Hi,
I believe there may be a routing or traffic-filtering issue within the Three Ireland network affecting connections from Three mobile customers to public IPv4 addresses assigned to Three 5G Broadband customers.
Our setup is as follows:
- Source connection: Three Ireland mobile SIM using the default
internet APN
- Broadband connection: Three Ireland 5G Broadband using the
open.internet.public APN
- The broadband connection has a publicly reachable IPv4 address
- Web services are available through the broadband public IP on TCP ports 80 and 443
When the mobile device is connected directly to the Three mobile network, it cannot:
- Ping the broadband public IPv4 address
- Connect to
PUBLIC_IP:80
- Connect to
PUBLIC_IP:443
- Access any web services hosted behind the Three 5G Broadband connection
However, if I use the same mobile device through a Vodafone or Eir connection, the same broadband public IP and web services are immediately reachable without any issues.
The firewall and server configuration do not appear to be the cause, as the public IP and services are accessible from other Irish mobile and broadband networks. The problem appears to affect only traffic originating from the Three mobile network and going to a public IP assigned to a Three 5G Broadband connection using the open.internet.public APN.
The test results can be summarised as follows:
Three Mobile (internet APN) -> Three 5G Broadband public IP:80/443
Result: Connection fails
Vodafone/Eir/Virginmedia -> Three 5G Broadband public IP:80/443
Result: Connection works
Could the Three network team please investigate whether there is an internal routing, NAT, firewall or traffic-filtering issue affecting this Three-to-Three traffic?
The issue is consistent and fully reproducible.
