Infrastructure testing using Pester - Part 3

In this article, I will explain briefly about how to use Pester to validate your switching infrastructure/ switch configurations. If your switches have incorrect configurations, you will experience several problems like network disconnections, high latency, low throughput, etc. And all these will contribute towards network performance issues. In a hyper-converged infrastructure, incorrect switch configurations will affect both compute and storage performance. So it is very important to make sure your switches are configured in the right way according to best practice recommendations.

Using Pester tests, you can define the expected configuration rules and execute it against your existing switches to verify everything is configured correctly or not.

Here in this example, I will show how to verify the below.

• Networking OS version (here I am using Dell EMC S5048F-ON switch)
• The interfaces are Up (given a range)
• A given set of VLANs are present and Up

Prerequisite PowerShell modules:

• Pester - Version 4.3.1
• Posh-SSH - Version 2.0.2

Note: I am using Powershell 5.1.14393.0

#Collect input 

#Provide interface range to verify status

[int]$Start_port = Read-host "Enter starting switch port number"

[int]$End_port = Read-host "Enter ending switch port number"

#Provide VLANs to verify status

[int[]]$vlans = 20,23

$check_vlans = @{}

#New SSH session to the Switch 

$sw_creds = Get-Credential -Message "Enter switch creds"

Write-Host "Creating new SSH session to Switch."

$SWssh = New-SSHSession -ComputerName 192.168.10.4 -Credential $sw_creds -Force -ConnectionTimeout 300

Write-Host "Collecting configuration details from Switch. This will take few seconds."

Start-Sleep -s 3

Write-Host "Collecting VLAN details from Switch. This will take few seconds."

for ($j=0; $j -lt $vlans.Count; $j++) {

    Write-Host "Collecting details of VLAN $($vlans[$j])"

    $cmd_vlan = "show interfaces vlan $($vlans[$j])"

    $check_vlan = invoke-sshcommand -Command $cmd_vlan -SSHSession $SWssh

    Start-Sleep -s 3

    $check_vlans[$j] = $check_vlan.Output

}

#Collecting networking OS info 

$Networking_OS = Invoke-SSHCommand -SSHSession $SWssh -Command "show system"

Start-Sleep -s 3

#Collecting interface status details

$interface_cmd =  "show interfaces twentyFiveGigE 1/$Start_port-1/$End_port"

$interface_status = Invoke-SSHCommand -SSHSession $SWssh -Command $interface_cmd

Write-Host "Configuration verification started.`n"

Describe "System basic checks" {

    Context "Check networking OS version" {

        It "Should be Dell EMC Networking OS Version : 9.12(1.0)" {

            ($Networking_OS.Output) -match 'Dell EMC Networking OS Version : 9\.12\(1\.0\)\s\s$' | Should be $true

        }

    }

}

$Global:i=1

Describe "Interface checks" {

    for ($i=$Start_port; $i -le $End_port; $i++) {

        Context "Interface should be UP" {

            It "Interface 1/$i should be UP" {

                 $Global:c1 = "twentyFiveGigE 1/$i is up, line protocol is up"

                 $res = ($interface_status.Output) -match $c1

                 $res | should be $true

            }

        }

    }

}

Describe "VLAN checks" {

    for ($j=0; $j -lt $vlans.Count; $j++) {

        Context "Check VLAN $($vlans[$j])" {

             It "Should contain VLAN $($vlans[$j])" {

                  $check = ($check_vlans[$j]) -match '% Error: No such interface'

                  $check | should be $null

                  Write-host $check

             }

             It "VLAN $($vlans[$j]) should be UP" {

                  $tt = "Vlan $($vlans[$j]) is up, line protocol is up"

                  $t3 = ($check_vlans[$j]) -match $tt

                  $t3 | should be $true

             }

        }

    }

}

Remove-SSHSession -SSHSession $SWssh

#Sample output

You can write custom Pester tests according to your switching infrastructure configuration, where you can verify port channels, VLAN membership of switch ports, VLT configuration etc. Hope this was helpful. Cheers!