DNS Woes

shawndoyle · 2016-08-19T17:31:08.000Z

So here’s the deal. We have this strange issue that’s cropped up. We have two buildings. One of Which works perfectly fine. The other is having some sort of issue “we believe” with dns. The way it presents is that the user will turn on their pc and it will boot up normally but it will not have any access to Outlook, Lync or Network Shares. Under network Connectivity it will show that it’s connected to our intranet but no Internet access.

If left alone it will work in approximately 15 MINUTES. Till we fix the problem we have advised our users to keep rebooting until they get a connection. That will usually resolve the problem in 2-3 reboots. Understandably this is frustrating our users.

My Feeling is that on some level that DNS is flaking out. In the testing we have done while the issue is going on we have been able to successfully ping using the ip address but not the hostname. I am authenticated on our domain and we tested that by going to \ip.address\c$ and i was able to successfully browse there.

So i created a script to try and help identify the problem. I am new to powershell so please forgive the code.

## original author https://community.spiceworks.com/people/martin9700
$Count = 5
$Ping = @()
$Computer = "usmfgflofil01";
While ($Count -gt 0)
## help about_assignment_operators
{   $Ping += Get-WmiObject Win32_PingStatus -Filter "Address = '$Computer'" | Select @{Label="TimeStamp";Expression={Get-Date}},@{Label="Source";Expression={ $_.__Server }},@{Label="Destination";Expression={ $_.Address }},IPv4Address,@{Label="Status";Expression={ If ($_.StatusCode -ne 0) {"Failed"} Else {""}}},ResponseTime
    $Count --
    Start-Sleep -Seconds 1
}
$Ping | Select TimeStamp,Source,Destination,IPv4Address,Status,ResponseTime | ft -AutoSize
$Ping | Select TimeStamp,Source,Destination,IPv4Address,Status,ResponseTime | Export-CSV c:\DNS-Testing\$env:COMPUTERNAME.pinglog.csv -NoTypeInformation -Append

##Get all of the running services
Get-Service | Select-Object -Property Name,DisplayName,Status | Sort-Object status | Format-Table -AutoSize  
Get-Service | Select-Object -Property Name,DisplayName,Status | export-csv -Delimiter "|" -path "C:\DNS-Testing\$env:COMPUTERNAME.services.csv" -NoTypeInformation -Append

#Get a list of all the running Proccesses
Get-Process | Select-Object -Property ProcessName,Description, Responding | Sort-Object Processname | Format-Table -AutoSize
Get-Process | Select-Object -Property ProcessName,Description,Responding | Sort-Object name | Export-Csv -Delimiter "|" -Path C:\DNS-Testing\$env:COMPUTERNAME.processes.csv -NoTypeInformation -Append

## Test-Connection -Source usmfgflolapsd1 -ComputerName "localhost" , "usmfgflofil01"  , "usmfgflofil03" , "usnadcflo01"   ,  "usnadcgat0264b"  | Select-Object -Property Pscomputername,Ipv4address,Address | Format-Table -AutoSize
## Test-Connection -Source usmfgflolapsd1 -ComputerName "localhost" , "usmfgflofil01"  , "usmfgflofil03" , "usnadcflo01"   ,  "usnadcgat0264b"  | Select-Object -Property Pscomputername,Ipv4address,Address | Export-Csv -Delimiter "|" -Path "C:\DNS-Testing\$env:computername.Pinglog-byname.csv"

## Test-Connection -Source usmfgflolapsd1 -ComputerName "127.0.0.1" , "128.202.105.148", "161.241.111.4" , "161.241.111.12",  "128.200.96.195"  | Select-Object -Property Pscomputername,Ipv4address,Address | Format-Table -AutoSize
## Test-Connection -Source usmfgflolapsd1 -ComputerName "127.0.0.1" , "128.202.105.148", "161.241.111.4" , "161.241.111.12",  "128.200.96.195"  | Select-Object -Property Pscomputername,Ipv4address,Address | Export-Csv -Delimiter "|" -Path "C:\DNS-Testing\$env:computername.Pinglog-ByIP.csv"

What i am trying to do is to modify the existing code to be able to ping multiple servers during testing. Because as the code is written now i do not understand how.

