How can Ansible assist individuals constructing simulations with Cisco Modeling Labs (CML)?

Much like Terraform, Ansible is a standard, open-source automation device typically utilized in Steady Integration/Steady Deployment (CI/CD) DevOps methodologies. They’re each a sort of Infrastructure as Code (IaC) or Infrastructure as Information that assist you to render your infrastructure as textual content recordsdata and management it utilizing instruments reminiscent of Git. The benefit is reproducibility, consistency, velocity, and the data that, once you change the code, individuals approve, and it will get examined earlier than it’s pushed out to your manufacturing community. This paradigm permits enterprises to run their community infrastructure in the identical approach they run their software program and cloud practices. Afterall, the infrastructure is there to assist the apps, so why handle them in a different way? 

Though overlaps exist within the capabilities of Terraform and Ansible, they’re very complementary. Whereas Terraform is best on the preliminary deployment and making certain ongoing consistency of the underlying infrastructure, Ansible is best on the preliminary configuration and ongoing administration of the issues that reside in that infrastructure, reminiscent of techniques, community units, and so forth. 

In a standard workflow wherein an operator desires to make a change to the community, let’s say including a brand new community to be marketed through BGP, a community engineer would specify that change within the code or extra doubtless as configuration knowledge in YAML or JSON. In a typical CI workflow, that change would have to be authorised by others for correctness or adherence to company and safety issues, as an illustration. Along with the eyeball assessments, a collection of automated testing validates the info after which deploys the proposed change in a take a look at community. These assessments might be run in a bodily take a look at community, a digital take a look at community, or a mix of the 2. That circulation would possibly seem like the next: 

The benefit of leveraging digital take a look at networks is profound. The price is dramatically decrease, and the power to automate testing is elevated considerably. For instance, a community engineer can spin up and configure a brand new, complicated topology a number of instances with out the chance of outdated assessments messing up the accuracy of the present testing. Cisco Modeling Labs is a superb device for any such take a look at. 

Right here’s the place the Ansible CML Assortment is available in. Much like the CML Terraform integration coated in a earlier weblog, the Ansible CML Assortment can automate the deployment of topologies in CML for testing. The Ansible CML Assortment has modules to create, begin, and cease a topology and the hosts inside it, however extra importantly, it has a dynamic stock plugin for getting details about the topology. That is essential for automation as a result of topologies can change. Or a number of topologies might exist, relying on the assessments being carried out. In case your topology makes use of dynamic host configuration protocol (DHCP) and/or CML’s PATty performance, the knowledge for a way Ansible communicates with the nodes must be communicated to the playbook. 

Let’s go over among the options of the Ansible CML Assortment’s dynamic stock plugin. 

First, we have to set up the gathering: 

ansible-galaxy assortment set up cisco.cml 

Subsequent, we create a cml.yml within the stock with the next contents to inform Ansible to make use of the Ansible CML Assortment’s dynamic stock plugin: 

plugin: cisco.cml.cml_inventory 

group_tags: community, ios, nxos, router

As well as to specifying the plugin identify, we will additionally outline tags that, when discovered on the units within the topology, add that machine to an Ansible group for use later within the playbook: 

As well as to specifying the plugin identify, we will additionally outline tags that, when discovered on the units within the topology, add that machine to an Ansible group for use later within the playbook:

• CML_USERNAME: Username for the CML consumer
• CML_PASSWORD: Password for the CML consumer
• CML_HOST: The CML host
• CML_LAB: The identify of the lab 

As soon as the plugin is aware of how one can talk with the CML server and which lab to make use of, it might probably return details about the nodes within the lab: 

okay: [hq-rtr1] => { 

    "cml_facts": { 

        "config": "hostname hq-rtr1nvrf definition Mgmt-intfn!naddress-family ipv4nexit-address-familyn!naddress-family ipv6nexit-address-familyn!nusername admin privilege 15 secret 0 adminncdp runnno aaa new-modelnip domain-name mdd.cisco.comn!ninterface GigabitEthernet1nvrf forwarding Mgmt-intfnip tackle dhcpnnegotiation autonno cdp enablenno shutdownn!ninterface GigabitEthernet2ncdp enablen!ninterface GigabitEthernet3ncdp enablen!ninterface GigabitEthernet4ncdp enablen!nip http servernip http secure-servernip http max-connections 2n!nip ssh time-out 60nip ssh model 2nip ssh server algorithm encryption aes128-ctr aes192-ctr aes256-ctrnip ssh shopper algorithm encryption aes128-ctr aes192-ctr aes256-ctrn!nline vty 0 4nexec-timeout 30 0nabsolute-timeout 60nsession-limit 16nlogin localntransport enter sshn!nend", 

        "cpus": 1, 

        "data_volume": null, 

        "image_definition": null, 

        "interfaces": [ 

            { 

                "ipv4_addresses": null, 

                "ipv6_addresses": null, 

                "mac_address": null, 

                "name": "Loopback0", 

                "state": "STARTED" 

            }, 

            { 

                "ipv4_addresses": [ 

                    "192.168.255.199" 

                ], 

                "ipv6_addresses": [], 

                "mac_address": "52:54:00:13:51:66", 

                "identify": "GigabitEthernet1", 

                "state": "STARTED" 

            } 

        ], 

        "node_definition": "csr1000v", 

        "ram": 3072, 

        "state": "BOOTED" 

