************************************************************************************************
changed: [ACC1]
changed: [ACC2]
changed: [AGR1]

PLAY RECAP ***************************************************************************************************************************************
ACC1                       : ok=3    changed=2    unreachable=0    failed=0    skipped=0    rescued=0    ignored=0   
ACC2                       : ok=3    changed=2    unreachable=0    failed=0    skipped=0    rescued=0    ignored=0   
AGR1                       : ok=3    changed=2    unreachable=0    failed=0    skipped=0    rescued=0    ignored=0 
AGR1(config)# sh ip access-lists ACL_SNMP-ReadOnly

IP access list ACL_SNMP-ReadOnly
        10 permit udp 10.0.100.42/32 any
--
ACC1(config)# sh ip access-lists ACL_SNMP-ReadOnly

IP access list ACL_SNMP-ReadOnly
	10 permit udp 10.0.100.42/32 any
--
ACC2# sh ip access-lists ACL_SNMP-ReadOnly

IP access list ACL_SNMP-ReadOnly
        10 permit udp 10.0.100.42/32 any 

This module is idempotent. Now we will update the ACL with a second entry. The documentation is here.

    - name: configure SNMP-ACCESS-LIST
      nxos_acl:
        name: ACL_SNMP-ReadOnly
        seq: "10"
        action: permit
        proto: udp
        src: 10.0.100.42/32
        dest: any
        state: present

    - name: configure SNMP-ACCESS-LIST
      nxos_acl:
        name: ACL_SNMP-ReadOnly
        seq: "20"
        action: permit
        proto: udp
        src: 10.0.100.43/32
        dest: any
        state: present
root@09cf326cc275:/ansible/NXOS# ansible-playbook -i inventory-home playbook-home.yaml

PLAY [Setup Nexus Devices] ***********************************************************************************************************************

TASK [configure hostname] ************************************************************************************************************************
changed: [ACC1]
changed: [AGR1]
changed: [ACC2]

TASK [configure syslog server] *******************************************************************************************************************
changed: [ACC1]
changed: [ACC2]
changed: [AGR1]

TASK [configure SNMP-ACCESS-LIST] ****************************************************************************************************************
ok: [ACC1]
ok: [AGR1]
ok: [ACC2]

TASK [configure SNMP-ACCESS-LIST] ****************************************************************************************************************
changed: [ACC1]
changed: [AGR1]
changed: [ACC2]

PLAY RECAP ***************************************************************************************************************************************
ACC1                       : ok=4    changed=3    unreachable=0    failed=0    skipped=0    rescued=0    ignored=0   
ACC2                       : ok=4    changed=3    unreachable=0    failed=0    skipped=0    rescued=0    ignored=0   
AGR1                       : ok=4    changed=3    unreachable=0    failed=0    skipped=0    rescued=0    ignored=0
AGR1(config)# sh ip access-lists ACL_SNMP-ReadOnly

IP access list ACL_SNMP-ReadOnly
        10 permit udp 10.0.100.42/32 any 
        20 permit udp 10.0.100.43/32 any

and they update the last entry with a new IP address.

    - name: configure SNMP-ACCESS-LIST
      nxos_acl:
        name: ACL_SNMP-ReadOnly
        seq: "10"
        action: permit
        proto: udp
        src: 10.0.100.42/32
        dest: any
        state: present

    - name: configure SNMP-ACCESS-LIST
      nxos_acl:
        name: ACL_SNMP-ReadOnly
        seq: "20"
        action: permit
        proto: udp
        src: 10.0.100.44/32
        dest: any
        state: present
root@09cf326cc275:/ansible/NXOS# ansible-playbook -i inventory-home playbook-home.yaml

PLAY [Setup Nexus Devices] ***********************************************************************************************************************

TASK [configure hostname] ************************************************************************************************************************
changed: [ACC1]
changed: [ACC2]
changed: [AGR1]

TASK [configure syslog server] *******************************************************************************************************************
changed: [ACC1]
changed: [AGR1]
changed: [ACC2]

TASK [configure SNMP-ACCESS-LIST] ****************************************************************************************************************
ok: [ACC1]
ok: [AGR1]
ok: [ACC2]

TASK [configure SNMP-ACCESS-LIST] ****************************************************************************************************************
changed: [ACC1]
changed: [AGR1]
changed: [ACC2]

PLAY RECAP ***************************************************************************************************************************************
ACC1                       : ok=4    changed=3    unreachable=0    failed=0    skipped=0    rescued=0    ignored=0   
ACC2                       : ok=4    changed=3    unreachable=0    failed=0    skipped=0    rescued=0    ignored=0   
AGR1                       : ok=4    changed=3    unreachable=0    failed=0    skipped=0    rescued=0    ignored=0 
AGR1(config)# sh ip access-lists ACL_SNMP-ReadOnly

IP access list ACL_SNMP-ReadOnly
        10 permit udp 10.0.100.42/32 any 
        20 permit udp 10.0.100.44/32 any

You can image a lot of scenario now, and apply your change very quickly.