TL;DR Different devices on my LAN are showing different external IP addresses, and none of them are VPN clients.
I recently identified a weird issue where multiple devices attached on the same LAN interface show different external IP addresses. It seems that each unique physical port maps to a different external IP.
I'm not sure if this is some weird issue on my internal network config or an artifact of carrier grade NAT on ATT LTE (My ISP).
Details of my setup:
Using a Netgear LB1120 with ATT SIM Card as my WAN gateway.
Open-WRT (OpenWrt 18.06.2 r7676-cddd7b4c77 / LuCI openwrt-18.06 branch (git-19.020.41695-6f6641d)) configured with the LB1120 on the WAN interface. Configured both wireless and physical interfaces as part of the LAN firewall zone.
It seems like each physical interface is mapped to a different external IP (ie. on wifi I see IP A on icanhazip.com, on an ethernet connected computer I see IP B, on another ethernet connected computer (different port) I see IP C) Each of these devices are on the same internal LAN and can talk to each other with no problems. None of these are configured as vpn clients
Someone on another forum suggested this could be caused by VPN/IP Passthrough. I found that setting enabled on my LB1120 and have disabled it, but it doesn't appear to have resolved the issue.
Has anyone seen anything similar? Scratching my head on this. Please let me know if there are more details I can provide.
config interface 'lan' option type 'bridge' option proto 'static' option netmask '255.255.255.0' option ip6assign '60' option ipaddr '192.168.1.1' option dns '192.168.1.3' option ifname 'lan0 lan1 lan2 lan3' config interface 'wan' option ifname 'eth2' option proto 'static' option ipaddr '192.168.5.2' option netmask '255.255.255.0' option gateway '192.168.5.1' option metric '1'