te vas a la carpeta donde tengas instalado el cs, si por ejemplo lo tienes en "c:\cs" te vas a c:\cs\platform\config ahi abres el masterservers.vdf borras el contenido y pones esto:
"MasterServers"
{
"hl1"
{
"0"
{
"addr" "72.165.61.189:27010"
}
"1"
{
"addr" "68.142.72.250:27010"
}
"2"
{
"addr" "69.28.151.162:27010"
}
}
"hl2"
{
"0"
{
"addr" "69.28.140.246:27011"
}
"1"
{
"addr" "68.142.72.250:27011"
}
"2"
{
"addr" "72.165.61.189:27011"
}
}
"rdkf"
{
"0"
{
"addr" "67.132.200.140:27012"
}
}
}