PPPoE on WAN gets down randomly 19.07.2

Hello,

I am using following system:

Model: TP-Link Archer C7 v5
Architecture: Qualcomm Atheros QCA956X ver 1 rev 0
Firmware Version: OpenWrt 19.07.2 r10947-65030d81f3 / LuCI openwrt-19.07 branch git-20.064.69776-e8c638c
Kernel Version: 4.14.171

There is an industrial wifi that my router connected to which gets me a fiber connection on other end. My service supplier is telling me that there is no wifi drops on their logs at all. On the other hand, my log has following:

Tue Apr 21 16:10:42 2020 daemon.info dnsmasq-dhcp[2002]: DHCPREQUEST(br-lan) 192.168.8.215 c8:f7:33:5b:5c:98
Tue Apr 21 16:10:42 2020 daemon.info dnsmasq-dhcp[2002]: DHCPACK(br-lan) 192.168.8.215 c8:f7:33:5b:5c:98 SAMSUNG
Tue Apr 21 16:19:10 2020 daemon.info dnsmasq-dhcp[2002]: DHCPREQUEST(br-lan) 192.168.8.159 6c:56:97:b2:68:56
Tue Apr 21 16:19:10 2020 daemon.info dnsmasq-dhcp[2002]: DHCPACK(br-lan) 192.168.8.159 6c:56:97:b2:68:56 amazon-ab848d41e
Tue Apr 21 16:22:36 2020 daemon.info pppd[932]: No response to 5 echo-requests
Tue Apr 21 16:22:36 2020 daemon.notice pppd[932]: Serial link appears to be disconnected.
Tue Apr 21 16:22:36 2020 daemon.info pppd[932]: Connect time 31.1 minutes.
Tue Apr 21 16:22:36 2020 daemon.info pppd[932]: Sent 13760323 bytes, received 74112586 bytes.
Tue Apr 21 16:22:36 2020 daemon.notice netifd: Network device 'pppoe-wan' link is down
Tue Apr 21 16:22:36 2020 daemon.notice netifd: Interface 'wan' has lost the connection
Tue Apr 21 16:22:36 2020 daemon.warn dnsmasq[2002]: no servers found in /tmp/resolv.conf.auto, will retry
Tue Apr 21 16:22:39 2020 daemon.notice pppd[932]: Connection terminated.
Tue Apr 21 16:22:39 2020 daemon.info pppd[932]: Sent PADT
Tue Apr 21 16:22:39 2020 daemon.info pppd[932]: Exit.
Tue Apr 21 16:22:39 2020 daemon.notice netifd: Interface 'wan' is now down
Tue Apr 21 16:22:39 2020 daemon.notice netifd: Interface 'wan' is disabled
Tue Apr 21 16:22:39 2020 daemon.notice netifd: Interface 'wan6' is disabled
Tue Apr 21 16:22:39 2020 daemon.notice netifd: Interface 'wan' is enabled
Tue Apr 21 16:22:39 2020 daemon.notice netifd: Interface 'wan' is setting up now
Tue Apr 21 16:22:39 2020 daemon.notice netifd: Interface 'wan6' is enabled
Tue Apr 21 16:22:39 2020 daemon.err insmod: module is already loaded - slhc
Tue Apr 21 16:22:39 2020 daemon.err insmod: module is already loaded - ppp_generic
Tue Apr 21 16:22:39 2020 daemon.err insmod: module is already loaded - pppox
Tue Apr 21 16:22:39 2020 daemon.err insmod: module is already loaded - pppoe
Tue Apr 21 16:22:39 2020 daemon.info pppd[1146]: Plugin rp-pppoe.so loaded.
Tue Apr 21 16:22:39 2020 daemon.info pppd[1146]: RP-PPPoE plugin version 3.8p compiled against pppd 2.4.7
Tue Apr 21 16:22:39 2020 daemon.notice pppd[1146]: pppd 2.4.7 started by root, uid 0
Tue Apr 21 16:22:39 2020 daemon.info pppd[1146]: PPP session is 25825
Tue Apr 21 16:22:39 2020 daemon.warn pppd[1146]: Connected to 00:0c:42:9b:4f:5f via interface eth0.2
Tue Apr 21 16:22:39 2020 kern.info kernel: [414985.563210] pppoe-wan: renamed from ppp0
Tue Apr 21 16:22:39 2020 daemon.info pppd[1146]: Renamed interface ppp0 to pppoe-wan
Tue Apr 21 16:22:39 2020 daemon.info pppd[1146]: Using interface pppoe-wan
Tue Apr 21 16:22:39 2020 daemon.notice pppd[1146]: Connect: pppoe-wan <--> eth0.2
Tue Apr 21 16:22:39 2020 daemon.notice pppd[1146]: CHAP authentication succeeded
Tue Apr 21 16:22:39 2020 daemon.notice pppd[1146]: peer from calling number 00:0C:42:9B:4F:5F authorized
Tue Apr 21 16:22:40 2020 daemon.notice pppd[1146]: local  IP address 10.40.0.199
Tue Apr 21 16:22:40 2020 daemon.notice pppd[1146]: remote IP address 10.40.0.1
Tue Apr 21 16:22:40 2020 daemon.notice pppd[1146]: primary   DNS address 213.194.110.17
Tue Apr 21 16:22:40 2020 daemon.notice pppd[1146]: secondary DNS address 8.8.8.8
Tue Apr 21 16:22:40 2020 daemon.notice netifd: Network device 'pppoe-wan' link is up
Tue Apr 21 16:22:40 2020 daemon.notice netifd: Interface 'wan' is now up
Tue Apr 21 16:22:40 2020 daemon.info dnsmasq[2002]: reading /tmp/resolv.conf.auto
Tue Apr 21 16:22:40 2020 daemon.info dnsmasq[2002]: using local addresses only for domain test
Tue Apr 21 16:22:40 2020 daemon.info dnsmasq[2002]: using local addresses only for domain onion
Tue Apr 21 16:22:40 2020 daemon.info dnsmasq[2002]: using local addresses only for domain localhost
Tue Apr 21 16:22:40 2020 daemon.info dnsmasq[2002]: using local addresses only for domain local
Tue Apr 21 16:22:40 2020 daemon.info dnsmasq[2002]: using local addresses only for domain invalid
