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Network - Fixing slow downloads problems inside containers and VMs running on Proxmox VE servers with Broadcom BCM57502 NICs
Find out how to fix slow downloads problems inside containers and virtual machines running on Proxmox VE servers with a Broadcom BCM57502 network interface controller by disabling the generic-receive-offload parameter
2025-01-16

Objective

Some Dedicated Servers equipped with Broadcom BCM57502 NICs may experience really slow (as low as 255 kb/s) download speeds inside VMs or containers running on Proxmox VE (Virtual Environment).

Find out how to fix slow downloads problems inside containers and VMs running on Proxmox VE with a Broadcom BCM57502 network interface controller by disabling the generic-receive-offload parameter.

Requirements

The issue is known to occur on bare metal servers of the ADVANCE ranges running Proxmox VE. Only servers equipped with a Broadcom BCM57502 network interface controller are affected.

Instructions

Step 1 - Identifying your network interface controller

SSH into the server and run the following command which lists all PCI devices of class 200 (Ethernet controllers):

lspci -nnd ::200

If the output shows devices with PCI ID 14e4:1752, your server is affected. Example output:

02:00.0 Ethernet controller [0200]: Broadcom Inc. and subsidiaries BCM57502 NetXtreme-E 10Gb/25Gb/40Gb/50Gb Ethernet [14e4:1752] (rev 12)
02:00.1 Ethernet controller [0200]: Broadcom Inc. and subsidiaries BCM57502 NetXtreme-E 10Gb/25Gb/40Gb/50Gb Ethernet [14e4:1752] (rev 12)

Step 2 - Obtaining the network interface names

List network interfaces with:

ip -brief link show

Example output:

lo               UNKNOWN        00:00:00:00:00:00 <LOOPBACK,UP,LOWER_UP>
enp2s0f0np0      UP             9c:6b:00:12:34:56 <BROADCAST,MULTICAST,UP,LOWER_UP>
enp2s0f1np1      DOWN           9c:6b:00:12:34:57 <BROADCAST,MULTICAST>
vmbr0            UP             9c:6b:00:12:34:56 <BROADCAST,MULTICAST,UP,LOWER_UP>

To find the interfaces that correspond to the Broadcom controllers shown by lspci, you can run:

ethtool -i enp2s0f0np0

Example output:

driver: bnxt_en
version: 6.8.12-5-pve
firmware-version: 229.0.121.0/pkg N/A
expansion-rom-version:
bus-info: 0000:02:00.0
supports-statistics: yes
supports-test: yes
supports-eeprom-access: yes
supports-register-dump: yes
supports-priv-flags: no

The bus-info line matches the PCI address (02:00.0 shown by lspci).

Step 3 - Disabling the generic-receive-offload parameter

You can now check the status of the generic-receive-offload parameter with the following command:

ethtool --show-offload enp2s0f0np0 | grep generic-receive-offload:

Example output:

generic-receive-offload: on

The slow downloads issue can be fixed by disabling generic-receive-offload with the following command:

ethtool --offload enp2s0f0np0 generic-receive-offload off

Example output:

Actual changes:
rx-gro: off
rx-gro-hw: off [not requested]

Step 4 - Persisting the change across reboots

In order to persist the change after the next reboot, the ethtool command may be added to the appropriate interfaces in /etc/network/interfaces as an up command.

For instance:

auto lo
iface lo inet loopback

iface enp2s0f0np0 inet manual
	up ethtool --offload $IFACE generic-receive-offload off

auto vmbr0
iface vmbr0 inet static
	address <IPV4>/32
	gateway 100.64.0.1
	bridge-ports enp2s0f0np0
	bridge-stp off
	bridge-fd 0
	hwaddress 9C:6B:00:12:34:56

iface vmbr0 inet6 static
	address <IPV6>/56
	gateway fe80::1

[!primary] The $IFACE placeholder will be replaced by the interface name on execution. You do not need to replace it with the actual interface name.

Setting the generic-receive-offload parameter on the vmbr0 bridge has no effect, the change must be applied to the physical interfaces.

You can now restart the networking service to apply the configuration:

systemctl restart networking.service

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