    } 

} 

The primary IPv4 tackle discovered (so as of the interfaces) is used as `ansible_host` to allow the playbook to connect with the machine. We will use the cisco.cml.stock playbook included within the assortment to point out the stock. On this case, we solely specify that we would like units which can be within the “router” group created by the stock plugin as knowledgeable by the tags on the units: 

mdd % ansible-playbook cisco.cml.stock --limit=router 

okay: [hq-rtr1] => { 

    "msg": "Node: hq-rtr1(csr1000v), State: BOOTED, Deal with: 192.168.255.199:22" 

} 

okay: [hq-rtr2] => { 

    "msg": "Node: hq-rtr2(csr1000v), State: BOOTED, Deal with: 192.168.255.53:22" 

} 

okay: [site1-rtr1] => { 

    "msg": "Node: site1-rtr1(csr1000v), State: BOOTED, Deal with: 192.168.255.63:22" 

} 

okay: [site2-rtr1] => { 

    "msg": "Node: site2-rtr1(csr1000v), State: BOOTED, Deal with: 192.168.255.7:22" 

} 

Along with group tags, the CML dynamic stock plugin may even parse tags to cross data from PATty and to create generic stock information: 

If a CML tag is specified that matches `^pat:(?:tcp|udp)?:?(d+):(d+)`, the CML server tackle (versus the primary IPv4 tackle discovered) shall be used for `ansible_host`. To vary `ansible_port` to level to the translated SSH port, the tag `ansible:ansible_port=2020` might be set. These two tags inform the Ansible playbook to connect with port 2020 of the CML server to automate the required host within the topology. The `ansible:` tag can be used to specify different host information. For instance, the tag `ansible:nso_api_port=2021` can be utilized to inform the playbook the port to make use of to achieve the Cisco NSO API. Any arbitrary truth might be set on this approach. 

Getting began 

Making an attempt out the CML Ansible Assortment is straightforward. You need to use the playbooks offered within the assortment to load and begin a topology in your CML server. To begin, outline the surroundings variable that tells the gathering how one can entry your CML server: 

% export CML_HOST=my-cml-server.my-domain.com 

% export CML_USERNAME=my-cml-username 

% export CML_PASSWORD=my-cml-password 

The following step is to outline your topology file. That is a commonplace topology file you can export from CML. There are two methods to outline the topology file. First, you’ll be able to use  an surroundings variable: 

% export CML_LAB=my-cml-labfile 

Alternatively, you’ll be able to specify the topology file once you run the playbook as an additional–var.  For instance, to spin up a topology utilizing the in-built cisco.cml.construct playbook: 

% ansible-playbook cisco.cml.construct -e wait="sure" -e  

This command hundreds and begins the topology; then it waits till all nodes are working to finish.  If -e startup=’host’ is specified, the playbook will begin every host individually versus beginning them all of sudden.  This enables for the config to be generated and fed into the host on startup.  When cml_config_file is outlined within the host’s stock, it’s parsed as a Jinja file and fed into that host as config at startup.  This enables for just-in-time configuration to happen. 

As soon as the playbook completes, you should utilize one other built-in playbook, cisco.cml.stock, to get the stock for the topology.  With the intention to use it, first create a cml.yml within the stock listing as proven above, then run the playbook as follows: 

% ansible-playbook cisco.cml.stock 

PLAY [cml_hosts] ********************************************************************** 

TASK [debug] ********************************************************************** 

okay: [WAN-rtr1] => { 

    "msg": "Node: WAN-rtr1(csr1000v), State: BOOTED, Deal with: 192.168.255.53:22" 

} 

okay: [nso1] => { 

    "msg": "Node: nso1(ubuntu), State: BOOTED, Deal with: my-cml-server.my-domain.com:2010" 

} 

okay: [site1-host1] => { 

    "msg": "Node: site1-host1(ubuntu), State: BOOTED, Deal with: site1-host1:22" 

} 

On this truncated output, three totally different situations are proven.  First, WAN-rtr1 is assigned the DHCP tackle it obtained for its ansible_host worth, and ansible port is 22. If the host working the playbook has IP connectivity (both within the topology or a community related to the topology with an exterior connector), will probably be in a position to attain that host. 

The second situation exhibits an instance of the PATty performance with the host nso1 wherein the dynamic stock plugin reads these tags to find out that the host is obtainable via the CML server’s interface (i.e. ansible_host is about to my-cml-server.my-domain.com).  Additionally, it is aware of that ansible_port needs to be set to the port specified within the tags (i.e. 2010).  After these values are set, the ansible playbook can attain the host within the topology utilizing the PATty performance in CML. 

The final instance, site1-host1, exhibits the situation wherein the CML dynamic stock script can both discover a DHCP allotted tackle or tags to specify to what ansible_host needs to be set, so it makes use of the node identify.  For the playbook to achieve these hosts, it must have IP connectivity and be capable to resolve the node identify to an IP tackle. 

These built-in playbooks present examples of how one can use the performance within the CML Ansible Assortment to construct your individual playbooks, however you can too use them straight as a part of your pipeline.  In truth, we regularly use them straight within the pipelines we construct for purchasers. 

If you wish to be taught extra in regards to the CML Ansible Assortment, you could find it in Ansible Galaxy in addition to on Github. 

You can even discover a full, IaC CI/CD pipeline utilizing these modules right here.

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