Question

Hi experts,

today I noticed and verified an effect with my Telktronics RUTX11 which I have never seen before:

Some mobile network operators assign different speeds depending on what type of device is connecting their 4G network. If it is a regular 4G smartphone or a 4G tablet where the SIM card is inserted, I get the full speed possible at my location (150MBit/s DL/50MBit/s UL). 

However, if I use the same SIM card and insert it into the RUTX11 at the same location, same APN settings, same LTE band B3, same signal level, I measure only exact 5MBit/s DL and also 5MBit/s UL . 

My mobile operator is obviously throtteling the 4G speed down as soon as router device like the RUTX11 instead of a common smartphone is connected! I assume they are using the MAC address of the modem to detect that the vendor is not a smartphone manufacturer or the OS is neither Android nor IOS, or they using other info to identify that a router is connected.

Has anyone an idea how I can configure the RUTX11 to pretend and connect to the 4G network like being a regular smartphone?

Thanks for any advise!

Answer 1

Hello,

Thank you for reaching out!

While carriers obviously do not disclose how they detect if mobile data is used by more than one user, usually it is done by inspecting the TTL (Time-to-Live) value of the outgoing packets. If the TTL value is less than 64, then the carrier assumes, that there must be other devices using the same gateway device.

TTL packets get their value decreased every hop, which in practice usually means every router. So if you have a device behind the router, the device sends out a packet with a TTL value of 65, then the router decreases it by 1, and the TTL value is now 64.

To avoid this, the IPtables rule can be used. Navigate to Network → Firewall → Custom Rules and paste this rule:

iptables -t mangle -I POSTROUTING -o wwan0 -j TTL --ttl-set 65

This command is adapted to the RUTX series of devices, running v07.02.7 of RutOS. wwan0 is the mobile interface name and may be different for other devices.

A different command could also be used for increasing the outgoing TTL value:

iptables -t mangle -I POSTROUTING -o wwan0 -j TTL --ttl-inc 1

This will increase the value by 1, but the number can be modified.

The original solution for this was provided here.

More information about TTL target in IPtables can be found here.

This solution does not guarantee, that carrier restriction will be avoided, but it's worth trying out.

Also, you might not be able to achieve the same speed as your mobile device, as the architecture of these devices varies greatly. Please refer to this article for more details.

Let me know if it helped!

Best regards,
DaumantasG

Comments

Hello,

thanks for the quick help. Unfortunately both firewall commands did not change anything after pasting each of them alone into the custom firewall edit window and after mobile interface interface reset of my RUTX11

I am not sure if the TTL issue is the right trace because if I use a regular smartphone with this sim card, put it outside on my balcony and open a mobile wifi hotspot on it, all devices using this smartphone mobile hotspot get full speed both directions.

I assume that my mobile network operator (Vodafone Italia) uses vendor class / ID/ vendor MAC address code detection or similar to decide which speed you get.

Is there a way to spoof the RUTX11 modem MAC address to change the first HEX numbers to e.g pretend being Samsung as device manufacturer? Or maybe send a smartphone vendor class /ID pretending e.g. to be a Samsung Smartphone model S10 to the carrier during the DHCP connection via the 4G modem interface like on the WAN interface?

---

Hello,

Unfortunately, the Mobile interface does not have a MAC address but rather uses IMEI for identification. IMEI could also be used for determining the modem manufacturer and it cannot be changed.
The best course of action would most likely be to contact the operator and inquire about home internet plans.

Best regards,
DaumantasG

---

Hello,

thanks again for your reply, your are right - the modem IMEI also unveils what type of device is connecting. The home internet plans are much more expensive as these 'smartphone usage only' restricted plans.

So I will either deactivate the RUTX11 built in modems and connect an old smartphone as modem at the USB port or I will replace the RUTX11 completely by a regular cheap 4G capable smartphone as mobile hotspot or change the operator.

Thanks anyway for your support. I hope this post will advise other users that some operators start implementing smart measures to exclude SIM router usage for certain internet plans.

---

Hello,

Unfortunately, that could be the only option. However, the carrier may also use two or more APNs (T-Mobile does this in the USA), and when tethering is enabled on the mobile phone, it uses the tethering APN by default, so make sure to delete it.

Let me know if there are any further questions!

Best regards,
DaumantasG

---

Hello

Would we replace wwan0 with mob1s1a1 on the RUTX50?

---

Hello,

RUTX50's physical mobile interface name is qmimux0, so this is the name that should be used in the IPtables commands.

Best regards,
DaumantasG

---

Hi, I have the very same problem on a TRB500. What is the interface name i should use? Same as on the RUTX50?