Modem FRITZ!Box

AVM FRITZ!Box (Cable)

Overview

The AVM FRITZ!Box is a popular cable modem/gateway in Germany and other European markets. DOCSight supports all FRITZ!Box Cable models via the fritzbox driver.

Property	Value
Driver Key	fritzbox
Auth Method	SID-based session
DOCSIS Version	3.0 + 3.1
Default IP	192.168.178.1
Channels	SC-QAM + OFDM (downstream), ATDMA + OFDMA (upstream)

Setup

1. Set Modem Type to AVM FRITZ!Box in DOCSight settings
2. Enter the FRITZ!Box admin password
3. Default modem IP: 192.168.178.1

The driver uses the FRITZ!Box SID-based session authentication and fetches DOCSIS data via the built-in status APIs.

Known Observations

DOCSIS 3.1 Upstream Power +6 dB Offset

The FRITZ!Box displays DOCSIS 3.1 (OFDMA) upstream Power Level approximately 6 dB lower than the scale used by the VFKD signal-value interpretation.

This is a FRITZ!Box-specific interpretation quirk documented in the Vodafone Kabel community reference values: for DOCSIS 3.1 upstream, FRITZ!Box readings need to be interpreted against a scale shifted down by 6 dB. In practice, a FRITZ!Box value around 38-41 dBmV can correspond to the normal VFKD DOCSIS 3.1 upstream range around 44-47 dBmV.

Why this matters: DOCSight evaluates channels against one shared threshold profile. If the FRITZ!Box value were used unchanged, DOCSight would often mark healthy OFDMA upstream channels as too low, while non-FRITZ!Box modems would need a different threshold profile for the same physical line condition.

DOCSight handling: The fritzbox driver applies a +6.0 dB correction to DOCSIS 3.1 upstream channels before analysis. The built-in VFKD thresholds therefore stay on the real interpretation scale and can also be used by other modem drivers without a global FRITZ!Box-only shift.

What you may see: DOCSight can show an OFDMA upstream power value about 6 dB higher than the FRITZ!Box web interface, and some ISP/CMTS tools may also expose the lower modem-reported or DOCSIS reference value. That does not automatically mean DOCSight parsed the channel incorrectly; it means the values may be shown on different interpretation scales. If an ISP tool documents whether its value is modem-reported transmit power, CMTS receive/ranging power, or DOCSIS 3.1 OFDMA reference power, use that source definition when comparing values.

How to verify: Compare DOCSight's upstream power reading for OFDMA channels with the raw value shown in the FRITZ!Box web interface. With the current FRITZ!Box handling, DOCSight should show approximately 6 dB higher.

MSE vs SNR

The FRITZ!Box reports signal quality as MSE (Modulation Error Ratio) using negative dB values. DOCSight uses the absolute value for comparison with standard SNR/MER thresholds.

Bridge Mode

Called "exposed host" or "IP client" mode on the FRITZ!Box. DOCSight continues to work in this configuration as long as the FRITZ!Box web interface remains reachable.

Status: Supported

Related

• Adding Modem Support
• Reference Values (note the FRITZ!Box +6 dB offset explanation)
• Bridge Mode Compatibility