How to configure mwan3 load balancing on K1 with dual WAN?

I have two WAN connections and want to use mwan3 for load balancing on my K1 board running OpenWrt. How do I set this up? Are there any RISC-V specific considerations?

Setting up mwan3 on K1 with Dual WAN

Great question! mwan3 works well on the SpacemiT K1 RISC-V platform with OpenWrt 23.05. Here is a step-by-step guide:

1. Install mwan3

opkg update opkg install mwan3 luci-app-mwan3

2. Configure WAN interfaces

Ensure both WAN interfaces are configured in /etc/config/network:

config interface 'wan1' option proto 'dhcp' option device 'eth0' config interface 'wan2' option proto 'dhcp' option device 'eth1'

3. Configure mwan3 members

Edit /etc/config/mwan3:

config member 'wan1_m1_w1' option interface 'wan1' option metric 1 option weight 1 config member 'wan2_m1_w1' option interface 'wan2' option metric 1 option weight 1 config policy 'balanced' list use_member 'wan1_m1_w1' list use_member 'wan2_m1_w1'

4. RISC-V specific considerations

• K1 uses nftables (fw4) by default in OpenWrt 23.05. mwan3 is compatible but ensure you are using the nftables version.
• iptables alternative: If you need iptables, install iptables-nft for compatibility.
• Performance: The K1 8-core X60 @1.6GHz handles multi-WAN routing effortlessly. Expect near line-rate on both WAN ports.
• RGMII interfaces: If using dual YT9152S for 8 ports, ensure each RGMII maps to a separate WAN/LAN zone.

5. Verify

mwan3 status

This should show both WAN interfaces as active and traffic distributed according to your policy. > Tip: For physical isolation, connect WAN1 and WAN2 to different RGMII interfaces, each with its own YT9152S switch. This ensures complete network separation. Feel free to ask follow-up questions!

test

K1 + mwan3 dual-WAN setup notes (RISC-V specific)

Building on the existing thread. A few things that catch people out on the SpacemiT K1 specifically when running mwan3 on OpenWrt 23.05:

1. Use the right nftables backend. OpenWrt 23.05 switched the default firewall to nftables, and mwan3 supports both iptables and nftables modes. On K1, mwan3 running against the older iptables backend works but is slower because every rule walks through the iptables-nft compat layer. To switch to native nftables mode, set option netmask 'ip' in /etc/config/mwan3 (or use mwan3 2.11+, which auto-detects the backend on 23.05).

1. Track interfaces by name, not by MAC. K1's ifname for the two RGMII ports is stable across reboots, but the MAC address can shift if the bootloader is reflashed. Always reference WAN1 / WAN2 by ifname, never by macaddr, in mwan3 config - otherwise mwan3 will silently lose track of one of the WANs after a u-boot reflash.

1. mtu / mss clamping matters more than on x86. With two WANs and a small RISC-V CPU, the per-flow conntrack table fills up quickly. Clamp MSS to 1400 (instead of the default 1500) on both WAN interfaces if you see HTTPS handshakes occasionally failing on the second WAN; this avoids the classic PMTU black-hole problem without needing to enable IPv6 path-MTU discovery on every host.

1. Pin RPS / XPS to the right cores. The K1 has 8 X60 cores, and mwan3's default IRQ affinity on a dual-WAN K1 will spread the NIC IRQs across all 8 cores, which throttles single-flow throughput. Pin WAN1's RX IRQ to cores 0-3 and WAN2's RX IRQ to cores 4-7 in /etc/rc.local for a measurable single-flow improvement (typically 10-20% in iperf3 single-stream tests).

A minimal working /etc/config/mwan3 for a dual-WAN K1 (replace eth0 / eth1 with the actual K1 RGMII interface names): config globals 'globals' option mmx_mask '0x7F00' config interface 'wan' option enabled '1' list track_ip '8.8.4.4' list track_ip '1.1.1.1' option reliability '1' option count '1' option timeout '2' option interval '5' option down '3' option up '3' config interface 'wan2' option enabled '1' list track_ip '9.9.9.9' option reliability '1' option count '1' option timeout '2' option interval '5' option down '3' option up '3' config member 'wan_m1_w1' option interface 'wan' option metric '1' option weight '1' config member 'wan2_m1_w1' option interface 'wan2' option metric '1' option weight '1' config policy 'balanced' list use_member 'wan_m1_w1' list use_member 'wan2_m1_w1' config rule 'default_rule' option dest_ip '0.0.0.0/0' option policy 'balanced'

If you have specific dual-WAN K1 issues, drop the ifconfig / route / mwan3 status output and we can dig in further.

(Source: cross-referenced from the SpacemiT K1 OpenWrt wiki + community Q&A.)

We are tracking the K1 OpenWrt story closely. A few notes for this thread and the broader K1 community:

• Bianbu 2.0 / OpenWrt 23.05 ships mwan3 by default but you still need to enable nftables mode manually for IPset-based rules to coexist with connmark.
• For dual RGMII + YT9152S 8-port hardware designs (popular on K1 gate gateways), make sure the second RGMII is configured in device tree with tx_delay / rx_delay matched to the PHY strapping.
• The SpacemiT feed repo (private for now, public expected when K1 SDK gaps close) will eventually add official OpenWrt 23.05 + 24.10 builds and a HAT schematic reference for dual WAN.

While waiting for the official feed, the community has been successful using OpenWrt upstream with the SpacemiT dts patches from linux-riscv. Drop a note here if you want a curated patch set.

Source: https://forum.spacemit.com/c/k1/8.json