[QFX] Understanding sxe-0/0/x interfaces on QFX10k platform

Summary:

This article explains the existence of sxe-0/0/x interfaces on QFX10k series devices and why these interfaces are seen on QFX10002 but not in the QFX10008 platform.

Symptoms:

When we check the interfaces in the QFX10002 platform, we may find some sxe-0/0/x interfaces, which are shown to be up.

root@QFX10002> show chassis hardware 
Hardware inventory:
Item             Version  Part number  Serial number     Description
Chassis                                EB272             QFX10002-36Q
Pseudo CB 0     
Routing Engine 0          BUILTIN      BUILTIN           RE-QFX10002-36Q
FPC 0            REV 06   750-092102   BCBC3380          QFX10002-36Q
<snip>

root@QFX10002> show interfaces terse | match sxe 
sxe-0/0/0               up    up
sxe-0/0/1               up    up
sxe-0/0/2               up    up

These interfaces are not found in the QFX10008 platform.

root@QFX10008> show chassis hardware 
Hardware inventory:
Item             Version  Part number  Serial number     Description
Chassis                                EC706             QFX10008
Midplane         REV 10   750-095179   BCAS2807          QFX10008 Midplane
Routing Engine 0          BUILTIN      BUILTIN           RE-QFX10008
Routing Engine 1          BUILTIN      BUILTIN           RE-QFX10008
<snip>

root@QFX10008> show interfaces terse | match sxe

Cause:

The sxe-0/0/x interfaces are the 10G interfaces, which connect to the BRCM CPE (internal) switch, which in turn connects to the CPU.

Originally the PE chip supports both 10GE and PCIe interfaces for local CPU connection.

But even though QFX10k and PTX share the same PE chips, they use the control plane differently.

PTX uses both PCIe and 10GE interface for its control plane traffic.
QFX10k uses only PCIe interface currently.

In QFX10002 platform, sxe-0/0/x is 10GE interface for local CPU connection of each PE chip.

QFX10002-36 has 3 PE chips and it has sxe-0/0/0 ~ 0/0/2.
QFX10002-72 has 6 PE chips and it has sxe-0/0/0 ~ 0/0/5.

Solution:

On QFX10K platforms, these interfaces are no longer used. Even if they exist, they are not functional. So when one such interface is seen on the device, you may safely ignore the presence of them as it is not usable.

Knowledge Base