Tue Apr 21 16:22:40 2020 daemon.info dnsmasq[2002]: using local addresses only for domain bind
Tue Apr 21 16:22:40 2020 daemon.info dnsmasq[2002]: using local addresses only for domain lan
Tue Apr 21 16:22:40 2020 daemon.info dnsmasq[2002]: using nameserver 213.194.110.17#53
Tue Apr 21 16:22:40 2020 daemon.info dnsmasq[2002]: using nameserver 8.8.8.8#53
Tue Apr 21 16:22:40 2020 user.notice firewall: Reloading firewall due to ifup of wan (pppoe-wan)
Tue Apr 21 16:35:50 2020 daemon.info pppd[1146]: No response to 5 echo-requests
Tue Apr 21 16:35:50 2020 daemon.notice pppd[1146]: Serial link appears to be disconnected.
Tue Apr 21 16:35:50 2020 daemon.info pppd[1146]: Connect time 13.2 minutes.
Tue Apr 21 16:35:50 2020 daemon.info pppd[1146]: Sent 23881625 bytes, received 130807004 bytes.
Tue Apr 21 16:35:50 2020 daemon.notice netifd: Network device 'pppoe-wan' link is down
Tue Apr 21 16:35:50 2020 daemon.notice netifd: Interface 'wan' has lost the connection
Tue Apr 21 16:35:50 2020 daemon.warn dnsmasq[2002]: no servers found in /tmp/resolv.conf.auto, will retry
Tue Apr 21 16:35:53 2020 daemon.notice pppd[1146]: Connection terminated.
Tue Apr 21 16:35:53 2020 daemon.info pppd[1146]: Sent PADT
Tue Apr 21 16:35:53 2020 daemon.info pppd[1146]: Exit.
Tue Apr 21 16:35:53 2020 daemon.notice netifd: Interface 'wan' is now down
Tue Apr 21 16:35:53 2020 daemon.notice netifd: Interface 'wan' is disabled
Tue Apr 21 16:35:53 2020 daemon.notice netifd: Interface 'wan6' is disabled
Tue Apr 21 16:35:53 2020 daemon.notice netifd: Interface 'wan' is enabled
Tue Apr 21 16:35:53 2020 daemon.notice netifd: Interface 'wan' is setting up now
Tue Apr 21 16:35:53 2020 daemon.notice netifd: Interface 'wan6' is enabled
Tue Apr 21 16:35:53 2020 daemon.err insmod: module is already loaded - slhc
Tue Apr 21 16:35:53 2020 daemon.err insmod: module is already loaded - ppp_generic
Tue Apr 21 16:35:54 2020 daemon.err insmod: module is already loaded - pppox
Tue Apr 21 16:35:54 2020 daemon.err insmod: module is already loaded - pppoe
Tue Apr 21 16:35:54 2020 daemon.info pppd[1362]: Plugin rp-pppoe.so loaded.
Tue Apr 21 16:35:54 2020 daemon.info pppd[1362]: RP-PPPoE plugin version 3.8p compiled against pppd 2.4.7
Tue Apr 21 16:35:54 2020 daemon.notice pppd[1362]: pppd 2.4.7 started by root, uid 0
Tue Apr 21 16:35:54 2020 daemon.info pppd[1362]: PPP session is 26321
Tue Apr 21 16:35:54 2020 daemon.warn pppd[1362]: Connected to 00:0c:42:9b:4f:5f via interface eth0.2
Tue Apr 21 16:35:54 2020 kern.info kernel: [415779.971909] pppoe-wan: renamed from ppp0
Tue Apr 21 16:35:54 2020 daemon.info pppd[1362]: Renamed interface ppp0 to pppoe-wan
Tue Apr 21 16:35:54 2020 daemon.info pppd[1362]: Using interface pppoe-wan
Tue Apr 21 16:35:54 2020 daemon.notice pppd[1362]: Connect: pppoe-wan <--> eth0.2
Tue Apr 21 16:35:54 2020 daemon.notice pppd[1362]: CHAP authentication succeeded
Tue Apr 21 16:35:54 2020 daemon.notice pppd[1362]: peer from calling number 00:0C:42:9B:4F:5F authorized
Tue Apr 21 16:35:54 2020 daemon.notice pppd[1362]: local  IP address 10.40.0.199
Tue Apr 21 16:35:54 2020 daemon.notice pppd[1362]: remote IP address 10.40.0.1
Tue Apr 21 16:35:54 2020 daemon.notice pppd[1362]: primary   DNS address 213.194.110.17
Tue Apr 21 16:35:54 2020 daemon.notice pppd[1362]: secondary DNS address 8.8.8.8
Tue Apr 21 16:35:54 2020 daemon.notice netifd: Network device 'pppoe-wan' link is up
Tue Apr 21 16:35:54 2020 daemon.notice netifd: Interface 'wan' is now up
Tue Apr 21 16:35:54 2020 daemon.info dnsmasq[2002]: reading /tmp/resolv.conf.auto
Tue Apr 21 16:35:54 2020 daemon.info dnsmasq[2002]: using local addresses only for domain test
Tue Apr 21 16:35:54 2020 daemon.info dnsmasq[2002]: using local addresses only for domain onion
Tue Apr 21 16:35:54 2020 daemon.info dnsmasq[2002]: using local addresses only for domain localhost
Tue Apr 21 16:35:54 2020 daemon.info dnsmasq[2002]: using local addresses only for domain local
Tue Apr 21 16:35:54 2020 daemon.info dnsmasq[2002]: using local addresses only for domain invalid
Tue Apr 21 16:35:54 2020 daemon.info dnsmasq[2002]: using local addresses only for domain bind
Tue Apr 21 16:35:54 2020 daemon.info dnsmasq[2002]: using local addresses only for domain lan
Tue Apr 21 16:35:54 2020 daemon.info dnsmasq[2002]: using nameserver 213.194.110.17#53
Tue Apr 21 16:35:54 2020 daemon.info dnsmasq[2002]: using nameserver 8.8.8.8#53
Tue Apr 21 16:35:55 2020 user.notice firewall: Reloading firewall due to ifup of wan (pppoe-wan)