Any help in this area would be appreciated.

guillermovargas · 2016-08-19T17:36:21.000Z

Have you properly configured the DNS servers (on the machines having the issue)? If yes, is NAT setup properly on your firewall/router?

sactownchad · 2016-08-19T18:10:33.000Z

So DNS is pretty simple… The DNS server either needs to know about resources (Authoritative) or it will help find them (Forwarding.) Internal DNS like what is found on Domain controllers is usually configured to know about domain resources and will forward to the internet when it can’t find what it is looking for. External DNS servers out on the internet are unaware of local resources such as domain joined computers etc.

With that said, many network and systems admins still insist on pointing systems to external DNS servers, usually as secondary or tertiary servers thinking “Well if my local DNS servers go down, at least we can still get on the internet” not understanding that secondary and tertiary servers are often used for lookups even if the primary is up. What happens then is systems can reach the internet fine but will occasionally not be able to resolve local resources such as servers, printers and other workstations.
Make sure that internal systems only point to internal DNS.

Rob-Dunn · 2016-08-19T23:55:17.000Z

Yes ^ this. The other thing about the primary, secondary, tertiary DNS servers in Windows is that as long as the client DNS gets a proper response (i.e. a response on port 53), the client will never check the secondary or tertiary servers. This is a Windows thing. It’s kinda dumb, but that’s the way it is.

Check DHCP scope settings; or if they’re static addresses, look at the primary/secondary DNS servers at the client level (on the NIC properties). In typical domain environments, the domain controllers also serve as your DNS servers for AD. So, your client NIC properties should point to one (or both, etc.) of your domain controllers. Next, you need to make sure that whatever primary DNS server your clients are pointing to, that DNS server should have forwarders configured (i.e. “where to look when it can’t resolve DNS addresses internally” - this could be configured to point to Google at 8.8.8.8/8.8.4.4, OpenDNS, Comcast, or your local ISP).

Also, to help facilitate a healthy AD environment and internal DNS in general - - take a look at this. Assuming your DCs are also your DNS servers (let’s assume you have three):

Server 1 IP: 192.168.0.1

Primary DNS: 192.168.0.2
Secondary DNS: 192.168.0.3
Tertiary DNS: 127.0.0.1

Server 2 IP: 192.168.0.2

Primary DNS: 192.168.0.3
Secondary DNS: 192.168.0.1
Tertiary DNS: 127.0.0.1

Server 3 IP: 192.168.0.3

Primary DNS: 192.168.0.1
Secondary DNS: 192.168.0.2
Tertiary DNS: 127.0.0.1

Configure forwarders on each of them to ensure that you don’t have an interruption in external Internet access.

markmckinlay · 2016-08-22T06:12:07.000Z

When you try to ping by name are you using FQDN or just the short name? If it works with FQDN but not the short then its likely a DHCP issue and it isnt setting the primary DNS suffix.

shawndoyle · 2016-08-22T15:32:11.000Z

So a couple of things. First i would like to point out that i am a IT Analyst at my company and unfortunately The Domain Controller is out of the scope of what i have access too. So, im starting to think that this should be resolved more at a corporate level.

Mark McKinlay:

When you try to ping by name are you using FQDN or just the short name? If it works with FQDN but not the short then its likely a DHCP issue and it isnt setting the primary DNS suffix.

Mark,

We have tried both the short name and the FQDN both having the same response.

Rob,

I Checked client NIC properties and they do point to or both of our domain controllers.

davidgpaul · 2016-08-22T18:23:42.000Z

shawndoyle:

So a couple of things. First i would like to point out that i am a IT Analyst at my company and unfortunately The Domain Controller is out of the scope of what i have access too. So, im starting to think that this should be resolved more at a corporate level.

