CRS304-4XG slow link negotiation at 10GbE

I've had a CRS304-4XG for a while now, and about 6 months ago I finally got 10G NICs so that I could utilize it fully. Throughput and link stability (once established) are great, but one thing has been very annoying: retried link negotiations.

After a bunch of tests with various 10G NICs with this switch (and without) I am starting to suspect that something is wrong with the switch itself. I have a CLUB3D CAC-2531 (RTL8159), ASUS XG-C100C V3 (AQC107) and a Zyxel XGN100Cv3 (RTL8127), cat7 and 8 cables are connecting them to the switch. With all of these when I first enable the interface, it can take from only 12 to as much as 25 seconds for a ping -t to start going through.

In the switch's logs I can only see that a port goes up or down, a more telling view of this is Windows's Network Connections panel. I toggle the NICs here for my testing, where after enabling one it goes from Network cable unplugged -> Identifying -> Network cable unplugged -> Identifying -> "Network name".

If I manually set the link to 5GbE, it again becomes consistent and always takes about 8 seconds for the link to become usable, no repeated "Network cable unplugged" states are shown.

When any of these NICs are directly connected to each other with static IPs, skipping the switch, they consistently take 12 seconds to reach a successful ping after enabling the interface, no variability.

Things that don't seem to influence it:

  • Reverting to default config and trying with that
  • Ubuntu vs Windows
  • Moving to another switchport, all of them are the same
  • Cat5e vs cat8 cable
  • Different drivers for the NICs

So I am here now, wondering if anybody else is experiencing this issue with CRS304-4XG, and if I should RMA it or try something else?

Details are missing, such as the configuration and RouterOS version.

Right, here it is:

# 2026-09-03 10:47:29 by RouterOS 7.24.1
# software id = KIZY-7AJS
#
# model = CRS304-4XG
/interface bridge add admin-mac=F4:1E:57:75:19:52 auto-mac=no comment="Default Bridge" name=de
fault_fabric_sw vlan-filtering=yes
/interface ethernet set [ find default-name=ether1 ] l2mtu=9216 mtu=9000 name
=ETH_1_sw
/interface ethernet set [ find default-name=ether2 ] name=ETH_2_sw
/interface ethernet set [ find default-name=ether3 ] name=ETH_3_sw
/interface ethernet set [ find default-name=ether4 ] name=ETH_4_sw
/interface ethernet set [ find default-name=ether5 ] l2mtu=1568 name=ETH
_5_sw
/interface vlan add interface=default_fabric_sw l3-hw-offloading=no name="Guest (VLAN20)" vlan
-id=20
/interface vlan add interface=default_fabric_sw l3-hw-offloading=no name="Isolated (VLAN80)" v
lan-id=80
/interface vlan add comment="Management (VLAN1)" interface=default_fabric_sw name=MGMT1 vlan-i
d=1
/interface bridge port add bridge=default_fabric_sw comment=defconf interface=ETH_1_sw
/interface bridge port add bridge=default_fabric_sw comment=defconf interface=ETH_2_sw
/interface bridge port add bridge=default_fabric_sw comment=defconf interface=ETH_3_sw
/interface bridge port add bridge=default_fabric_sw comment=defconf interface=ETH_4_sw
/interface bridge port add bridge=default_fabric_sw comment=defconf interface=ETH_5_sw trusted
=yes
/interface bridge vlan add bridge=default_fabric_sw comment="Guest (VLAN20) binding" tagged=ET
H_4_sw,default_fabric_sw,ETH_5_sw vlan-ids=20
/interface bridge vlan add bridge=default_fabric_sw comment="Isolated (VLAN80) binding" tagged
=ETH_4_sw,default_fabric_sw,ETH_5_sw vlan-ids=80
/interface bridge vlan add bridge=default_fabric_sw comment="Management (VLAN1) binding" tagge
d=default_fabric_sw vlan-ids=1
/interface ovpn-server server add mac-address=FE:D5:3C:CF:AA:DC name=ovpn-server1
/ip address add address=192.168.15.2/24 comment="SW10 Virtual Interface Address" disabled=
yes interface=default_fabric_sw network=192.168.15.0
/ip address add address=192.168.15.2/24 comment=MGMT1 interface=MGMT1 network=192.168.15.0
/ip dhcp-client
# DHCP client can not run on slave or passthrough interface!
add interface=ETH_5_sw name=client1
/ip dns set servers=192.168.15.1
/ip hotspot profile set [ find default=yes ] html-directory=hotspot
/ip ipsec profile set [ find default=yes ] dpd-interval=2m dpd-maximum-failures=5
/ip route add disabled=no distance=1 dst-address=0.0.0.0/0 gateway=192.168.15.1 routing-table=
main scope=30 suppress-hw-offload=no target-scope=10
/ip service set ftp disabled=yes
/ip service set telnet disabled=yes
/ip service set www disabled=yes
/ip service set winbox available-from=192.168.0.0/16 max-sessions=3
/system clock set time-zone-name=Europe/Budapest
/system identity set name=SW10
/interface bridge port add bridge=default_fabric_sw comment=defconf interface=ETH_2_sw
/interface bridge port add bridge=default_fabric_sw comment=defconf interface=ETH_3_sw
/interface bridge port add bridge=default_fabric_sw comment=defconf interface=ETH_4_sw
/interface bridge port add bridge=default_fabric_sw comment=defconf interface=ETH_5_sw trusted
=yes
/interface bridge vlan add bridge=default_fabric_sw comment="Guest (VLAN20) binding" tagged=ET
H_4_sw,default_fabric_sw,ETH_5_sw vlan-ids=20
/interface bridge vlan add bridge=default_fabric_sw comment="Isolated (VLAN80) binding" tagged
=ETH_4_sw,default_fabric_sw,ETH_5_sw vlan-ids=80
/interface bridge vlan add bridge=default_fabric_sw comment="Management (VLAN1) binding" tagge
d=default_fabric_sw vlan-ids=1
/interface ovpn-server server add mac-address=FE:D5:3C:CF:AA:DC name=ovpn-server1
/ip address add address=192.168.15.2/24 comment="SW10 Virtual Interface Address" disabled=
yes interface=default_fabric_sw network=192.168.15.0
/ip address add address=192.168.15.2/24 comment=MGMT1 interface=MGMT1 network=192.168.15.0
/ip dhcp-client
# DHCP client can not run on slave or passthrough interface!
add interface=ETH_5_sw name=client1
/ip dns set servers=192.168.15.1
/ip hotspot profile set [ find default=yes ] html-directory=hotspot
/ip ipsec profile set [ find default=yes ] dpd-interval=2m dpd-maximum-failures=5
/ip route add disabled=no distance=1 dst-address=0.0.0.0/0 gateway=192.168.15.1 routing-table=
main scope=30 suppress-hw-offload=no target-scope=10
/ip service set ftp disabled=yes
/ip service set telnet disabled=yes
/ip service set www disabled=yes
/ip service set winbox available-from=192.168.0.0/16 max-sessions=3
/system clock set time-zone-name=Europe/Budapest
/system identity set name=SW10

Removed serial no. No need for it.

Apart from using VLAN 1, let's forget it, I don't find any configuration errors