I am not sure when that drops occur. I feel them mostly when I am doing Remote Desktop Connection, TeamViewer Connection and similar. However it is not limited just with such. I suspect it goes down on Skype video meetings, and watching Youtube videos too.

I have identified following drops in my log so far:

	Line 17: Tue Apr 21 16:22:36 2020 daemon.notice netifd: Network device 'pppoe-wan' link is down
	Line 65: Tue Apr 21 16:35:50 2020 daemon.notice netifd: Network device 'pppoe-wan' link is down
	Line 113: Tue Apr 21 17:28:27 2020 daemon.notice netifd: Network device 'pppoe-wan' link is down
	Line 195: Tue Apr 21 18:13:14 2020 daemon.notice netifd: Network device 'pppoe-wan' link is down
	Line 254: Tue Apr 21 18:45:27 2020 daemon.notice netifd: Network device 'pppoe-wan' link is down
	Line 312: Tue Apr 21 19:33:00 2020 daemon.notice netifd: Network device 'pppoe-wan' link is down
	Line 398: Tue Apr 21 21:34:41 2020 daemon.notice netifd: Network device 'pppoe-wan' link is down
	Line 454: Tue Apr 21 22:13:33 2020 daemon.notice netifd: Network device 'pppoe-wan' link is down
	Line 505: Tue Apr 21 22:36:02 2020 daemon.notice netifd: Network device 'pppoe-wan' link is down
	Line 564: Tue Apr 21 22:44:45 2020 daemon.notice netifd: Network device 'pppoe-wan' link is down
	Line 630: Wed Apr 22 00:10:58 2020 daemon.notice netifd: Network device 'pppoe-wan' link is down
	Line 765: Wed Apr 22 11:08:59 2020 daemon.notice netifd: Network device 'pppoe-wan' link is down

There seems to be no fixed amount of time between drops.

I have already read several threads about this specific problem. None of them seems to have a solution. Owners of these threads stopped responding at some point. It is not clear if something has helped them or they gave up and reverted back to stock firmware of their devices. I do hope that I can fix it on my device.

My WAN interface settings are as following:
LCP echo failure threshold: 0 (default)
LCP echo interval: 5 (default)

I appreciate any help.

Thanks & regards,
Ertan

No response to 5 echo-requests

fwiw, have you tried setting:

LCP echo failure threshold: 5

If memory serves me right, setting it to '0' does Not have the desired effect of having an infinite tiimeout imho. This is known issue since LEDE 17 with xrx200 modem-routers like Home Hub 5A.

