Q: Will this work in place of the Arista CAB-Q-Q-100G-1M?
A: Yes. This cable is designed as a direct replacement for the Arista CAB-Q-Q-100G-1M and fully complies with IEEE 802.3bj 100GBASE-CR4 electrical specifications. It uses the same QSFP28 form factor, delivers the same 4 x 25Gb/s lane architecture, and provides plug-and-play compatibility with Arista switches supporting 100GbE QSFP28 ports.

Q: Which Arista platforms support this cable?
A: This cable is compatible with any Arista platform featuring QSFP28 ports that support 100GBASE-CR4. This includes data center switches with native 100G interfaces. Check that your specific Arista model supports QSFP28 100GbE connectivity and 100GBASE-CR4 electrical signaling.

Q: What is the maximum distance supported and why is it limited to 5 meters?
A: Passive copper twinax DAC cables support up to 5 meters for 100GBASE-CR4 per IEEE 802.3bj. Beyond 5m, copper insertion loss and crosstalk at 25Gb/s per lane degrade signal integrity below the required Channel Operating Margin. For distances beyond 5m, active copper cables with signal regeneration or optical transceivers are required.

Q: Does this cable require Forward Error Correction to operate?
A: 100GBASE-CR4 typically uses Reed-Solomon FEC (RS-FEC) defined in IEEE 802.3 Clause 91 to compensate for channel impairments and meet the target bit error rate. Most modern switches automatically negotiate and enable RS-FEC on 100G ports. The cable itself is passive and does not implement FEC, but the host interfaces at each end do.

Q: Can I use different cable lengths on the same switch without performance issues?
A: Yes. Each passive DAC cable operates independently on its own physical link. Mixing 1m, 3m, and 5m cables on the same switch will not cause crosstalk or timing issues between ports. The switch PHY adapts equalization and FEC per lane based on the channel characteristics presented by each individual cable.