Can a 10GbE Switch SFP+ Port be Connected to a Gigabit Switch SFP Port?

NADDOD Neo Switch Specialist Jan 13, 2023

As the network tends to develop at high speed, 10GbE switches are becoming more and more popular in enterprise networks. However, the compatibility issue between SFP and SFP+ has been confusing for many users, such as, can SFP+ ports support SFP optical modules and can SFP ports support SFP+ optical modules? Can the SFP port of a Gigabit switch be connected to the SFP+ port of a 10 Gigabit switch?


What is an SFP Port on a Gigabit Switch?

With the changing transmission rate of Ethernet switch, its port type is also changing, such as SFP port, SFP+ port, SFP28 port, QSFP+ port, QSFP28 port, etc. Among them, SFP port is a compact and hot-swappable network interface with a transmission rate of 1Gbit/s for Ethernet and 4Gbit/s for Fibre Channel system. When SFP optical module is inserted into the SFP port of Gigabit switch with fiber optic patch cable or copper cable, it can realize different distance transmission. For example, the maximum transmission distance is 160 km when using SFP1G-ZXC-55 optical module and LC duplex fiber patch cable, and 100 m when using SFP-GB-GE-T optical module (i.e., electrical port module) and Category 5 network cable.

What is SFP+ Port on 10 Gigabit Switch?

10 Gigabit switches are divided into 10 Gigabit fiber switches and 10 Gigabit copper switches depending on the port type, where 10 Gigabit fiber switches are a type of 10 Gigabit switch with SFP+ ports. SFP+ ports have the same appearance and size as the SFP ports mentioned above, and the biggest difference between the two is that SFP+ ports can support transmission rates up to 10 Gbps. Generally, 10 Gigabit switches come with higher speed uplink ports such as QSFP+ ports, QSFP28 ports to facilitate other higher speed switch connections in the topology.

In Most Cases, SFP Optical Modules Can Be Used on SFP+ Ports

Can a 1G SFP optical module be inserted and used on a 10G SFP+ port? Yes, in most cases, but if you insert an SFP optical module on an SFP+ port, the transmission rate of the link will be reduced to 1Gb and some switches will lock the port at 1G until you reset the switch or run a configuration command. In addition, SFP+ ports typically cannot support rates below 1Gb. This means that SFP+ ports cannot use 100BASE SFP optical modules. In fact, much depends on the switch itself for this issue, as some switches can support it, but some cannot. Currently, many vendors offer 10GbE switches that can insert 10G SFP+ optical modules and 1G SFP optical modules (but not both at the same time) on SFP+ ports, and some vendors offer 10GbE switches that can only support 10G SFP+ optical modules, so if you want to insert SFP optical modules into the SFP+ ports of 10GbE switches, before using them, it is best to Therefore, if you want to plug the SFP optical module into the SFP+ port of the 10GbE switch, it is better to consult the vendor to ensure that the SFP+ port of the 10GbE switch can support dual rate.

Under No Circumstances Can SFP+ Optical Modules Be Used on SFP Ports

Is it possible to use 10G SFP+ optical modules on 1G SFP ports? The answer is definitely “No”. As you know, the rate of the optical module installed on the switch determines the rate of the port link. The SFP+ ports on most 10Gb/s switches today are backward compatible and support 1G SFP optical modules. However, SFP ports on Gigabit switches are not forward compatible, meaning they cannot support 10G SFP+ optical modules.

Can the SFP Port of a Gigabit Switch Be Connected to the SFP+ Port of a 10 Gigabit Switch?

As can be seen above, usually SFP optical modules and SFP+ optical modules can be supported on SFP+ ports, while SFP optical modules can only be supported on SFP ports not SFP+ optical modules, so the connection between the two ends is mainly divided into the following two cases.

● When an SFP+ optical module is used on the SFP+ port of a 10 Gigabit switch and an SFP optical module is used on the SFP port of a Gigabit switch, the SFP+ port of the 10 Gigabit switch cannot be connected to the SFP port of the Gigabit switch. Because the SFP+ optical module does not support auto-negotiation technology (auto-negotiation is based on electrical pulses instead of optical pulses, it can only be realized on twisted pair, not on fiber), it cannot adjust the rate to 1G, and this connection method is invalid.

● When SFP optical module is used on the SFP+ port of 10 Gigabit switch and SFP optical module is used on the SFP port of Gigabit switch, the SFP+ port of 10 Gigabit switch can be connected to the SFP port of Gigabit switch, and the link can work normally at this time, and its link transmission rate is 1G.


In summary, most SFP+ ports can support SFP optical modules, but SFP ports cannot support SFP+ optical modules. When inserting 1G SFP optical modules into SFP+ ports on 10G switches, the 10G SFP+ port rate will be reduced to 1G, which means that SFP+ ports on 10G switches can be connected to SFP ports on Gigabit switches, but the transmission rate of the link is 1G at this time. so, to ensure the normal operation of the network, the optical modules used at both ends must be compatible with each other.