Supported Active Physical Rate-Selectable Ports to Prevent Oversubscription on MX204 Router

 

The maximum capacity of an MX204 router is 400 Gbps, which cannot be oversubscribed. In MX204, the network ports are available in two groups (referred to as PICs), with restrictions around the number and type of ports that can be configured without oversubscribtion.

Starting in Junos OS Release 17.4R1, the MX204 supports rate selectability to prevent oversubscription of the Packet Forwarding Engine bandwidth. The MX204 Packet Forwarding Engine has four 100-Gigabit Ethernet QSFP28 ports (referred to as PIC 0 ports) and eight 10-Gigabit Ethernet ports (referred to as PIC 1 ports). Each of the PIC 0 ports can be used as either a 100-Gigabit Ethernet QSFP28 port or a 40-Gigabit Ethernet QSFPP port, or they can be configured as four 10-Gigabit Ethernet ports (using a breakout cable).

If you configure rate selectability at the PIC level, all the ports supporting that port speed are enabled by default. This can lead to oversubscription in certain cases. To prevent the oversubscription, you can configure the number of active ports that operate at the configured speed by using the number-of-ports number-of-active-physical-ports configuration statement. Additionally, interfaces are created only for the active ports.

Note
  • You cannot configure the number of active ports when you configure rate selectability at the port level.

Invalid Port Configuration

You must try to avoid configuring ports that can lead to oversubscription.

Following is an example of an invalid configuration:

If you try to commit an invalid configuration, the configuration gets committed, but the port is not activated. This is because Junos OS allows you to configure a port before a line card is inserted. You will get an error message in the output of the show chassis alarms command and also in the log messages.

Note

When you are in port configuration mode, all the ports are configured as 10-Gigabit Ethernet.

Configuring Active Ports on MX204 Router with Rate Selectability

Table 1 summarizes the active ports with number-of-ports configured but without any rate selectability configuration for an MX204 router. Because there is no rate selectability configured, the default speed is used in these cases.

Table 1: Active Physical Ports on the MX204 Router for Configuring Rate Selectability at PIC level

PIC

Number of Ports (number-of-ports Statement)

Active Ports

PIC Level 10-Gigabit Ethernet Profile

PIC Level 40-Gigabit Ethernet Profile

PIC Level 100-Gigabit Ethernet Profile

PIC 0

0

-

-

-

1

0

-

-

2

0, 1

-

-

3

0, 1, 2

-

-

4

0, 1, 2, 3

-

-

PIC 1

0

-

-

-

1

0

-

-

2

0, 1

-

-

3

0, 1, 2

-

-

4

0, 1, 2, 3

-

-

5

0, 1, 2, 3, 4

-

-

6

0, 1, 2, 3, 4, 5

-

-

7

0, 1, 2, 3, 4, 5 ,6

-

-

8

0, 1, 2, 3, 4, 5, 6, 7

-

-

Table 2 summarizes the active ports without number-of-ports configured but with rate selectability at PIC-level configuration for an MX204 router.

Table 2: Without number-of-ports But with Rate Selectability at PIC Level for MX204 Router

PIC

Active Ports

PIC-Level 10-Gigabit Ethernet

PIC-Level 40-Gigabit Ethernet

PIC-Level 100-Gigabit Ethernet

PIC 0

0-3

0-3

0-3

PIC 1

0-7

-

-

Table 3 summarizes the active ports with number-of-ports configured and rate selectability at PIC-level configuration for an MX204 router.

Table 3: With number-of-ports Rate Selectability at PIC level for MX204 Router

PIC

Number of Ports (number-of-ports Statement)

Active Ports

PIC-Level 10-Gigabit Ethernet

PIC-Level 40-Gigabit Ethernet

PIC-Level 100-Gigabit Ethernet

PIC 0

0

-

-

-

1

0

0

0

2

0, 1

0, 1

0, 1

3

0, 1, 2

0, 1, 2

0, 1, 2

4

0, 1, 2, 3

0, 1, 2, 3

0, 1, 2, 3

PIC 1

0

-

-

-

1

0

-

-

2

0, 1

-

-

3

0, 1, 2

-

-

4

0, 1, 2, 3

-

-

5

0, 1, 2, 3, 4

-

-

6

0, 1, 2, 3, 4, 5

-

-

7

0, 1, 2, 3, 4, 5 ,6

-

-

8

0, 1, 2, 3, 4, 5, 6, 7

-

-