Posh-SSH script on Cisco devices

Question

I made a Posh-SSH based script that will let me send commands to Cisco routers. It works great... except for a very specific case.

function Send-SSHCommand {
        Param(
            [Parameter(Mandatory=$true)]
            [String]$Command,
            [Parameter(Mandatory=$false)]
            [string]$DeviceName = "CiscoRouter"
        )

            remove-variable Response -ErrorAction SilentlyContinue
            Get-SSHSession | select SessionId | Remove-SSHSession | Out-Null
            New-SSHSession -ComputerName $DeviceName -AcceptKey -Credential $Credential | Out-Null
            $session = Get-SSHSession -Index 0 
            $stream = $session.Session.CreateShellStream("dumb", 0, 0, 0, 0, 1000)

            $stream.Write("terminal Length 0`n")
            sleep -mill 60
            $stream.Read() | Out-Null
            $stream.Write("$Command`n")
            $ResponseRaw = $stream.Read()
            $Response = $ResponseRaw -split "`r`n" | %{$_.trim()}
            
            while (($Response[$Response.Count -1]) -ne "$DeviceName#") {
                
                sleep -mill 60
                $ResponseRaw = $stream.Read()
                $Response = $ResponseRaw -split "`r`n" | %{$_.trim()}

            }
            Return $Response
}

Usage Examples that work correctly:

Send-SSHCommand "sh ip cache flow" -DeviceName "CiscoRouter1"

Send-SSHCommand "sho ip int bri | include Serial|NVRAM|Multilink1|manual" -DeviceName "CiscoRouter1"

Send-SSHCommand "sho bgp sum" -DeviceName "CiscoRouter1"

However, the script will hang indefinitely when I use a command like below on any device that doesn't return a respective result for the command. The script is expecting a result. So, when its executed on a device that doesn't return any information for a command, the script just hangs indefinitely:

Send-SSHCommand "sh flow monitor" -DeviceName "CiscoRouter2"

This is what it looks like on a device's console that doesn't have a respective result for sho flow monitor:

CiscoRouter2#sh flow monitor
CiscoRouter2#

The script works perfectly in cases like below where there is information returned like below:

CiscoRouter1#sh flow monitor
Flow Monitor Traffic_INPUT:
Description:       DDR-FO NetFlow
Flow Record:       SER-INPUT
CiscoRouter1#

How can I write the while logic so it doesn't hang in cases where no information is returned from the command?

You could add a variable to your while loop that increments - while ((($Response[$Response.Count -1]) -ne "$DeviceName#") -and ($x -lt 100)) {$x++;sleep -mill 60; etc. Each loop takes approx 60ms so $x -lt 100 would exit after 6 seconds of waiting. — Mike Anthony, Apr 06 '22 at 02:10

Posh-SSH script on Cisco devices

0 Answers0