This article explains the CRC/Alignment Errors with Half-duplex devices on some ports of the EX2300 models & the limitations to it

• We see CRC errors incrementing on the half-duplex device-connected ports, except for the first 16 ports

root> show interfaces extensive <>

Physical interface: ge-0/0/17, Enabled, Physical link is Up

Interface index: 666, SNMP ifIndex: 532, Generation: 157

Link-level type: Ethernet, MTU: 1514, LAN-PHY mode, Link-mode: Half-duplex, Speed: Auto, BPDU Error: None, Loop Detect PDU Error: None, Ethernet-Switching Error: None, MAC-REWRITE Error: None, Loopback: Disabled, Source filtering: Disabled, Flow control: Disabled, Auto-negotiation: Enabled, Remote fault: Online, Media type: Copper, IEEE 802.3az Energy Efficient Ethernet: Disabled, Auto-MDIX: Enabled

Input errors:

Errors: 34157, Drops: 0, Framing errors: 34157, Runts: 0, Policed discards: 0, L3 incompletes: 0, L2 channel errors: 0, L2 mismatch timeouts: 0, FIFO errors: 0, Resource errors: 0

MAC statistics: Receive Transmit

CRC/Align errors 34157 0

Autonegotiation information:
    Negotiation status: Complete
    Link partner:
        Link mode: Half-duplex, Flow control: None, Remote fault: OK, Link partner Speed: 10 Mbps
    Local resolution:
        Flow control: None, Flow control tx: Disabled, Flow control rx: Disabled, Remote fault: Link OK, Local link Speed: 10 Mbps, Link mode: Half-duplex

It's a hardware limitation on EX2300 models.

On EX2300-24T switches, only the ports labeled 0/0 through 0/15 support half-duplex.

On EX2300-48T switches, only the ports labeled 0/0 through 0/15 and 0/24 through 0/39 support half-duplex.

Reference - https://www.juniper.net/documentation/us/en/hardware/ex2300/topics/topic-map/ex2300-chassis.html#id-rj-45-network-port-leds-and-uplink-port-leds-in-ex2300-switches__d56e221

https://www.juniper.net/documentation/us/en/hardware/ex2300/topics/topic-map/ex2300-chassis.html#id-rj-45-network-port-leds-and-uplink-port-leds-in-ex2300-switches__d56e221