Add this four lines in your server.cfg

sv_forceIndirectListing true
sv_listingHostOverride "PROTECTED PROXY IP:PORT"
sv_listingIpOverride "PROTECTED PROXY IP:PORT"
sv_proxyIPRanges "173.245.48.0/20 103.21.244.0/22 103.22.200.0/22 103.31.4.0/22 141.101.64.0/18 108.162.192.0/18 190.93.240.0/20 188.114.96.0/20 197.234.240.0/22 198.41.128.0/17 162.158.0.0/15 172.64.0.0/13 131.0.72.0/22 104.16.0.0/13 104.24.0.0/14"

Copy and Replace PROTECTED PROXY IP:PORT which includes the numbered IP address and port of our Lectron DDoS protected proxy

Example