Very few servers showing up in browser

Title says it all really. Only about eight servers show up in the server browser. It’s not a problem with Steam, as its server browser shows 4,336 Gmod servers. Help?

I remember this happening to me when i had the shittest internet ever. You dont, do you?

I have perfectly good internet and have played plenty of online multiplayer games without problems. Besides, if that was the case, wouldn’t most Garry’s Mod servers not show in the Steam browser as well?

Is your router blocking GMods ports?