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The relationship between PFE's and switch ports for the EX-series Ethernet Switches

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Article ID: KB10963 KB Last Updated: 05 Mar 2017Version: 5.0
Summary:
EX-series Ethernet Switches employ a fully-distributed forwarding architecture and they are implemented through PFEs. A PFE is a special ASIC developed by Juniper for EX-series switches. Different models of EX switches have different numbers of PFEs and the number of PFEs determines the total number of available access ports on the EX3200-series. (Access ports are all those switch ports other than the uplink module ports.)
Symptoms:

Solution:
The numbers of PFEs on the different models of EX-series switches are as follows:
  • 24-port EX4200 – 2 PFEs
  • 48-port EX4200 – 3 PFEs
  • 24-port EX3200 – 1 PFE
  • 48-port EX3200 – 2 PFEs

PFEs are in charge of all 1GbE ports, including both 1GbE access ports and 4x1GbE uplink module ports. A PFE can support up to 24x1GbE ports. Thus, for the EX4200-series switches, there are enough PFEs to handle all ports, while EX3200-series switches do not have enough PFEs for all ports.

Examples.
  • 24-port EX4200 – 2 PFEs
    One PFE is used for the 24 access ports and the other is for the 4 uplink ports.

  • 48-port EX4200 – 3 PFEs
    Two PFEs are used for the 48 access ports and the other is for the 4 uplink ports.

  • 24-port EX3200 – 1 PFE
    4 ports cannot be supported since it has a total of 28 ports(24 access ports and 4 uplink ports).

  • 48-port EX3200 – 2 PFEs
    4 ports cannot be supported since it has a total of 52 ports(48 access ports and 4 uplink ports).


Note that, for EX3200-series switches, the 4 unsupported ports are the last 4 access ports. That is, the last 4 access ports are excluded from the whole switch ports. So, you can use all of the uplink ports and only 20 or 44 1GbE access ports.

Here is the 'show interface terse' output with and without the 4x1GbE uplink module.

  • Without 4x1GbE uplink module
    juniper@ex3200-24p> show interfaces terse
    Interface               Admin Link Proto    Local                 Remote
    ge-0/0/0                up    down
    ge-0/0/1                up    down
    ge-0/0/2                up    down
    ge-0/0/3                up    down
    ge-0/0/4                up    down
    ge-0/0/5                up    down
    ge-0/0/6                up    down
    ge-0/0/7                up    down
    ge-0/0/8                up    down
    ge-0/0/9                up    down
    ge-0/0/10               up    down
    ge-0/0/11               up    down
    ge-0/0/12               up    down
    ge-0/0/13               up    down
    ge-0/0/14               up    down
    ge-0/0/15               up    down
    ge-0/0/16               up    down
    ge-0/0/17               up    down
    ge-0/0/18               up    down
    ge-0/0/19               up    down
    ge-0/0/20               up    down         <<<<<<<<<<
    ge-0/0/21               up    down         <<<<<<<<<<  The last 4 access ports
    ge-0/0/22               up    down         <<<<<<<<<<    show up
    ge-0/0/23               up    down         <<<<<<<<<<
    bme0                    up    up 
    --- snip

  • With 4x1GbE uplink module
    juniper@ex3200-24p> show interfaces terse   
    Interface               Admin Link Proto    Local                 Remote
    ge-0/0/0                up    down
    ge-0/0/1                up    down
    ge-0/0/2                up    down
    ge-0/0/3                up    down
    ge-0/0/4                up    down
    ge-0/0/5                up    down
    ge-0/0/6                up    down
    ge-0/0/7                up    down
    ge-0/0/8                up    down
    ge-0/0/9                up    down
    ge-0/0/10               up    down
    ge-0/0/11               up    down
    ge-0/0/12               up    down
    ge-0/0/13               up    down
    ge-0/0/14               up    down
    ge-0/0/15               up    down
    ge-0/0/16               up    down
    ge-0/0/17               up    down
    ge-0/0/18               up    down 
    ge-0/0/19               up    down
    ge-0/1/0                up    down     <<<<<<<<<  The last 4 access ports disappeared
    ge-0/1/1                up    down     <<<<<<<<<   and 4 uplink module ports
    ge-0/1/2                up    down     <<<<<<<<<   show up instead
    ge-0/1/3                up    down     <<<<<<<<<
    bme0                    up    up 
    ---- snip

NOTE: The restriction is only for the EX3200-series and applies only when the 4x1GbE uplink module is in use. If a 2x10GbE uplink module is used instead, then you can still have all 24 or 48x1GbE access ports and 2x10GbE uplink ports.
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