QFX-QSFP-DAC-xM-BCC | Juniper Compatible QSFP to QSFP Copper DAC Cable, 40GB, 40GBASE-CR4 | 1 to 5M

Q: Will this work in place of the Juniper QFX-QSFP-DAC-1M?
A: Yes. The QFX-QSFP-DAC-xM-BCC is designed to replace the Juniper QFX-QSFP-DAC-1M and related length variants. It shares the same QSFP+ form factor, 40GBASE-CR4 standard compliance, and 40 Gbps data rate, ensuring plug-and-play compatibility. The cable is programmed to meet Juniper platform requirements and operates identically to the OEM part in QFX and EX series switches with QSFP+ ports.

Q: Which Juniper platforms support this cable?
A: This cable is compatible with Juniper switches and routers featuring QSFP+ ports that support 40GBASE-CR4. While specific platform compatibility depends on the port specifications, any Juniper device with standard QSFP+ 40G Ethernet ports adhering to IEEE 802.3ba and QSFP+ MSA SFF-8436 will support this cable. Verify that your target platform lists 40GBASE-CR4 or QSFP+ DAC compatibility in its hardware documentation.

Q: What is the maximum distance for passive copper at 40 Gbps?
A: Passive copper DAC cables like this one are limited to 5 metres maximum reach at 40 Gbps due to signal attenuation and insertion loss in copper twinax. Beyond 5 metres, the signal degrades below the receiver sensitivity threshold required for 40GBASE-CR4 without active signal regeneration. For distances beyond 5 metres, consider active copper (up to 10m) or fibre optic transceivers with appropriate fibre patch cables.

Q: Can I mix cable lengths within the same switch?
A: Yes. Each QSFP+ port operates independently, so you can use different cable lengths (1m, 3m, 5m) across ports within the same switch without issues. The passive design has no inter-port dependencies, and the 40GBASE-CR4 standard defines fixed electrical characteristics regardless of cable length within the 5-metre passive limit. Lane timing and signal integrity are maintained per-port, allowing arbitrary length combinations across your rack topology.

Q: Does this cable support FEC or require host-side FEC configuration?
A: The 40GBASE-CR4 standard (IEEE 802.3ba Clause 85) does not mandate forward error correction for copper DAC links under 5 metres. Most switches auto-negotiate link parameters and do not require manual FEC enablement for passive DAC connections at this distance. However, some platforms may enable FEC by default for all 40G links. Check your switch configuration if link errors occur, though passive copper under 5m typically establishes error-free links without FEC intervention.