Wireless Joint

I have a NEXP6GO router with a EM12 cellular modem. I have an ASUS 68U router connected to the LAN output of the WiFix router. The ASUS router is used for connecting devices either through ethernet or WiFi. I realize that I have a double NAT, but that is not a problem. I am not exactly clear what the TTL of packets going out via the cellular modem will be, will the NEXP6GO router set the TTL of outgoing packets, or will it decrement the TTL generated by the ASUS by one? The NEXP6GO is setup for a TTL of 64 and the mangle is also set to that. If the ASUS router is set to a TTL of 64, will the outgoing packets via the cellular modem have a TTL of 64 or 63?

The NEX router will set the outgoing packets TTL/HL at the interface in the rule with POSTROUTING. So if you are using wwan0 (modem) then you should be good for all traffic.