According to the user guide, this doesn't have default values.

keepalive 2 numbers no (none) The numbers must be separated by a space.
First number is for “seconds between each ping” ( ppp 's lcp-echo-interval option).
Second number is “we assume the connection is down after this number of pings failed” ( ppp 's lcp-echo-failure option).

In any case, since there is no regular cycle of interface restarts I doubt it is that.
Check the line for errors ip -s link show pppoe-wan and the interface ip -s link show ethX and the MTU

I have just changed

LCP echo failure treshold: 5

Will see if that helps.

I have put (default) because I did not modify these values. BTW, ip -s link show pppoe-wan gives me error ip link show pppoe-wan works. I am not so good at ip usage anyway.

Here is ip addr show output:

root@OpenWrt:~# ip addr show
1: lo: <LOOPBACK,UP,LOWER_UP> mtu 65536 qdisc noqueue state UNKNOWN qlen 1000
    link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00
    inet 127.0.0.1/8 scope host lo
       valid_lft forever preferred_lft forever
    inet6 ::1/128 scope host
       valid_lft forever preferred_lft forever
2: eth0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc fq_codel state UP qlen 1000
    link/ether ac:84:c6:8d:fe:3f brd ff:ff:ff:ff:ff:ff
    inet6 fe80::ae84:c6ff:fe8d:fe3f/64 scope link
       valid_lft forever preferred_lft forever
4: ifb0: <BROADCAST,NOARP> mtu 1500 qdisc noop state DOWN qlen 32
    link/ether b6:81:f4:61:47:5d brd ff:ff:ff:ff:ff:ff
5: ifb1: <BROADCAST,NOARP> mtu 1500 qdisc noop state DOWN qlen 32
    link/ether 0a:e6:00:66:c7:28 brd ff:ff:ff:ff:ff:ff
6: wlan0: <BROADCAST,MULTICAST> mtu 1500 qdisc noop state DOWN qlen 1000
    link/ether ac:84:c6:8d:fe:3e brd ff:ff:ff:ff:ff:ff
13: br-lan: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc noqueue state UP qlen 1000
    link/ether ac:84:c6:8d:fe:3f brd ff:ff:ff:ff:ff:ff
    inet 192.168.8.1/24 brd 192.168.8.255 scope global br-lan
       valid_lft forever preferred_lft forever
    inet6 fd91:8a85:4db7::1/60 scope global
       valid_lft forever preferred_lft forever
    inet6 fe80::ae84:c6ff:fe8d:fe3f/64 scope link
       valid_lft forever preferred_lft forever
14: eth0.1@eth0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc noqueue master br-lan state UP qlen 1000
    link/ether ac:84:c6:8d:fe:3f brd ff:ff:ff:ff:ff:ff
16: wlan1: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc noqueue master br-lan state UP qlen 1000
    link/ether ac:84:c6:8d:fe:3f brd ff:ff:ff:ff:ff:ff
    inet6 fe80::ae84:c6ff:fe8d:fe3f/64 scope link
       valid_lft forever preferred_lft forever
367: eth0.2@eth0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc noqueue state UP qlen 1000
    link/ether ac:84:c6:8d:fe:3f brd ff:ff:ff:ff:ff:ff
    inet6 fe80::ae84:c6ff:fe8d:fe3f/64 scope link
       valid_lft forever preferred_lft forever
368: pppoe-wan: <POINTOPOINT,MULTICAST,NOARP,UP,LOWER_UP> mtu 1480 qdisc fq_codel state UNKNOWN qlen 3
    link/ppp
    inet 10.40.0.199 peer 10.40.0.1/32 scope global pppoe-wan
       valid_lft forever preferred_lft forever
root@OpenWrt:~#

Here is ip link show output:

root@OpenWrt:~# ip link show
1: lo: <LOOPBACK,UP,LOWER_UP> mtu 65536 qdisc noqueue state UNKNOWN qlen 1000
    link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00
2: eth0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc fq_codel state UP qlen 1000
    link/ether ac:84:c6:8d:fe:3f brd ff:ff:ff:ff:ff:ff
4: ifb0: <BROADCAST,NOARP> mtu 1500 qdisc noop state DOWN qlen 32
    link/ether b6:81:f4:61:47:5d brd ff:ff:ff:ff:ff:ff
5: ifb1: <BROADCAST,NOARP> mtu 1500 qdisc noop state DOWN qlen 32
    link/ether 0a:e6:00:66:c7:28 brd ff:ff:ff:ff:ff:ff
6: wlan0: <BROADCAST,MULTICAST> mtu 1500 qdisc noop state DOWN qlen 1000
    link/ether ac:84:c6:8d:fe:3e brd ff:ff:ff:ff:ff:ff
13: br-lan: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc noqueue state UP qlen 1000
    link/ether ac:84:c6:8d:fe:3f brd ff:ff:ff:ff:ff:ff
14: eth0.1@eth0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc noqueue master br-lan state UP qlen 1000
    link/ether ac:84:c6:8d:fe:3f brd ff:ff:ff:ff:ff:ff
16: wlan1: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc noqueue master br-lan state UP qlen 1000
    link/ether ac:84:c6:8d:fe:3f brd ff:ff:ff:ff:ff:ff
367: eth0.2@eth0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc noqueue state UP qlen 1000
    link/ether ac:84:c6:8d:fe:3f brd ff:ff:ff:ff:ff:ff
368: pppoe-wan: <POINTOPOINT,MULTICAST,NOARP,UP,LOWER_UP> mtu 1480 qdisc fq_codel state UNKNOWN qlen 3
    link/ppp
root@OpenWrt:~#

