Passive XS+DA0001 DAC between an RB3011 SFP port and a CRS309 SFP+ port only links after limiting advertised speeds
The poster wanted to use a MikroTik XS+DA0001 passive DAC between the 1G SFP port of an RB3011 and an SFP+ port of a CRS309 and asked whether a passive cable can bridge different SFP generations. The RB3011 SFP cage is 1G only while the CRS309 cage is SFP+ (10G), and a passive DAC has no active electronics to bridge the two rates, so the link stayed down until the advertised speeds were aligned.
- Hardware: MikroTik RB3011, MikroTik CRS309-1G-8S+, MikroTik RB4011
- Transceivers: MikroTik XS+DA0001 DAC, third-party 10G DAC
- Form factor: SFP, SFP+, DAC
Symptoms / messages:
no link between SFP and SFP+ ports over passive DAC
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Comments 2
The poster got it working by removing all speeds above 1G from the advertised list on the CRS309 SFP+ port to match the RB3011's 1G maximum.
Passive DACs expect the same SFP generation on both ends; an active DAC may be required. Another user ran a third-party 10G DAC between a 4011 and a 3011 by forcing 1G.