Why Does My Device Receive a 192.0.0.x , 192.168.225.x, 10.172.72.x , or Other Private IPv4 Address?

Issue

You observe the network interface connected to the IG is assigned an IPv4 address of 192.0.0.x (RFC 6333) or another address in a private IP range such as 192.168.225.x, 10.172.72.x, etc. (RFC1918).

Cause

IP address assignment is handled differently depending on the specific carrier service plan activated on your SIM card, which Carrier Profile (APN) IP type is being used (IPv4, IPv6, or IPv4v6), which network technology is being used to connect (ex. LTE vs. 5G), and if IP Passthrough (IPPT) is enabled on the IG (enabled by default).

The Ethernet connection on the IG is a bridge interface which by default passes the IP address assigned by the carrier network through to the connected device by default which eliminates a layer of NAT. This is referred to as IP Passthrough (IPPT). When IPPT is enabled and the modem is performing IPv6 translation, you may receive a 192.0.0.x (RFC6333) address on the IG connected device.

By default, the IPPT address is automatically assigned to the MAC address of the IG connected device. Alternatively, the MAC address used for the IPPT bridge can be specified manually in the IG ‘Local IP and Multiple Device’ menu option for advanced setups. IPPT can be disabled entirely in which case the connected device will be assigned an IPv4 NAT address in the same subnet as the Local IP assigned to the IG unit (by default ‘192.168.225.1’). You may also see this NAT address instead of an IPPT address if there was some delay or issue in carrier DHCP address assignment when connecting to the cellular network.

Due to a large mix of both IPv4 and IPv6 addresses in use across the Internet, translation is needed between the two. IPv6-to-IPv4 translation is referred to by several terms including ‘CLAT’, ‘XLAT’, ‘Dualstack-Lite’, ‘DS-Lite’, etc. depending on which side of the connection is being referred to in context (carrier side vs. client side). For widest compatibility across devices, most IG Carrier Profiles use an IP type of IPv4v6 to ensure the modem is performing the needed translation (CLAT).

On some carrier LTE and 5G Non-Standalone (NSA) connections, a legacy IPv4 address in a public range may be provided via IPPT (instead of 192.0.0.x). Such an IP is usually a Carrier Grade NAT (CGNAT) address which is not publicly routable (ex. 26.x.x.x). Conversely, 5G Standalone (SA) connections on some carriers provide IPv6 exclusively so IPPT will only provide an IPv4 of 192.0.0.x used for translation. Some carrier plans will not connect to the network at all if an IP type of IPv4 only is used in the Carrier Profile. Other carriers may assign private CGNAT IP addresses such as 10.172.72.x. and may not yet fully support IPv6 client address assignment depending on the plan and Carrier Profile used.

If you require a publicly routable IPv4 address from your carrier (one which is not behind CGNAT and/or firewalled) in most cases, you will need to sign up for a business account with a service plan that provides static IPv4 addresses. Carriers may choose to offer static IPv6 addresses at some point, but this does not seem to be the case currently (at least in the USA).