Hi,
I’m experiencing persistent connection issues with Battle.net that seem to be directly related to my home network setup — more specifically, to the use of CGNAT by my ISP.
Problem description:
- On my PC (connected via Ethernet to my home router), Battle.net fails to connect and shows error: BLZBNTBNA00000005
- On my mobile device (Steam Deck over the same home Wi-Fi), I get: BLZBNTBNA00000028
- When I connect any of these devices via GSM hotspot (mobile 4G network), Battle.net connects immediately and works fine.
- This issue started recently. Previously, everything worked flawlessly on the same home setup.
What I’ve already tried:
- Full cleanup of Battle.net cache and files (ProgramData, AppData, etc.)
- Reinstalling the app
- Disabling firewall/antivirus entirely
- Testing on multiple devices (PC, laptop, phone)
- Router resets, DNS flushes, changing ports, switching to Google DNS
- Traceroute confirms packets reach Battle.net servers with no blockage or timeout (other than expected hops)
What I discovered:
- My ISP is using CGNAT (Carrier-Grade NAT) and assigning me a non-public IPv4 address in the 100.x.x.x range.
- My external IP is in the 100.112.x.x or 100.113.x.x range — which confirms it’s not publicly routable.
- When I asked my ISP for a public IP, they offered it only as a paid add-on.
- Given that Battle.net used to work fine before this, I suspect Blizzard servers may have recently changed something in how they handle connections from CGNAT IPs.
What I’d like to know:
- Does Battle.net require a public IPv4 address to connect and maintain sessions?
- Is CGNAT a known issue that blocks proper communication with your authentication or update servers?
- Is there any workaround on the Blizzard side, or is a public IP absolutely required for now?
I want to avoid paying extra for a public IP from my ISP unless it’s confirmed to be the only solution — especially since this worked before.
Thanks in advance for any insight or confirmation from Blizzard tech staff or anyone with similar experience!