Comment 1 for bug 1846786

Here follows extract of kernel log that shows link to default to 10 Mbps

root@ubuntu1910:~# dmesg | grep -i igb
[ 8.363504] igb: Intel(R) Gigabit Ethernet Network Driver - version 5.6.0-k
[ 8.371363] igb: Copyright (c) 2007-2014 Intel Corporation.
[ 8.371855] igb 0000:01:00.0: PHY reset is blocked due to SOL/IDER session.
[ 8.430438] igb 0000:01:00.0: Intel(R) Gigabit Ethernet Network Connection
[ 8.440508] igb 0000:01:00.0: eth0: (PCIe:2.5Gb/s:Width x4) 00:15:17:b8:18:d8
[ 8.440511] igb 0000:01:00.0: eth0: PBA No: Unknown
[ 8.451863] igb 0000:01:00.0: Using MSI-X interrupts. 4 rx queue(s), 4 tx queue(s)
[ 8.647771] igb 0000:01:00.1: Intel(R) Gigabit Ethernet Network Connection
[ 8.669494] igb 0000:01:00.1: eth1: (PCIe:2.5Gb/s:Width x4) 00:15:17:b8:18:d9
[ 8.669497] igb 0000:01:00.1: eth1: PBA No: Unknown
[ 8.707223] igb 0000:01:00.1: Using MSI-X interrupts. 4 rx queue(s), 4 tx queue(s)
[ 8.718846] igb 0000:01:00.1 enp1s0f1: renamed from eth1
[ 8.927403] igb 0000:01:00.0 enp1s0f0: renamed from eth0
[ 15.063720] igb 0000:01:00.0 mgmt0: renamed from enp1s0f0
[ 15.137690] igb 0000:01:00.0 mgmt0: igb: mgmt0 NIC Link is Up 10 Mbps Full Duplex, Flow Control: None
[ 832.311222] igb 0000:01:00.0: DCA enabled
[ 832.311237] igb 0000:01:00.1: DCA enabled

Then link speed forced through ethtool

[ 1448.089269] igb 0000:01:00.0 mgmt0: igb: mgmt0 NIC Link is Down
[ 1450.509419] igb 0000:01:00.0 mgmt0: igb: mgmt0 NIC Link is Up 1000 Mbps Full Duplex, Flow Control: None
[ 1495.813709] igb 0000:01:00.0 mgmt0: igb: mgmt0 NIC Link is Up 1000 Mbps Full Duplex, Flow Control: RX/TX