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Understanding Port Oversubscription on Node Devices

Each Node device in a QFabric system can have a different port oversubscription configuration. For example, you can have a Node device with 3:1 port oversubscription, another with 6:1 oversubscription, and yet another with 1:1 oversubscription.

The port oversubscription ratio on a Node device is based on the total amount of bandwidth from the server-facing connections and the total number of uplink connections to the Interconnect devices.. To determine your oversubscription ratio, multiply the number of server ports by the server-port speed, multiply the number of uplink ports by the uplink-port speed, and divide the total server-facing bandwidth by the total uplink-facing bandwidth. For example, If you use 32 10-Gigabit Ethernet server ports (320 gigabits) and 8 40-Gigabit Ethernet uplink ports (320 gigabits) on a QFX3600 Node device, you can configure 1:1 port oversubscription by connecting the eight uplink ports (labeled Q0 through Q7) from the Node device to the Interconnect devices and splitting the remaining 8 40-Gigabit Ethernet ports into 32 10-Gigabit Ethernet server ports.

Other important factors to consider are:

  • When you connect more than one port on a Node device to an Interconnect device, you reduce the overall number of Node devices supported on the QFabric system.

  • When you have two Interconnect devices and a single connection from each Node device, you can connect anyremaining ports as access ports not server ports.

Table 1 shows the oversubscription ratio for ports on QFX3500 Node devices in default mode based on the number of Interconnect devices and the number of connections from each Node device to each Interconnect device.

Table 1: Oversubscription Ratio on QFX3500 Node Devices

Number of Interconnect Devices

Number of Connections from Each Node Device to Each Interconnect Device

Oversubscription Ratio on Node Device

2

1

6:1

2

2

3:1

4

1

3:1

Table 2 shows the oversubscription ratio for ports on QFX3600 Node devices in default modbased on the number of Interconnect devices and the number of connections from each Node device to each Interconnect device.

Table 2: Oversubscription Ratio on QFX3600 Node Devices

Number of Interconnect Devices

Number of Connections from Each Node Device to Each Interconnect Device

Oversubscription Ratio on Node Device

2

1

6:1

2

2

3:1

2

4

1:1

4

1

3:1

4

2

1:1

Table 3 shows the oversubscription ratio for ports on QFX5100-48S Node devices and QFX5100-48T Node devices based on the number of Interconnect devices and the number of connections from each Node device to each Interconnect device.

Table 3: Oversubscription Ratio on QFX5100-48S and QFX5100-48T Node Devices

Number of Interconnect Devices

Number of Connections from Each Node Device to Each Interconnect Device

Oversubscription Ratio on Node Device

2

2

3.5:1

2

1

8:1

4

1

3.5:1

Unlike other Node Devices, the QFX5100-24Q supports the QFX-EM-4Q expansion module, that impact the oversubscription ratio. Table 4 shows the oversubscription ratio for the base model without expansion modules inserted into the device and with two QFX-EM-4Q modules installed. Other factors that impact the oversubscription ratio include the system mode selected for the device. See Table 5 for details on system mode.

Table 4: Oversubscription Ratio on QFX5100-24Q Node Devices

Number of Interconnect Devices

Number of Connections from Each Node Device to Each Interconnect Device

Oversubscription Ratio on Node Device

Oversubscription Ratio on Node Device with Two QFX-EM-4Q Installed

2

1

8:1

12:1

2

2

4:1

6:1

2

4

2:1

3:1

2

8

N/A

1:1

4

1

4:1

6:1

4

2

2:1

3:1

4

4

N/A

1:1

Table 5 shows the ports the default port configuration and identifies the ports that can be converted on Node devices. Because the QFX5100-24Q has expansion bays that allow you to add additional types of ports, see Table 6 for the supported system modes and default configuration of that Node device.

Table 5: Port Configurations on Node Devices

Model

Total Ports

Fixed FTE Ports

Ports that can be configured FTE or XLE

Ports that can be configured XLE or XE

Default Configuration

QFX3500

  • 48 x 10G

  • 4 x 40G

Q0 through Q3

NA

NA

  • 48 x 10G (xe-0/0/0 through xe-0/0/47)

  • 4 x 40G (fte-0/1/0 through fte-0/1/3)

QFX3600

16 x 40G

Q0 and Q1

Q2 through Q7

Q2 through Q15

  • 12 x 40G xle-0/1/4 through xle-0/1/15)

  • 4 x 40G (fte-0/1/0 through fte-0/1/3)

QFX5100-48S and

QFX5100-48T

  • 48 x 10G

  • 6 x 40G

0and 1

2 through 5

2 through 5

  • 2 x 40G (xle-0/1/4 through xle-0/1/5))

  • 4 x 40G fte-0/1/0 through fte-0/1/3)

  • 48 x 10G (xe-0/0/0 through xe-0/0/47)

Note:

Port 2 and port 3 can be configured together as either as XE or XLE. Port 4 and port 5 can be independently configured as XE or XLE.

The QFX5100-24Q can be configured up to 104 10G ports using different system modes to achieve varying levels of port density. See Table 6 for the default configurations for each system mode.

Table 6: QFX5100-24Q System Mode Default Port Configuration

System Mode

Total Ports

Fixed FTE Ports

Ports that can be configured FTE or XLE

Ports that can be configured XLE or XE

Disabled

Default Configuration

QFX-EM-4Q Expansion Modules

Default

24 x 40G (base configuration)

optional expansion model configuration of two modules:

  • 4 x 4 x 10G (QFX-EM-4Q)

0 through 7

8 through 15

8 through 23

Note:

Of these 16 available ports, only 12 may be channelized.

NA

  • 16 x 40G (xle-0/1/8 through xle-0/1/23

  • 8 x 40G (fte-0/1/0 through fte-0/1/7)

Ports in the expansion modules are xe by default.

The expansion module ports are supported, but cannot be channelized. These ports also cannot be converted to XLE or FTE ports

(Xe-0/2/0 through xe-0/2/15 for 1 expansion module and x-0/3/0 and 0/3/15 for a second expansion module)