How to count the switch port quantity?

10/25G are pretty simple – a single port is a single port, and total count matches the switch spec. On the contrary, 40/100G ports can be used either
as a single port or turned into four 10/25G ports.

For example, Netberg Aurora 720 switch offers 32x100G ports and could be used as 128 25G ports switch or with other port configuration, such as 104х 25G + 6x 100G.

Of course, the switch mechanical design remains the same. In that case, you need to use so-called break-out or pigtail cables with QSFP/QSFP28 on one side
and four SFP+/SFP28 ports on the other side.

BTW, let’s not forget that 25/100G are backward compatible with 10/40G using the same cables.

How to manage

Physical implementation

The image below demonstrates how Netberg Aurora 220 switch is connected with Netberg Aurora 720 using eight 10G ports on the former and two 100G ports on the latter.

NOS settings.

In this case, you need to perform some adjustments only to Aurora 720 settings. We use ICOS 3.2 for this article.

This is the CLI output before any changes:

(nba720) #show port all

Admin      Physical         Physical     Link          Link        LACP     Actor

Intf        Type    Mode        Mode             Status         Status     Trap        Mode    Timeout

————  ———   —————   ——————   —————     ————    ————    ————  ——–

0/1                     Enable      100G Full                           Down      Enable    Enable   long

0/2                     Enable      100G Full                           Down      Enable    Enable   long

0/3                     Enable      100G Full                           Down      Enable    Enable   long

….

0/32                   Enable     100G Full                           Down      Enable    Enable   long

0/33                   Enable     25G Full                             Detach    Enable    Enable   long

0/34                   Enable     25G Full                             Detach    Enable    Enable   long

0/35                   Enable     25G Full                             Detach    Enable    Enable   long

0/36                   Enable     25G Full                             Detach    Enable    Enable   long

0/37                   Enable     25G Full                             Detach    Enable    Enable   long

…

Ports from 0/1 to 0/32 are 100G ports. Ports from 0/33 to 0/160 are reserved for 25G interfaces; they are disabled so far and not listed to conserve space.

You can change the mode for the one or a group of ports same time:

(nba720) (Config)#interface 0/1

(nba720) (Interface 0/1)#hardware ?
profile         Configures a 40G port as 4x10G or 1x40G. Configures a
100G port as 4x25G or 1x100G

These are all options available:

(nba720) (Interface 0/1)#hardware profile portmode ?

1x100G             Configure the port as a single 100G port
1x40G               Configure the port as a single 40G port
4x10G               Configure the port as four 10G ports
4x25G               Configure the port as four 25G ports

And for the particular port:

(nba720) (Interface 0/1)hardware profile portmode 4x25G

You need to reboot the switch for the changes to take effect and don’t forget to save changes.

Now the CLI output will show different picture:

(nba720) #show port all

Admin      Physical         Physical     Link          Link        LACP     Actor

Intf        Type    Mode        Mode             Status         Status     Trap        Mode    Timeout

————  ———   —————   ——————   —————     ————    ————    ————  ——–

0/1                     Enable      100G Full                           Detach    Enable    Enable   long

0/2                     Enable      100G Full                           Down      Enable    Enable   long

0/3                     Enable      100G Full                           Down      Enable    Enable   long

….

0/32                   Enable     100G Full                           Down      Enable    Enable   long

0/33                   Enable     25G Full                             Down      Enable    Enable   long

0/34                   Enable     25G Full                             Down      Enable    Enable   long

0/35                   Enable     25G Full                             Down      Enable    Enable   long

0/36                   Enable     25G Full                             Down      Enable    Enable   long

0/37                   Enable     25G Full                             Detach    Enable    Enable   long

…

Interface 0/1 down, 25G interfaces in the range from 0/33 to 0/36 are up.

If you want to use 25G port in a 10G mode, you have to declare the speed using the CLI “speed” command:

(nba720) (Interface 0/33)#speed ?

100G             Set speed to ‘100G’.
10G               Set speed to ’10G’.
25G               Set speed to ’25G’.
40G               Set speed to ’40G’.
auto              Enables/Disables automatic negotiation on a port.

(nba720) (Interface 0/33)#speed 10G

Important note

As we all know, 25/100G technology can downgrade to 10/40G speed.

In Broadcom Tomahawk chipset, ports are organized as groups of four signal pairs into one SerDes block. All four ports in the group must have the same speed. If you change speed for one of four ports, other ports will be a malfunction.

In a physical 100G port you need to maintain the same speed for the each fan-out port, i.e. they all have to be 25G or 10G.

For the 25G gear, such as Aurora 620, there are the same rules about the port speed.

Ports 1-4 are grouped in one FalconCore SerDes; ports 5-8 are in another FalconCore SerDes and so on. You have to change them all at one time to avoid malfunction:

For example, Port 5, 6 are all 10Gb and have the link already up. Now change the port 6 to be 25Gb, after that, the port 5’s link will go down very soon.

This is a technology-related caveat and cannot be avoided on the path to 100G.