Short Reach Mode on QFX5100-48T

In this post I will discuss about short reach mode feature that is present on QFX5100-48T platform.

QFX5100-48T-6Q platform has 48 10BASE-T ports and 6 QSFP+ ports.

The short reach mode feature allows to save up to 5W of power usage in case it is activated on the 10BASE-T ports that use cables that are less than 10m.

In order to use this feature, you will need to run at least 14.1X53-D30 release and it can be used on ports or port-ranges.

If the feature is activated on ports where the cables are more than 10m, it doesn’t provide any benefit.

Unfortunately there is no CLI command that can be used in order to confirm that the feature is working and that the system is using less power.

To have such information, you will need to use an external power meter to measure accurately the power that is saved.

However, there are some logs generated in various places that can be used to confirm that the feature was activated and we will see this later.

Let’s see this in action. I have a QFX5100-48T:

 

{master:0}[edit]
root@QFX5100-48T# run show version
fpc0:
--------------------------------------------------------------------------
Hostname: QFX5100-48T
Model: qfx5100-48t-6q
Junos: 14.1X53-D40.8
JUNOS Base OS boot [14.1X53-D40.8]
JUNOS Base OS Software Suite [14.1X53-D40.8]
JUNOS Online Documentation [14.1X53-D40.8]
JUNOS Crypto Software Suite [14.1X53-D40.8]
JUNOS Kernel Software Suite [14.1X53-D40.8]
JUNOS Packet Forwarding Engine Support (qfx-ex-x86-32) [14.1X53-D40.8]
JUNOS Routing Software Suite [14.1X53-D40.8]
JUNOS SDN Software Suite [14.1X53-D40.8]
JUNOS Enterprise Software Suite [14.1X53-D40.8]
JUNOS Web Management Platform Package [14.1X53-D40.8]
JUNOS py-base-i386 [14.1X53-D40.8]
JUNOS Host Software [14.1X53-D40.8]

{master:0}[edit]
root@QFX5100-48T#

 

I will activate the feature only on the interfaces that are up:

 

{master:0}[edit]
root@QFX5100-48T# run show interfaces terse | match "up    up" | match xe-
xe-0/0/20               up    up
xe-0/0/20.0             up    up   aenet    --> ae0.0
xe-0/0/21               up    up
xe-0/0/21.0             up    up   aenet    --> ae0.0
xe-0/0/22               up    up
xe-0/0/22.0             up    up   aenet    --> ae0.0
xe-0/0/23               up    up
xe-0/0/23.0             up    up   aenet    --> ae0.0
xe-0/0/24               up    up
xe-0/0/24.16386         up    up
xe-0/0/25               up    up
xe-0/0/25.16386         up    up
xe-0/0/26               up    up
xe-0/0/26.16386         up    up
xe-0/0/27               up    up
xe-0/0/27.16386         up    up

{master:0}[edit]
root@QFX5100-48T#

 

This is how it is activated for the range of ports from 20 to 27:

 

{master:0}[edit]
root@QFX5100-48T# show chassis
aggregated-devices {
    ethernet {
        device-count 2;
    }
}
fpc 0 {
    pic 0 {
        port-range 20 27 {
            short-reach-mode enable;
        }
    }
}

{master:0}[edit]
root@QFX5100-48T#

 

In this moment, you know that you configured the feature, but you don’t know if it’s working or not and how much power it saves. As I mentioned, to know how much power it saves, you need an external power meter so we will not discuss this here.

However, we can tell if the feature is working by looking in these two places.

In the syslog of the FPC where we should see UPDN messages for the ports/port-ranges:

 

{master:0}[edit]
root@QFX5100-48T# run request pfe execute target fpc0 command "show syslog messages"
SENT: Ukern command: show syslog messages
GOT:

--- cut here ---
GOT: [Sun Jan 15 09:26:02 2017 LOG: Debug] UPDN msg to kernel for ifd:xe-0/0/20, flag:2, speed: 0, duplex:0
GOT: [Sun Jan 15 09:26:02 2017 LOG: Debug] UPDN msg to kernel for ifd:xe-0/0/21, flag:2, speed: 0, duplex:0
GOT: [Sun Jan 15 09:26:02 2017 LOG: Debug] UPDN msg to kernel for ifd:xe-0/0/22, flag:2, speed: 0, duplex:0
GOT: [Sun Jan 15 09:26:02 2017 LOG: Debug] UPDN msg to kernel for ifd:xe-0/0/23, flag:2, speed: 0, duplex:0
GOT: [Sun Jan 15 09:26:02 2017 LOG: Debug] UPDN msg to kernel for ifd:xe-0/0/24, flag:2, speed: 0, duplex:0
GOT: [Sun Jan 15 09:26:02 2017 LOG: Debug] UPDN msg to kernel for ifd:xe-0/0/25, flag:2, speed: 0, duplex:0
GOT: [Sun Jan 15 09:26:02 2017 LOG: Debug] UPDN msg to kernel for ifd:xe-0/0/26, flag:2, speed: 0, duplex:0
GOT: [Sun Jan 15 09:26:02 2017 LOG: Debug] UPDN msg to kernel for ifd:xe-0/0/27, flag:2, speed: 0, duplex:0
--- cut here ---

LOCAL: End of file

{master:0}[edit]
root@QFX5100-48T#

 

And in /var/log/chassisd where you should see something like this:

 

{master:0}[edit]
root@QFX5100-48T# run show log chassisd | match short
Jan 15 10:26:02  ch_sfxpc_short_reach_mode_action : Sending Short reach mode message hru IPC for port_low 20 port_high 27 for mode 1

{master:0}[edit]
root@QFX5100-48T#

 

Let’s check now a platform that doesn’t support this feature, QFX5100-48S-6Q:

 

{master:0}[edit]
root@QFX5100-48S# show chassis
aggregated-devices {
    ethernet {
        device-count 1;
    }
}
fpc 0 {
    pic 0 {
        port 6 {
            short-reach-mode enable;
        }
    }
}

{master:0}[edit]
root@QFX5100-48S#

 

After you commit the above configuration, you don’t have any UPDN message in the FPC syslog and you should see the following log in /var/log/chassisd:

 

{master:0}[edit]
root@QFX5100-48S# run show log chassisd | match short
Jan 15 10:31:07  Warning: cfg_ddl_port_short_reach_mode : Short reach mode config is not supported on the platform with i2c id bcd on fpc 0

{master:0}[edit]
root@QFX5100-48S#

 

As I mentioned, the short reach feature is available only on 10BASE-T ports from QFX5100-48T. Let’s see what happens when you try to commit this configuration:

 

{master:0}[edit]
root@QFX5100-48T# show chassis
aggregated-devices {
    ethernet {
        device-count 2;
    }
}
fpc 0 {
    pic 0 {
        port 48 {
            short-reach-mode enable;
        }
    }
}

{master:0}[edit]
root@QFX5100-48T#

 

You get this:

 

{master:0}[edit]
root@QFX5100-48T# commit
[edit chassis fpc 0 pic 0 port 48 short-reach-mode]
  'short-reach-mode enable'
    et-interface does not support this feature
error: configuration check-out failed

{master:0}[edit]
root@QFX5100-48T#

 

Finally, you have the option to disable the feature for some ports where you know it doesn’t bring any benefit having the feature activated.

For instance, coming back to the initial example where the feature was activated on the port range, you decide that you want one port to be excluded. You can use this:

 

{master:0}[edit]
root@QFX5100-48T# show chassis
aggregated-devices {
    ethernet {
        device-count 2;
    }
}
fpc 0 {
    pic 0 {
        port 25 {
            short-reach-mode disable;
        }
        port-range 20 27 {
            short-reach-mode enable;
        }
    }
}

{master:0}[edit]
root@QFX5100-48T#

 

And this would be all about short reach mode feature.

I hope you found this information useful as it’s a good way to save some power.

 

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Paris ARAU

Paris ARAU is a networking professional with strong background on routing and switching technologies. He is a holder of CCIE R&S and dual JNCIE(SP and ENT). The day to day work allows him to dive deeply in networking technologies. Part of the continuously training, he is focusing on Software Defined Network and cloud computing.

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