Mark McKinlay:

When you try to ping by name are you using FQDN or just the short name? If it works with FQDN but not the short then its likely a DHCP issue and it isnt setting the primary DNS suffix.

Mark,

We have tried both the short name and the FQDN both having the same response.

Rob,

I Checked client NIC properties and they do point to or both of our domain controllers.

Can you ping those two DCs right away on the affected machine after login when this issue is present?

Rob-Dunn · 2016-08-22T18:27:03.000Z

I’d be willing to bet there is some goofy DNS and AD replication going on in the background. The server admins need to take a look at that and ensure all is well on the backend.

shawndoyle · 2016-08-23T10:21:34.000Z

We have our networking team looking into it but as of yet nothing to report. I will keep you guys posted. But going back to the original post i was more hoping for some powershell coding pointers to get some help with that portion of it.

"What i am trying to do is to modify the existing code to be able to ping multiple servers during testing "

Can someone please help me with that?

gungnir · 2016-08-23T10:42:56.000Z

shawndoyle:

But going back to the original post i was more hoping for some powershell coding pointers to get some help with that portion of it.

“What i am trying to do is to modify the existing code to be able to ping multiple servers during testing”

Can someone please help me with that?

Something like this should be able to accomplish that.

$Count = 5
$Computers = @(
    'Target1'
    'Target2'
    'Target3'
    )

$Ping = While ($Count -gt 0){
    foreach( $Computer in $Computers ){
        Get-WmiObject Win32_PingStatus -Filter "Address = '$Computer'" |
            Select @{Label="TimeStamp";Expression={Get-Date}},@{Label="Source";Expression={ $_.__Server }},@{Label="Destination";Expression={ $_.Address }},IPv4Address,@{Label="Status";Expression={ If ($_.StatusCode -ne 0) {"Failed"} Else {""}}},ResponseTime
        }

    $Count --
    Start-Sleep -Seconds 1
    }

$Ping |
    Select-Object -Property Destination,TimeStamp,Source,IPv4Address,Status,ResponseTime |
    Sort-Object -Property Destination, TimeStamp |
    Format-Table -AutoSize

$Ping |
    Select-Object -Property Destination,TimeStamp,Source,IPv4Address,Status,ResponseTime |
    Sort-Object -Property Destination, TimeStamp |
    Export-CSV c:\DNS-Testing\$env:COMPUTERNAME.pinglog.csv -NoTypeInformation -Append

gungnir · 2016-08-23T10:58:58.000Z

Gungnir:

shawndoyle:

But going back to the original post i was more hoping for some powershell coding pointers to get some help with that portion of it.

“What i am trying to do is to modify the existing code to be able to ping multiple servers during testing”

Can someone please help me with that?

Something like this should be able to accomplish that.
...

I didn’t like how messy the select statement looked in the foreach loop, so I switched it to something a bit cleaner ( at least to my eye ). Also removed a couple of redundant Select-Object’s.

This one requires at least version 3 of PowerShell, however.

$Count = 5
$Computers = @(
    'Target1'
    'Target2'
    'Target3'
    )

$Ping = While ($Count -gt 0){
    foreach( $Computer in $Computers ){
        $Response = Get-WmiObject Win32_PingStatus -Filter "Address = '$Computer'"
        
        [pscustomobject]@{
            Destination  = $Response.Address
            Timestamp    = Get-Date
            Source       = $Response.__Server
            IPv4Address  = $Response.IPv4Address
            Status       = if( $Response.StatusCode -ne 0 ){ 'Failed' } else { '' }
            ResponseTime = $Response.ResponseTime
            }
        }

    $Count --
    Start-Sleep -Seconds 1
    }

$Ping |
    Sort-Object -Property Destination, Timestamp |
    Format-Table -AutoSize

$Ping |
    Sort-Object -Property Destination, Timestamp |
    Export-CSV c:\DNS-Testing\$env:COMPUTERNAME.pinglog.csv -NoTypeInformation -Append

Rob-Dunn · 2016-08-23T11:03:57.000Z

Gungnir:

Gungnir:
shawndoyle:

But going back to the original post i was more hoping for some powershell coding pointers to get some help with that portion of it.