I have no idea what I need to see here as an error. MTU information is in output though.

Thanks.

Post here the uci export network and ifconfig
MTU shows 1480, while it is expected to be 1492.

uci export network output (username and password masked):

root@OpenWrt:~# uci export network
package network

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

config globals 'globals'
        option ula_prefix 'fd91:8a85:4db7::/48'

config interface 'lan'
        option type 'bridge'
        option ifname 'eth0.1'
        option proto 'static'
        option netmask '255.255.255.0'
        option ip6assign '60'
        option ipaddr '192.168.8.1'

config interface 'wan'
        option ifname 'eth0.2'
        option proto 'pppoe'
        option username '<my_username>'
        option password '<my_password>'
        option ipv6 'auto'
        option keepalive '5 1'

config interface 'wan6'
        option ifname 'eth0.2'
        option proto 'pppoe'
        option username '<my_username>'
        option password '<my_password>'
        option ipv6 'auto'
        option auto '0'

config switch
        option name 'switch0'
        option reset '1'
        option enable_vlan '1'

config switch_vlan
        option device 'switch0'
        option vlan '1'
        option ports '2 3 4 5 0t'

config switch_vlan
        option device 'switch0'
        option vlan '2'
        option ports '1 0t'

root@OpenWrt:~#

ifconfig output:

root@OpenWrt:~# ifconfig
br-lan    Link encap:Ethernet  HWaddr AC:84:C6:8D:FE:3F
          inet addr:192.168.8.1  Bcast:192.168.8.255  Mask:255.255.255.0
          inet6 addr: fd91:8a85:4db7::1/60 Scope:Global
          inet6 addr: fe80::ae84:c6ff:fe8d:fe3f/64 Scope:Link
          UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
          RX packets:23686305 errors:0 dropped:0 overruns:0 frame:0
          TX packets:34597115 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:1000
          RX bytes:3354776983 (3.1 GiB)  TX bytes:42949428120 (39.9 GiB)

eth0      Link encap:Ethernet  HWaddr AC:84:C6:8D:FE:3F
          inet6 addr: fe80::ae84:c6ff:fe8d:fe3f/64 Scope:Link
          UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
          RX packets:51847403 errors:0 dropped:0 overruns:0 frame:0
          TX packets:32724737 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:1000
          RX bytes:195826624 (186.7 MiB)  TX bytes:893543806 (852.1 MiB)
          Interrupt:4

eth0.1    Link encap:Ethernet  HWaddr AC:84:C6:8D:FE:3F
          UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
          RX packets:7976530 errors:0 dropped:403 overruns:0 frame:0
          TX packets:9710404 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:1000
          RX bytes:1196886737 (1.1 GiB)  TX bytes:9963749068 (9.2 GiB)

eth0.2    Link encap:Ethernet  HWaddr AC:84:C6:8D:FE:3F
          inet6 addr: fe80::ae84:c6ff:fe8d:fe3f/64 Scope:Link
          UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
          RX packets:626826 errors:0 dropped:4666 overruns:0 frame:0
          TX packets:287022 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:1000
          RX bytes:502910429 (479.6 MiB)  TX bytes:63168006 (60.2 MiB)

lo        Link encap:Local Loopback
          inet addr:127.0.0.1  Mask:255.0.0.0
          inet6 addr: ::1/128 Scope:Host
          UP LOOPBACK RUNNING  MTU:65536  Metric:1
          RX packets:8792 errors:0 dropped:0 overruns:0 frame:0
          TX packets:8792 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:1000
          RX bytes:1063580 (1.0 MiB)  TX bytes:1063580 (1.0 MiB)

pppoe-wan Link encap:Point-to-Point Protocol
          inet addr:10.40.0.199  P-t-P:10.40.0.1  Mask:255.255.255.255
          UP POINTOPOINT RUNNING NOARP MULTICAST  MTU:1480  Metric:1
          RX packets:366396 errors:0 dropped:0 overruns:0 frame:0
          TX packets:282373 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:3
          RX bytes:424385660 (404.7 MiB)  TX bytes:56815527 (54.1 MiB)

wlan1     Link encap:Ethernet  HWaddr AC:84:C6:8D:FE:3F
          inet6 addr: fe80::ae84:c6ff:fe8d:fe3f/64 Scope:Link
          UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
          RX packets:16906171 errors:0 dropped:0 overruns:0 frame:0
          TX packets:26805655 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:1000
          RX bytes:3227277416 (3.0 GiB)  TX bytes:34650686133 (32.2 GiB)

root@OpenWrt:~#

In config change keepalive to 6 10. The 5 1 is too tight, after one failure it will consider the link down.
Other than that you have 4666 dropped packets on the eth0.2 interface.
Check if there are drops also on the modem.
Check if the cables are good and replace them just in case if you can.
Verify with your ISP that the MTU 1480 is correct indeed.

