IPv6 pings fail on 5GHz radio only on Linksys MX4200v2

grahamalama · January 8, 2025, 7:16pm

My main router is a Linksys MX4200v2 running 24.10.0-rc5. I have all three radios enabled (2.4GHz, 5GHz, and 6 GHz), for now with different SSIDs for debugging purposes.

On the 5GHz network, ping6 2001:4860:4860::8888 doesn't return any packets. When I first reboot the router, I get:

> ping6 2001:4860:4860::8888
ping6: connect: Network is unreachable

but after some time, I start getting:

> ping6 2001:4860:4860::8888
PING 2001:4860:4860::8888(2001:4860:4860::8888) 56 data bytes

which hangs for a while, then I'll kill and see 100% packet loss

^C
--- 2001:4860:4860::8888 ping statistics ---
3 packets transmitted, 0 received, 100% packet loss, time 2083ms

However, I get packets back on the 2.4 and 6 radios.

For some extra debugging context, I have this kind of setup in my home, and pings work when I connect to both the the 2.4GHz and 5GHz networks on the access point.

Any ideas what's happening here?

brada4 · January 9, 2025, 12:15am

can you ping -6 openwrt.lan. ?

Please connect to your OpenWrt device using ssh and copy the output of the following commands and post it here using the "Preformatted text </> " button:

Remember to redact passwords, MAC addresses and any public IP addresses you may have:

ubus call system board
cat /etc/config/network
cat /etc/config/wireless
cat /etc/config/dhcp
cat /etc/config/firewall

grahamalama · January 9, 2025, 1:49am

can you ping -6 openwrt.lan.

Yep! It appears I can.

Here's the combined output of:

ubus call system board
cat /etc/config/network
cat /etc/config/wireless
cat /etc/config/dhcp
cat /etc/config/firewall

Output

{
        "kernel": "6.6.69",
        "hostname": "OpenWrt",
        "system": "ARMv8 Processor rev 4",
        "model": "Linksys MX4200v2",
        "board_name": "linksys,mx4200v2",
        "rootfs_type": "squashfs",
        "release": {
                "distribution": "OpenWrt",
                "version": "24.10.0-rc5",
                "revision": "r28304-6dacba30a7",
                "target": "qualcommax/ipq807x",
                "description": "OpenWrt 24.10.0-rc5 r28304-6dacba30a7",
                "builddate": "1736026537"
        }
}

config interface 'loopback'
        option device 'lo'
        option proto 'static'
        option ipaddr '127.0.0.1'
        option netmask '255.0.0.0'

config globals 'globals'
        option ula_prefix 'xxxx:xxxx:xxxx::/48'

config device
        option name 'br-lan'
        option type 'bridge'
        list ports 'lan1'
        list ports 'lan2'
        list ports 'lan3'

config device
        option name 'lan1'
        option macaddr 'XX:XX:XX:XX:XX:XX'

config device
        option name 'lan2'
        option macaddr 'XX:XX:XX:XX:XX:XX'

config device
        option name 'lan3'
        option macaddr 'XX:XX:XX:XX:XX:XX'

config interface 'lan'
        option device 'br-lan'
        option proto 'static'
        option ipaddr '192.168.1.1'
        option netmask '255.255.255.0'
        option ip6assign '60'

config device
        option name 'wan'
        option macaddr 'XX:XX:XX:XX:XX:XX'

config interface 'wan'
        option device 'wan'
        option proto 'dhcp'

config interface 'wan6'
        option device 'wan'
        option proto 'dhcpv6'

config interface 'vpn1'
        option proto 'wireguard'
        option private_key 'XXXXXXXXXXXXXXXXXXXXXXXX'
        option listen_port '51820'
        list addresses '10.1.99.1/24'

config wireguard_vpn1
        option description 'A'
        option public_key 'XXXXXXXXXXXXXXXXXXXXXXXX'
        list allowed_ips '10.1.99.20/32'
        option persistent_keepalive '25'

config wireguard_vpn1
        option description 'B'
        option public_key 'XXXXXXXXXXXXXXXXXXXXXXXX'
        list allowed_ips '10.1.99.21/32'
        option persistent_keepalive '25'

config wireguard_vpn1
        option description 'C'
        option public_key 'XXXXXXXXXXXXXXXXXXXXXXXX'
        list allowed_ips '10.1.99.22/32'
        option persistent_keepalive '25'


config wifi-device 'radio0'
        option type 'mac80211'
        option path 'platform/soc@0/c000000.wifi'
        option band '5g'
        option channel 'auto'
        option htmode 'HE80'
        option cell_density '0'

config wifi-iface 'default_radio0'
        option device 'radio0'
        option network 'lan'
        option mode 'ap'
        option ssid 'My SSID (5)'
        option encryption 'psk2'
        option key 'XXXXXXXXXXXXXXXXXXX'

config wifi-device 'radio1'
        option type 'mac80211'
        option path 'platform/soc@0/c000000.wifi+1'
        option band '2g'
        option channel '1'
        option htmode 'HE20'
        option cell_density '0'

config wifi-iface 'default_radio1'
        option device 'radio1'
        option network 'lan'
        option mode 'ap'
        option ssid 'My SSID (2.4)'
        option encryption 'psk2'
        option key 'XXXXXXXXXXXXXXXXXXX'
        option macfilter 'deny'
        list maclist 'XX:XX:XX:XX:XX:XX'

config wifi-device 'radio2'
        option type 'mac80211'
        option path 'platform/soc@0/c000000.wifi+2'
        option band '5g'
        option channel 'auto'
        option htmode 'HE80'
        option cell_density '0'

config wifi-iface 'default_radio2'
        option device 'radio2'
        option mode 'ap'
        option ssid 'My SSID (6)'
        option encryption 'psk2'
        option key 'XXXXXXXXXXXXXXXXXXX'
        option network 'lan'