“What i am trying to do is to modify the existing code to be able to ping multiple servers during testing”

Can someone please help me with that?

Something like this should be able to accomplish that.
...
I didn’t like how messy the select statement looked in the foreach loop, so I switched it to something a bit cleaner ( at least to my eye ). Also removed a couple of redundant Select-Object’s.

This one requires at least version 3 of PowerShell, however.
$Count = 5
$Computers = @(
    'Target1'
    'Target2'
    'Target3'
    )

$Ping = While ($Count -gt 0){
    foreach( $Computer in $Computers ){
        $Response = Get-WmiObject Win32_PingStatus -Filter "Address = '$Computer'"
        
        [pscustomobject]@{
            Destination  = $Response.Address
            Timestamp    = Get-Date
            Source       = $Response.__Server
            IPv4Address  = $Response.IPv4Address
            Status       = if( $Response.StatusCode -ne 0 ){ 'Failed' } else { '' }
            ResponseTime = $Response.ResponseTime
            }
        }

    $Count --
    Start-Sleep -Seconds 1
    }

$Ping |
    Sort-Object -Property Destination, Timestamp |
    Format-Table -AutoSize

$Ping |
    Sort-Object -Property Destination, Timestamp |
    Export-CSV c:\DNS-Testing\$env:COMPUTERNAME.pinglog.csv -NoTypeInformation -Append

I always like to add this sort of thing at the top of my scripts if I know it requires a certain version of PowerShell:

#requires -version 3

Not sure if you were aware of that or not!

gungnir · 2016-08-23T11:10:54.000Z

Rob Dunn:

Gungnir:
Gungnir:
shawndoyle:

But going back to the original post i was more hoping for some powershell coding pointers to get some help with that portion of it.

“What i am trying to do is to modify the existing code to be able to ping multiple servers during testing”

Can someone please help me with that?

Something like this should be able to accomplish that.
...
I didn’t like how messy the select statement looked in the foreach loop, so I switched it to something a bit cleaner ( at least to my eye ). Also removed a couple of redundant Select-Object’s.

This one requires at least version 3 of PowerShell, however.
$Count = 5
$Computers = @(
    'Target1'
    'Target2'
    'Target3'
    )

$Ping = While ($Count -gt 0){
    foreach( $Computer in $Computers ){
        $Response = Get-WmiObject Win32_PingStatus -Filter "Address = '$Computer'"
        
        [pscustomobject]@{
            Destination  = $Response.Address
            Timestamp    = Get-Date
            Source       = $Response.__Server
            IPv4Address  = $Response.IPv4Address
            Status       = if( $Response.StatusCode -ne 0 ){ 'Failed' } else { '' }
            ResponseTime = $Response.ResponseTime
            }
        }

    $Count --
    Start-Sleep -Seconds 1
    }

$Ping |
    Sort-Object -Property Destination, Timestamp |
    Format-Table -AutoSize

$Ping |
    Sort-Object -Property Destination, Timestamp |
    Export-CSV c:\DNS-Testing\$env:COMPUTERNAME.pinglog.csv -NoTypeInformation -Append
I always like to add this sort of thing at the top of my scripts if I know it requires a certain version of PowerShell:
#requires -version 3
Not sure if you were aware of that or not!

I knew about it, but it always slips my mind ( I’m lucky when I remember to mention that a script needs at least v3 ). All our computers here are on version 4 or 5, so its not something I usually need to use.