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Matt
Asked: 2019-03-07 02:13:41 +0800 CST

How can I connect an rj45 plug into a qsfp28 port?

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I have a mellanox sn2700 switch with qsfp28 100g ports and meet to connect a router for DHCP and internet that only has rj45 ports.

Is there a way to connect the two via an adapter/cable?

Edit:

I am eyeballing the following two adapters and wonder whether anyone ever got this to work:

https://www.amazon.com/10Gtek-Compatible-SFP-GE-T-Transceiver-1000Base-T/dp/B00U77IJ2M/ref=sr_1_1_sspa?keywords=10gtek+rj45+sfp&qid=1552365069&s=gateway&sr=8-1-spons&psc=1

https://www.amazon.com/Mellanox-Network-Adapter-QSFP-MAM1Q00A-QSA/dp/B00FFVFVS0/ref=sxbs_sxwds-stvp?keywords=mellanox+qsa&pd_rd_i=B00FFVFVS0&pd_rd_r=d548f70a-1419-440d-9ffb-fc5672fec5df&pd_rd_w=XC7Rp&pd_rd_wg=ru8ji&pf_rd_p=5c5ea0d7-2437-4d8a-88a7-ea6f32aeac11&pf_rd_r=0NKSBWGSSCVPKGW1NYQ6&qid=1552365080&s=gateway

router

2 Answers

  1. You'll need an interim device. A QSFP28 port can generally be broken out into four 10G interfaces (there are multiple ways of doing this, you'll need to find one that works with both of the devices).

    You would need to a device that accepts a 10G QSFP+ that can also accept a RJ45 that also runs at the speed of your router. For example, not all QSFP+ ports can run at 100Mbps or lower - some can only do 10G or 1G.

    There are 10G switches that have both QSFP+ and 10GBASE-T support, although you may need to insert a regular 1000BASE-T GBIC. Without knowing more about your router it's hard to say.

    Based on the information in the comments, a small device like a Mikrotik CRS305-1G-4S+IN would suffice:

    enter image description here

    Get a 10G breakout cable for your QSFP28 interface and compatible optics for the Mikrotik, then plug your router into the gigabit ethernet interface (or keep that for a management network and throw a regular 1Gb GBIC into one of the SFP+ ports)

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  2. I actually found a better answer to what @Mark Henderson suggested. I received the QSA adapter and GBIT adapter and both in combination allow for a RJ45 1Gbit connector to be plugged into a QSFP28 port on my Mellanox Switch. Here are the components I got which are confirmed to work with the Mellanox SN2700 and HPE SN2700M switches. Total Cost: Around USD 25 (I bought both adapters new on Taobao.com)

    Components needed:

    • 10Gtek for Cisco GLC-T/SFP-GE-T Gigabit RJ45 Copper SFP Transceiver Module, 1000Base-T
    • Mellanox Network Adapter, SFP+ to QSFP (MAM1Q00A-QSA)
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