config dnsmasq
        option domainneeded '1'
        option localise_queries '1'
        option rebind_protection '1'
        option rebind_localhost '1'
        option local '/lan/'
        option domain 'lan'
        option expandhosts '1'
        option cachesize '1000'
        option authoritative '1'
        option readethers '1'
        option leasefile '/tmp/dhcp.leases'
        option resolvfile '/tmp/resolv.conf.d/resolv.conf.auto'
        option localservice '1'
        option ednspacket_max '1232'

config dhcp 'lan'
        option interface 'lan'
        option start '100'
        option limit '150'
        option leasetime '12h'
        option dhcpv4 'server'
        option dhcpv6 'server'
        option ra 'server'
        option ra_slaac '1'
        list ra_flags 'managed-config'
        list ra_flags 'other-config'

config dhcp 'wan'
        option interface 'wan'
        option ignore '1'

config odhcpd 'odhcpd'
        option maindhcp '0'
        option leasefile '/tmp/hosts/odhcpd'
        option leasetrigger '/usr/sbin/odhcpd-update'
        option loglevel '4'

config host
        option name 'A'
        option ip '192.168.1.118'
        list mac 'XX:XX:XX:XX:XX:XX'

config host
        option name 'B'
        option ip '192.168.1.124'
        list mac 'XX:XX:XX:XX:XX:XX'

config host
        option name 'C'
        option ip '192.168.1.134'
        list mac 'XX:XX:XX:XX:XX:XX'

config host
        option name 'D'
        option ip '192.168.1.223'
        list mac 'XX:XX:XX:XX:XX:XX'

config host
        option name 'E'
        option ip '192.168.1.237'
        list mac 'XX:XX:XX:XX:XX:XX'


config defaults
        option input 'ACCEPT'
        option output 'ACCEPT'
        option forward 'REJECT'
        option synflood_protect '1'

config zone
        option name 'lan'
        option input 'ACCEPT'
        option output 'ACCEPT'
        option forward 'ACCEPT'
        list network 'lan'

config zone
        option name 'wan'
        option input 'REJECT'
        option output 'ACCEPT'
        option forward 'REJECT'
        option masq '1'
        option mtu_fix '1'
        list network 'wan'
        list network 'wan6'

config forwarding
        option src 'lan'
        option dest 'wan'

config rule
        option name 'Allow-DHCP-Renew'
        option src 'wan'
        option proto 'udp'
        option dest_port '68'
        option target 'ACCEPT'
        option family 'ipv4'

config rule
        option name 'Allow-Ping'
        option src 'wan'
        option proto 'icmp'
        option icmp_type 'echo-request'
        option family 'ipv4'
        option target 'ACCEPT'

config rule
        option name 'Allow-IGMP'
        option src 'wan'
        option proto 'igmp'
        option family 'ipv4'
        option target 'ACCEPT'

config rule
        option name 'Allow-DHCPv6'
        option src 'wan'
        option proto 'udp'
        option dest_port '546'
        option family 'ipv6'
        option target 'ACCEPT'

config rule
        option name 'Allow-MLD'
        option src 'wan'
        option proto 'icmp'
        option src_ip 'fe80::/10'
        list icmp_type '130/0'
        list icmp_type '131/0'
        list icmp_type '132/0'
        list icmp_type '143/0'
        option family 'ipv6'
        option target 'ACCEPT'

config rule
        option name 'Allow-ICMPv6-Input'
        option src 'wan'
        option proto 'icmp'
        list icmp_type 'echo-request'
        list icmp_type 'echo-reply'
        list icmp_type 'destination-unreachable'
        list icmp_type 'packet-too-big'
        list icmp_type 'time-exceeded'
        list icmp_type 'bad-header'
        list icmp_type 'unknown-header-type'
        list icmp_type 'router-solicitation'
        list icmp_type 'neighbour-solicitation'
        list icmp_type 'router-advertisement'
        list icmp_type 'neighbour-advertisement'
        option limit '1000/sec'
        option family 'ipv6'
        option target 'ACCEPT'

config rule
        option name 'Allow-ICMPv6-Forward'
        option src 'wan'
        option dest '*'
        option proto 'icmp'
        list icmp_type 'echo-request'
        list icmp_type 'echo-reply'
        list icmp_type 'destination-unreachable'
        list icmp_type 'packet-too-big'
        list icmp_type 'time-exceeded'
        list icmp_type 'bad-header'
        list icmp_type 'unknown-header-type'
        option limit '1000/sec'
        option family 'ipv6'
        option target 'ACCEPT'

config rule
        option name 'Allow-IPSec-ESP'
        option src 'wan'
        option dest 'lan'
        option proto 'esp'
        option target 'ACCEPT'

config rule
        option name 'Allow-ISAKMP'
        option src 'wan'
        option dest 'lan'
        option dest_port '500'
        option proto 'udp'
        option target 'ACCEPT'

config redirect
        option dest 'lan'
        option target 'DNAT'
        option name 'vpn'
        option src 'wan'
        option src_dport '51820'
        option dest_ip '192.168.1.1'
        option dest_port '51820'
        list proto 'tcp'
        list proto 'udp'

config zone
        option name 'vpn'
        option input 'ACCEPT'
        option output 'ACCEPT'
        option forward 'REJECT'
        list network 'vpn1'

config rule
        option name 'Cameras'
        list proto 'all'
        option src 'lan'
        list src_mac 'XX:XX:XX:XX:XX:XX'
        option dest 'wan'
        option target 'REJECT'

config forwarding
        option src 'vpn'
        option dest 'lan'

config forwarding
        option src 'vpn'
        option dest 'wan'

config forwarding
        option src 'lan'
        option dest 'vpn'