README.md

Startup configuration

This exercise demonstrates how to provide startup configuration to the lab nodes by means of the startup-config node parameter in the topology file.

Startup configuration is a way to provide initial configuration to the lab nodes when they boot up. This is useful when you want to automate the configuration of the nodes and avoid manual intervention. It also brings your lab to a desired state when you need to test a specific scenario.

To enter the lab directory, run the following command from anywhere in your terminal:

cd ~/ac2-clab/15-startup/

We start by deploying a lab defined in the startup.clab.yml topology file. The lab consists of two nodes: srl (Nokia SR Linux) and ceos (Arista cEOS). Both nodes are configured with a startup configuration file that resides in the same directory as the topology file.

We will use the shortened syntax when deploying the lab; less typing and more fun!

sudo clab dep -c

Note, that when calling clab dep -c the containerlab will try to find the *.clab.yml file in the current working directory. If the file is located elsewhere, you can specify the path to the file as an argument to the clab dep command.
The -c flag stands for --cleanup and it will ensure that if the lab is already running, it will be stopped and removed before deploying a new one.

The startup configuration files - srl.cfg and ceos.cfg - configure the interfaces, IP addressing, loopbacks and BGP peering between SR Linux and cEOS nodes respectively.

In particular, the srl node is configured to announce its loopback address 10.10.10.1/32 towards the ceos node and the ceos node is configured to announce its loopback address 10.10.10.2/32 towards the srl node.

After the lab is deployed, we can expect that the nodes will boot up and apply the startup configuration snippets provided in the topology file. Consequently, it is fair to assume that the nodes will establish BGP peering and exchange routes.

Let's connect to the clab-startup-srl node and check the BGP peering status:

ssh clab-startup-srl

show network-instance default protocols bgp neighbor 192.168.1.2

You should see 1 route sent/received for the above BGP neighbor.

------------------------------------------------------------------------------------------------------------------------------------------------------
BGP neighbor summary for network-instance "default"
Flags: S static, D dynamic, L discovered by LLDP, B BFD enabled, - disabled, * slow
------------------------------------------------------------------------------------------------------------------------------------------------------
------------------------------------------------------------------------------------------------------------------------------------------------------
+-----------------+------------------------+-----------------+------+---------+--------------+--------------+------------+------------------------+
|    Net-Inst     |          Peer          |      Group      | Flag | Peer-AS |    State     |    Uptime    |  AFI/SAFI  |     [Rx/Active/Tx]     |
|                 |                        |                 |  s   |         |              |              |            |                        |
+=================+========================+=================+======+=========+==============+==============+============+========================+
| default         | 192.168.1.2            | ibgp            | S    | 65001   | established  | 0d:0h:1m:56s | ipv4-      | [1/1/1]                |
|                 |                        |                 |      |         |              |              | unicast    |                        |
+-----------------+------------------------+-----------------+------+---------+--------------+--------------+------------+------------------------+
------------------------------------------------------------------------------------------------------------------------------------------------------
Summary:
1 configured neighbors, 1 configured sessions are established, 0 disabled peers
0 dynamic peers

Now, let's make sure that it can reach the loopback address announced by the ceos node.

When in the SRL CLI, issue a ping towards the ceos node's loopback address, we will need to use the default network interface instead of the mgmt:

ping network-instance default 10.10.10.2

You should see a successful ping response.

You have successfully deployed the lab with the nodes equipped with the startup configuration. This is a powerful feature that can be used to provision the nodes with the desired configuration when they boot up.