Configuring TAP Interface

Hi, what I am trying to do is to connect my home router to a router in the work office using 4G SIM cards , the SIMs are up and when I ping from one router to the other using the SIM IP it is working, but if I connect for example my laptop to the router it is not connected to the office network.

Here what I have done :

I created Tap interface using following command:

ip tuntap add tap_hq mode tap. and it shows up when I ran > ifconfig :

tap_hq Link encap:Ethernet HWaddr 5A:1B:4D:CE:3B:85 UP BROADCAST MULTICAST MTU:1500 Metric:1 RX packets:0 errors:0 dropped:0 overruns:0 frame:0 TX packets:0 errors:0 dropped:0 overruns:0 carrier:0 collisions:0 txqueuelen:1000 RX bytes:0 (0.0 B) TX bytes:0 (0.0 B).
but the link status is down , when I ran the command > ip link : tap_hq: <NO-CARRIER,BROADCAST,MULTICAST,UP> mtu 1500 qdisc fq_codel master br-lan state DOWN mode DEFAULT group default qlen 1000 link/ether 5a:1b:4d:ce:3b:85 brd ff:ff:ff:ff:ff:ff

I tried to bring it up using the following command :

ip link set tap_hq up but still it shows status down.
Can any one help me.

'SIM IP' is private one, it is senseless.

Yes it is , but it was configured by the operator to link the 2 routers .

What is OpenVPN config of your server, and client, omitting private information?

Hi , thanks for your question , I don't use OpenVPN .
to be more descriptive , how can I solve the (No carrier ) link problem , I read that I have to create a process with QMEU , so how can I crate this process ?

I doubt that the carrier's "private tunnel" supports layer 2. You would need to encapsulate packets with a protocol like GRE(tap) or VXLAN. Or simply use layer 3 routing, which is generally preferable. Layer 2 tunneling from a large network will send a lot of unnecessary broadcast traffic through the link.

The protocols above do not encrypt or authenticate the connection. Any LAN access that leaves the site should be within a VPN no matter how much you trust the phone company.

As already suggested, examine the configuration of the network you are trying to connect to to see what it is expecting from you.