← Back to articles

ShellCrash on an ASUS RT-AX88U, all devices at home cross the wall

If you own a premium router like the ASUS RT-AX88U, you bought it for its raw processing power: a Broadcom quad-core ARM processor designed to handle massive throughput. Naturally, when you wanted to route your home network around regional firewalls, you probably chose ShellCrash—it installs directly via SSH, avoids the clutter of a secondary “soft-router” box, and keeps your network topology beautifully simple.

But if you are reading this, you’ve likely hit the wall.

Your connection drops out every few days. The router’s admin page becomes unresponsive. Or maybe your domestic traffic slows to a crawl until you manually restart the proxy service.

Let’s look at why this happens on stock ASUS firmware, and the exact adjustments you need to make inside the ShellCrash SSH menu to turn it into a rock-solid gateway.

The Root Problem: Why Premium Hardware Stutters

The RT-AX88U is a routing beast, but its stock ASUS operating system is built on an older, highly customized Linux kernel.

When you run ShellCrash out of the box, it typically defaults to an old Clash core utilizing legacy iptables REDIRECT (Layer 4 redirection). This creates a fatal architectural mismatch:

  1. Socket Deadlocks: Old redirection mechanics break the TCP/UDP socket lifecycle under high concurrency (like downloading torrents or multi-device streaming), causing the router’s network stack to lock up.
  2. Memory Aggression: The Go runtime garbage collection (GC) in old proxy cores doesn’t play nice with the strict memory limits imposed by ASUS firmware. The RAM fills up, the OS kernel invokes the OOM (Out of Memory) killer, and your proxy daemon panics.

Step-by-Step Configuration: Upgrading to a Production-Grade Setup

To fix this, we need to log back into the router via SSH and fundamentally change how ShellCrash interacts with the Linux kernel.

Step 1: Ditch Legacy Clash for the Mihomo Core

The original Clash core is long abandoned. We need to swap it for Mihomo (formerly Clash-Meta), which handles resource allocation infinitely better.

  1. SSH into your router and open the ShellCrash menu by typing crash.
  2. Navigate to 2 核心管理 (Core Management) -> 1 切换核心 (Switch Core).
  3. Select Mihomo (or Meta).
  4. Allow the script to download the binary and restart the service.

Step 2: Move from Redirect to TUN Mode (Crucial)

This is the single most important stability fix. Instead of messing with the router’s fragile iptables rules, TUN mode forces the router to spin up a virtual Layer 3 network interface. It handles traffic isolation cleanly and natively at the kernel layer.

  1. In the main menu, go to 4 模式选项 (Mode Options).
  2. Look for 运行模式 (Running Mode) or 进阶模式 (Advanced Mode).
  3. Switch the setting to TUN 模式 (TUN Mode) or TProxy 模式.
  • Note: TUN mode increases CPU utilization slightly because it processes packets via software routing, but the RT-AX88U’s quad-core chip can easily shoulder this load without sweating.

Step 3: Implement an Automatic Memory Flush

Because embedded Linux setups struggle to reclaim memory from long-running Go processes, we want to proactively clear the slate before the system runs out of RAM.

  1. From the main crash menu, select 6 定时任务 (Cron Jobs).
  2. Enable a 定时重启服务 (Scheduled Service Restart).
  3. Set it to trigger daily at an unnoticeable hour (e.g., 4:00 AM).

This doesn’t reboot your entire router; it simply restarts the proxy daemon, dropping memory usage back to base levels in less than 2 seconds.

The Alternative Path: Is it Time to Flash Merlin?

If you implement the steps above and still experience instability, the ultimate bottleneck is the stock ASUS operating system itself.

Because the RT-AX88U is a legendary enthusiast machine, it has Tier-1 support from Asuswrt-Merlin—a custom upstream fork of the official firmware.

Flashing Merlin is virtually risk-free because it retains the native ASUS bootloader and proprietary hardware acceleration drivers. However, it opens up a native Software Center allowing you to install customized, compiled proxy plugins (often utilizing Sing-box or native Mihomo backends). These plug-ins integrate directly into Merlin’s network stack far more smoothly than an automated SSH script ever could.

Summary Checklist for a Stable Edge Gateway

Before you consider spending money on an expensive x86 soft-router sidecar, run through this configuration checklist on your RT-AX88U:

  • Core: Mihomo (Clash-Meta) selected instead of stock Clash.
  • Inbound: TUN Mode enabled to isolate routing logic.
  • Maintenance: Daily 4:00 AM daemon restart configured via cron.
  • Protocol: Rely on modern node protocols (Vless-Reality, Hysteria 2), which drastically reduce packet overhead compared to legacy VMess.

By moving your routing to the kernel level with TUN mode and utilizing a modern core, your RT-AX88U can comfortably act as your sole, un-cluttered gatekeeper to the global web.