can we use Cisco 4900M switch for converting single mode (1G) to multi mode (10G) interface.

Please let me know other possible solutions.

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    Commented Dec 14, 2019 at 18:16

2 Answers 2


Yes, you can (assuming you have the correct optics).

Whenever you have a speed mismatch like this, you can run into queueing problems. If the switch receives traffic from the 10G interface and forwards out the 1G interface, the traffic can be coming in faster than the switch can send it out. The result is the switch will drop frames when its buffers are full. You can enable QoS on the switch so that the most important traffic is given priority.

  • Also, flow-control
    – Ricky
    Commented Jan 9, 2019 at 18:18

None of the modules/linecards that were available for the Cat4900M had GBIC or SFP slots. Quoting from what is left at cisco.com about the Cat4900M

The Catalyst 4900M offers eight fixed wire-speed 10 Gigabit Ethernet ports, and two half-slots which you can fill with any combination of the following:

  • 20-port wire-speed 10/100/1000 (RJ-45) half-card 8-port (2:1) 10
  • Gigabit Ethernet (X2) half-card (Cisco TwinGig Converter Module compatible)
  • 4-port wire-speed 10 Gigabit Ethernet (X2) half-card
  • 8-port (2:1) 10GBASE-T half-card

The only option you have is something like a TwinGig Converter Module that makes two 1Gig SFP ports out of a X2 (unclear if 1G or 10G, here) port (of which the Cat4900M has 8). That will restrict you to optical modules of the SFP form factor. That should not actually a problem, SFP modules are ubiquitous, but require an LC plug on the FO cable.

Be sure that you know the plug's form factor of the 1Gig single mode link before choosing the Cat4900M. If it comes as SC-Duplex, you'll need an additional or different FO patch cord with LC/SC plugs.

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