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(Supplement): FAQ: Explaining the Internet "Cannot operate transceiver"

Modem Broadband Router

Internet

Fig. 1
As shown in Fig. 1, even though only one broadband router (BBR) is visible on the network,
in reality there are two. (Duplex router phenomenon.)
There are multiple modems with built-in BBR functions, so when connecting such a modem
as described above, there must not be two BBR paths connecting the PC to the internet.
Consequently, even if the open port has been set for one BBR only, the required KNS
packets will not flow. For this reason, either set the required KNS port to open for both BBRs,
or stop one BBR function, and set the network so that there is only one BBR on the network.
Internet Modem Broadband Router
Fig. 2
As shown in Fig. 2, the case where a telephone is connected directly to a modem, in most
models the modem has a built-in BBR function. In such cases, stopping the function of the
BBR built into the modem stops the VoIP telephone functions connected to the modem, so
VoIP telephony use is disabled.
To prevent the VoIP telephone functions from stopping, stop the functions of the BBR
connected to the front of the PC, and set the port required by KNS to open in the BBR built
into the modem.