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PPPoE Possible MTU Issues

Posted: Tue Jan 22, 2019 9:50 pm
by flynno
Hey guys,

I have a LHG XL 5 ac with ROS package v6.42.11 on clients premises.
LHG XL 5 ac upgraded with v6.42.11
Client speed is set to 20M download 5M upload download but cannot pass 10MB on the speedtest.net app or website.

Bandwidth tests from CPE to Main router show 20M download 5 Upload, so no issue with speeds to the main router.
Client has issues with working remotely and testing download speeds using app or website.

TX / RX signal Strength -55/-52 dBm
CCQ 80/83 %
Protocol 802.11
5745/20-Ceee/ac(33dBm)
Noise Floor -105 dBm
Signal to Noise 52 dB

Wireless Interface
Wireless MTU 1524 << This is normally set 1500 on other CPE's
L2 MTU 1600

Wireless is in station mode connected to Remote Site AP
CPE connects with pppoe over the wireless interface

PPPoE is WAN
ether1 is LAN DHCP 192.168.88.1/24

PPPoE Status on CPE
MTU 1480
MRU 1504 (It automatic sets to 1504 not sure why, I have changed it to 1480 but still same results)
PPP Profile Change TCP MSS set to yes

Main Router PPPoE Server
Change TCP MSS set to yes
Queue Type set to wireless-default

I have tried using mangle rule below but still same issues
chain=forward action=change-mss new-mss=clamp-to-pmtu passthrough=yes tcp-flags=syn protocol=tcp

Anyone having similar problem with any solution?


Thanks in advance

Re: PPPoE Possible MTU Issues

Posted: Tue Jan 22, 2019 10:25 pm
by CZFan
Have you checked the client's Ethernet sync speed?

Re: PPPoE Possible MTU Issues

Posted: Tue Jan 22, 2019 10:33 pm
by flynno
Hey CZFan,

I forgot to mention that it also goes lower than 10MB also, so it's a high 10M - 11M or can be as low as 3M etc... but never higher than 12M

Re: PPPoE Possible MTU Issues

Posted: Tue Jan 22, 2019 11:14 pm
by CZFan
Can you provide a diagram of network, note on drawing where client is and where data is that he is downloading?

Just want to see where the possible problem areas might be

Re: PPPoE Possible MTU Issues

Posted: Wed Jan 23, 2019 12:46 am
by flynno
Ok see image of network, R4 is router that client is connected to that is having the speed issues

Re: PPPoE Possible MTU Issues

Posted: Thu Jan 24, 2019 3:53 pm
by CZFan
If speed varies, then I doubt it is ethernet syc related.

Majority of problems experienced with MPLS, etc is usually MTU related, but what I would suggest is go and have a cup of coffee with the client, then test from his connection and capture / sniff some packets to see if any excessive fragmentation occurs, etc. and take it from there