1 Like

OK, I changed keepalive to 6 10

eth0.2 is set on both WAN and WAN6 I do not know if WAN6 it is necessary at all. It is not autostarting. It is not runngin (Stop button below is disabled). I cannot remember clearly but likely it is defined by LUCI when I set PPPoE. I might be wrong about that though. It is possible packet drops on eth0.2 might be on that WAN6.

When you say if any drops on modem, my modem is a wifi placed outside at the roof. My ISP telling me there is no downtime/disconnects in their logs in terms of signal communication between wifi on my side and wifi on their side. I am not specifically informed of any packet drops, unfortunately. Meaning if there are drops on modem, I am not aware of it.

It is really not easy to replace cabling. Another thing I should mention is OpenWrt modem reach is thru a switch (TP-SF10008D). There is two cables connected to that switch, One from OpenWrt and one from outside WiFi antenna.

OpenWrt <---> Switch <---> Modem <---> ISP Fiber line

I am trying to get confirmation about MTU. Hope they can get back to me soon.

Thanks.

I cannot get a feedback from my ISP, is there any harm if I manually set MTU 1492?

After setting keepalive 6 10 aka LCP echo failure threshold: 6 , LCP echo interval: 10

I did not see and feel any link down so far. I am going to continue to check closely for any "link is down" messages in system log for about a week more and report back in here.

Try to skip a payment, they'll contact you :stuck_out_tongue:

It could make things worse if 1480 is indeed right.

It's easier to look at the connection uptime.

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Update: I did not have any link down for almost 6 days. It seems keepalive setting helped my problem.
Thanks to all helped.

Now, I wonder if changing MTU from 1480 to 1492 will have negative affect on the performance. Thing is I do not know how to figure if it is better or worse (except if link down problem emerges again).

Is there a way/tool to measure if increasing MTU helps/worsens overall performance?

Thanks & regards,
Ertan

You can try some tests to calculate the optimal MTU.
https://kb.netgear.com/19863/Ping-Test-to-determine-Optimal-MTU-Size-on-Router
https://www.linksys.com/us/support-article?articleNum=134914

My ping results are not fragmenting if packet size is 1452.
As we sites advise calculation 1452+28=1480

It turns out MTU 1480 actually is the correct value.

Thank you.

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If your problem is solved, please consider marking this topic as [Solved]. See How to mark a topic as [Solved] for a short how-to.

If you did not first change MTU to 1492 before running this tests, these results are bogus. The entire point of the test is to find the largest frame size that is able to traverse the connection to the destination. If you still have your router's MTU set to 1480 then of course 1452 is going to be the largest ping you can do before your packet gets fragmented. What you want to do, is increase your MTU to 1492 (I would actually even try 1500 to be honest, since some ISPs support baby jumbo frames for PPPoE connections. Mine does for example). And THEN rerun the test and see when your ISP starts fragmenting your packets. Once you know that, you can set your MTU to match your ISP's MTU.

Edit: If you want to try baby jumbo frames, you need to realize that PPPoE itself has a 8 byte overhead. So in order to get a MTU of 1500 inside the point-to-point tunnel, you need a MTU of 1508 outside the tunnel. In order to configure that, you need to set a MTU of 1508 on the underlying interface:

config interface 'eth0'
	option ifname 'eth0'
	option proto 'none'
	option mtu '1508'

And put the 1500 MTU for the PPPoE connection on top of that interface (VLAN 6 for me). Note that you actually have to include the 8 byte overhead here, so you will also select a MTU of 1508 here:

config interface 'wan'
	option proto 'pppoe'
	option password 'redacted'
	option ipv6 'auto'
	option username 'redacted'
	option mtu '1508'
	option ifname 'eth0.6'

Make sure you set MTU to 1500 for things like your LAN and/or guest networks, because otherwise they will use the MTU of the underlying interface and be at 1508 as well. A good way to test is to see what ifconfig returns after configuring everything. It should have a 1508 MTU on the ethernet device, 1508 on the VLAN on top of this interface and 1500 MTU on the tunnel itself. Furthermore, the lan bridge and/or guest lan bridge should again have a 1500 MTU.

If this is all too complicated just stick with a 1492 MTU inside your tunnel (so 1500 MTU on the underlying interface) to test and don't employ baby jumbo frames. There's a good chance the ISP doesn't even support it. But definitely try at least 1492!

