Does anyone from Cisco or Mikrotik know how to fix a tcp packet on the fly?

Question

Mikrotik

There is a piece of iron.
Connects to the server via telnet. Communicates by text.
At the beginning of the session, the server asks:
> GetSerialNumber The piece of iron
answers
> MySerial is: 111111.
Everything works well. When a piece of iron "breaks", another one is put in its place. And this one for the fix.
But the trouble is, the second piece of iron answers MySerial is: 111112.
And for the server, it is already another piece of iron.
In order not to reconfigure anything, a crutch was made:
Mikrotik, which distributes the Internet for this good, intercepts the connection from the piece of iron to the server and forwards it to a nearby computer on Windows. Where is the proxy on python.
The proxy looks at the answers of the piece of iron and if it sees the serial 111112 there, it changes it to 111111 and sends it back to the server.
Everything works well.
I would like to remove the weak link - a computer on Windows.
Since the serial numbers are of the same length, the idea came to Mikrotik himself to change the contents of the package "on the fly", correct the CRC and send it to the server. No intermediate proxy server.
Here in connection with this vporos. Can this be done in Mikrotik? And what crutch?
If not, is it possible on cisco 871 or at least on cisco 1811 and how?

Answer 1

Sorry, but I would like to understand the sacred meaning of this action. You may be more comfortable going the other way.
As for the Cisco network equipment (routers and switches), I do not know the functionality of IOS / IOS-XE that would allow me to interfere so deeply with traffic.
Serial equipment can also be received via SNMP. But if you have device identification in the topological hierarchy according to this parameter, then here, it seems to me, you need to bind not to Serial but to Hostname, which is easily sewn by the same SNMP.
In order not to reconfigure anything in a combat environment, you must configure the equipment before installing it in the prod. This is called "commissioning". Otherwise costЫl.sh will accompany you forever.