emrecavunt/wsl2.md

## wsl2.md

      
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              wsl2.md
            
          
    The problem

Err:1 http://archive.ubuntu.com/ubuntu focal InRelease
  Temporary failure resolving 'archive.ubuntu.com'


On wsl2 sudo apt update will fail when connected to Cisco Anyconnect VPN but without vpn it works fine. The problem is when you are connected to anyconnect, wsl fails to resolve the DNS.

The solution

Connect Cisco Anyconnect VPN, then open up powershell as Admin and run the following commands to get the all the available DNS/nameservers. Take note of the DNS/namservers will need later.
Get-DnsClientServerAddress -AddressFamily IPv4 | Select-Object -ExpandProperty ServerAddresses
Then on the same powershell run the following. This will get the search domain that will need later on with the nameservers above.
Get-DnsClientGlobalSetting | Select-Object -ExpandProperty SuffixSearchList
Open up wsl, and run the following commands.
On WSL (Ubuntu or any linux distro)
sudo unlink /etc/resolv.conf # this will unlink the default wsl2 resolv.conf

# This config will prevent wsl2 from overwritting the resolve.conf file everytime
# you start wsl2
cat <<EOF | sudo tee -a /etc/wsl.conf
[network]
generateResolvConf = false
EOF

cat <<EOF | sudo tee -a /etc/resolv.conf
nameserver 10.50... # The company DNS/nameserver from the command in step 1
nameserver 10.50... # The company DNS/nameserver from the command in step 1
nameserver 8.8.8.8
nameserver 8.8.4.4
search this.searchdomain.com # The search domain that we got from step 2
EOF
As Administator in Windows Powershell
Change Cisco Anyconnect metric from default 1 to 6000 inside powershell
Get-NetAdapter | Where-Object {$_.InterfaceDescription -Match "Cisco AnyConnect"} | Set-NetIPInterface -InterfaceMetric 6000
Restart wsl2 on the same elevated powershell, then you can open up wsl2 and it should connect to the internet.
Restart-Service LxssManager