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Even I override my pppoe-wan MTU to 1492, it stays at 1480.

Below is my ifconfig output after overriding pppoe-wan to 1492 in LUCI and applying changes

root@OpenWrt:~# ifconfig 
br-lan    Link encap:Ethernet  HWaddr AC:84:C6:8D:FE:3F  
          inet addr:192.168.8.1  Bcast:192.168.8.255  Mask:255.255.255.0
          inet6 addr: fd91:8a85:4db7::1/60 Scope:Global
          inet6 addr: fe80::ae84:c6ff:fe8d:fe3f/64 Scope:Link
          UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
          RX packets:56998908 errors:0 dropped:0 overruns:0 frame:0
          TX packets:77346189 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:1000 
          RX bytes:12762321861 (11.8 GiB)  TX bytes:89521613111 (83.3 GiB)

eth0      Link encap:Ethernet  HWaddr AC:84:C6:8D:FE:3F  
          inet6 addr: fe80::ae84:c6ff:fe8d:fe3f/64 Scope:Link
          UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
          RX packets:128291692 errors:0 dropped:0 overruns:0 frame:0
          TX packets:86520354 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:1000 
          RX bytes:3595895728 (3.3 GiB)  TX bytes:3855550171 (3.5 GiB)
          Interrupt:4 

eth0.1    Link encap:Ethernet  HWaddr AC:84:C6:8D:FE:3F  
          UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
          RX packets:26797516 errors:0 dropped:3304 overruns:0 frame:0
          TX packets:31435006 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:1000 
          RX bytes:8475014986 (7.8 GiB)  TX bytes:28677949441 (26.7 GiB)

eth0.2    Link encap:Ethernet  HWaddr AC:84:C6:8D:FE:3F  
          inet6 addr: fe80::ae84:c6ff:fe8d:fe3f/64 Scope:Link
          UP BROADCAST RUNNING MULTICAST  MTU:1492  Metric:1
          RX packets:2532 errors:0 dropped:7 overruns:0 frame:0
          TX packets:627 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:1000 
          RX bytes:2643762 (2.5 MiB)  TX bytes:112511 (109.8 KiB)

lo        Link encap:Local Loopback  
          inet addr:127.0.0.1  Mask:255.0.0.0
          inet6 addr: ::1/128 Scope:Host
          UP LOOPBACK RUNNING  MTU:65536  Metric:1
          RX packets:69976 errors:0 dropped:0 overruns:0 frame:0
          TX packets:69976 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:1000 
          RX bytes:7606297 (7.2 MiB)  TX bytes:7606297 (7.2 MiB)

pppoe-wan Link encap:Point-to-Point Protocol  
          inet addr:10.40.0.199  P-t-P:10.40.0.1  Mask:255.255.255.255
          UP POINTOPOINT RUNNING NOARP MULTICAST  MTU:1480  Metric:1
          RX packets:2112 errors:0 dropped:0 overruns:0 frame:0
          TX packets:611 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:3 
          RX bytes:2527965 (2.4 MiB)  TX bytes:97880 (95.5 KiB)

wlan1     Link encap:Ethernet  HWaddr AC:84:C6:8D:FE:3F  
          inet6 addr: fe80::ae84:c6ff:fe8d:fe3f/64 Scope:Link
          UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
          RX packets:32304753 errors:0 dropped:0 overruns:0 frame:0
          TX packets:49758076 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:1000 
          RX bytes:6088269316 (5.6 GiB)  TX bytes:63861333168 (59.4 GiB)

This is, I think, most likely due to eth0.2 (physical interface for pppoe-wan) having MTU size of 1492.

I failed to find relevant page in LUCI to change eth0.2 MTU value. I do not know using cli for changing certain configurations. Forum search did not help me much.

Below is my /etc/config/network file

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

config globals 'globals'
        option ula_prefix 'fd91:8a85:4db7::/48'

config interface 'lan'
        option type 'bridge'
        option ifname 'eth0.1'
        option proto 'static'
        option netmask '255.255.255.0'
        option ip6assign '60'
        option ipaddr '192.168.8.1'

config interface 'wan'
        option ifname 'eth0.2'
        option proto 'pppoe'
        option username 'username'
        option password 'password'
        option ipv6 'auto'
        option keepalive '6 10'
        option mtu '1492'

config interface 'wan6'
        option ifname 'eth0.2'
        option proto 'pppoe'
        option username 'username'
        option password 'password'
        option ipv6 'auto'
        option auto '0'

config switch
        option name 'switch0'
        option reset '1'
        option enable_vlan '1'

config switch_vlan
        option device 'switch0'
        option vlan '1'
        option ports '2 3 4 5 0t'

config switch_vlan
        option device 'switch0'
        option vlan '2'
        option ports '1 0t'

I appreciate any help on changing eth0.2 MTU value either on LUCI or thru cli.

Thanks & regards.

Create a new Interface with eth0.2 and set it to DHCP or Static as your modem allows and then you can change the MTU for it.

