NFX has VNF (virtualized network function) configured with SR-IOV interfaces. The front panel interface is connected to a switch which is negotiated to full-duplex. However, the VNF interface that is mapped to that physical interface shows as half-duplex.
Topology:
EX Switch === (ge-0/0/0) NFX250 Front Panel ======= ge-0/0/1 vSRX VNF Interface
In this example, ge-0/0/0 is directly connected to an EX switch with auto-negotiated duplex. When looking at the NFX250 front panel ge-0/0/0 interface, it shows full duplex:
{master:0}
jdm-sysuser> show interfaces ge-0/0/0
Physical interface: ge-0/0/0, Enabled, Physical link is Up
Interface index: 647, SNMP ifIndex: 509
Link-level type: Ethernet, MTU: 9216, LAN-PHY mode, Link-mode: Full-duplex,
Speed: Auto, BPDU Error: None, Loop Detect PDU Error: None,
However, when looking at the VNF Interface (which is mapped to front panel interface ge-0/0/0, it shows as half-duplex:
[edit]
root# run show interfaces ge-0/0/1
Physical interface: ge-0/0/1, Enabled, Physical link is Up
Interface index: 136, SNMP ifIndex: 511
Link-level type: Ethernet, MTU: 1514, LAN-PHY mode, Link-mode: Half-duplex,
Intel's DPDK driver version 17.02 had a bug which caused VNF interfaces running that version to come up as half-duplex.
Check your VNF vendor to see what version of the DPDK SR-IOV driver the interface is supporting. If it is using DPDK version 17.02, it will most likely match this bug. The fix for this is included in DPDK version 17.2.
On vSRX, DPDK 17.2 has been included in JUNOS 15.1X49-D150, and 18.2R2 and higher.
On non-vSRX VNF's, please check with the vendor, and ensure it is using DPDK driver version 17.2 or higher.