How to Fix Firewall Reducing Maximum Download Speed on Celeron J1900 ARH Linux Router

Introduction

This article aims to provide a solution for users who have installed ARH Linux on their Celeron J1900 router and are experiencing reduced maximum download speeds due to the firewall. The connection to the Internet is established via PPPoE. In this guide, we will discuss the key concepts, subtopics, and steps to resolve the issue.

Background

ARH Linux is a popular choice for routers due to its open-source nature and flexibility. However, some users have reported that the firewall installed on the system is causing a reduction in maximum download speeds. This issue is not limited to specific hardware or software versions and can occur on various configurations.

Diagnosis

To diagnose the issue, first, check the current download and upload speeds using the speedtest-cli command. This tool can be installed using the following command:

sudo pacman -S mimi

Once installed, run the command:

speedtest-cli

Take note of the download and upload speeds. If the download speed is significantly lower than the expected value, proceed with the following steps.

Firewall Configuration

The issue might be caused by the firewall blocking certain ports or limiting the bandwidth. To check the current firewall rules, use the following command:

sudo iptables --list

Identify any rules that might be causing the reduction in download speeds. If necessary, modify or remove these rules.

Bandwidth Limit

Another possible cause is the firewall limiting the bandwidth. To check the current bandwidth limit, use the following command:

sudo iptables --list --match mark --mark 0:1

If a limit is found, modify or remove it using the following command:

sudo iptables --table mangle --delete MARK --match mark 0:1 --jump CLASSIFY --log-prefix "Bandwidth limit: " --log-level 6

Netfilter QoS

Another possible solution is to configure Netfilter QoS (Quality of Service) to prioritize the download traffic. Use the following commands to install and configure Netfilter QoS:

sudo pacman -S tc

sudo tc qdisc add dev eth0 root handle 1: htb default 1:

sudo tc class add dev eth0 parent 1: classid 1:1 htb rate  kbps

sudo tc filter add dev eth0 parent 1: protocol ip prio 1 u32 match ip dst 0.0.0.0/0.0.0.0 0xffff flowid 1:1

Conclusion

After following the steps outlined in this article, the maximum download speed should no longer be affected by the firewall. Re-run the speedtest-cli command to verify the improvement. If the issue persists, consider contacting your Internet Service Provider (ISP) for further assistance.