I am not sure that I understood correctly. Below is my current interfaces screen

And my /etc/config/network output:

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

config globals 'globals'
        option ula_prefix 'fd91:8a85:4db7::/48'

config interface 'lan'
        option type 'bridge'
        option ifname 'eth0.1'
        option proto 'static'
        option netmask '255.255.255.0'
        option ip6assign '60'
        option ipaddr '192.168.8.1'

config interface 'wan'
        option ifname 'eth0.2'
        option proto 'pppoe'
        option username 'username'
        option password 'password'
        option ipv6 'auto'
        option keepalive '6 10'
        option mtu '1492'
        option force_link '1'

config interface 'wan6'
        option proto 'pppoe'
        option username 'username'
        option password 'password'
        option ipv6 'auto'
        option auto '0'
        option ifname 'eth0.2'
        option mtu '1492'

config switch
        option name 'switch0'
        option reset '1'
        option enable_vlan '1'

config switch_vlan
        option device 'switch0'
        option vlan '1'
        option ports '2 3 4 5 0t'

config switch_vlan
        option device 'switch0'
        option vlan '2'
        option ports '1 0t'

config interface 'eth0_2'
        option ifname 'eth0.2'
        option proto 'dhcp'
        option mtu '1500'

It appear in my config files that I have set new eth0_2 interface to mtu 1500, my wan interface to 1492. However my ifconfig output claims eth0_2 interface is 1492 and my wan interface is 1480. It is not helping to tick "Force link" in settings as it is already ticked for both of these interfaces.

My ifconfig output:

br-lan    Link encap:Ethernet  HWaddr AC:84:C6:8D:FE:3F  
          inet addr:192.168.8.1  Bcast:192.168.8.255  Mask:255.255.255.0
          inet6 addr: fd91:8a85:4db7::1/60 Scope:Global
          inet6 addr: fe80::ae84:c6ff:fe8d:fe3f/64 Scope:Link
          UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
          RX packets:57543755 errors:0 dropped:0 overruns:0 frame:0
          TX packets:78130838 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:1000 
          RX bytes:13249412251 (12.3 GiB)  TX bytes:89975147486 (83.7 GiB)

eth0      Link encap:Ethernet  HWaddr AC:84:C6:8D:FE:3F  
          inet6 addr: fe80::ae84:c6ff:fe8d:fe3f/64 Scope:Link
          UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
          RX packets:129855926 errors:0 dropped:0 overruns:0 frame:0
          TX packets:87792911 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:1000 
          RX bytes:328887082 (313.6 MiB)  TX bytes:478709217 (456.5 MiB)
          Interrupt:4 

eth0.1    Link encap:Ethernet  HWaddr AC:84:C6:8D:FE:3F  
          UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
          RX packets:27302196 errors:0 dropped:3327 overruns:0 frame:0
          TX packets:32182642 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:1000 
          RX bytes:8955665165 (8.3 GiB)  TX bytes:29098243568 (27.0 GiB)

eth0.2    Link encap:Ethernet  HWaddr AC:84:C6:8D:FE:3F  
          inet6 addr: fe80::ae84:c6ff:fe8d:fe3f/64 Scope:Link
          UP BROADCAST RUNNING MULTICAST  MTU:1492  Metric:1
          RX packets:7516 errors:0 dropped:62 overruns:0 frame:0
          TX packets:3432 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:1000 
          RX bytes:2132859 (2.0 MiB)  TX bytes:1137014 (1.0 MiB)

lo        Link encap:Local Loopback  
          inet addr:127.0.0.1  Mask:255.0.0.0
          inet6 addr: ::1/128 Scope:Host
          UP LOOPBACK RUNNING  MTU:65536  Metric:1
          RX packets:79144 errors:0 dropped:0 overruns:0 frame:0
          TX packets:79144 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:1000 
          RX bytes:8473213 (8.0 MiB)  TX bytes:8473213 (8.0 MiB)

pppoe-wan Link encap:Point-to-Point Protocol  
          inet addr:10.40.0.199  P-t-P:10.40.0.1  Mask:255.255.255.255
          UP POINTOPOINT RUNNING NOARP MULTICAST  MTU:1480  Metric:1
          RX packets:2447 errors:0 dropped:0 overruns:0 frame:0
          TX packets:2782 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:3 
          RX bytes:834028 (814.4 KiB)  TX bytes:873085 (852.6 KiB)

wlan1     Link encap:Ethernet  HWaddr AC:84:C6:8D:FE:3F  
          inet6 addr: fe80::ae84:c6ff:fe8d:fe3f/64 Scope:Link
          UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
          RX packets:32385656 errors:0 dropped:0 overruns:0 frame:0
          TX packets:49847070 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:1000 
          RX bytes:6120637745 (5.7 GiB)  TX bytes:63925552189 (59.5 GiB)

Edit: Interesting thing is here it is suggested to remove bridge and work with two subnets? I could not see how to test it in my system.