Cannot set ppp0's MTU to 1500

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dnl
Posts: 375
Joined: June 28th, 2013, 11:03 am

Cannot set ppp0's MTU to 1500

Post by dnl » February 21st, 2018, 10:23 am

Hi,

I've been troubleshooting my internet connection and noticed a MTU mismatch. My ISP assures me that I do not need to have an MTU lower than 1500, however IPFire keeps setting ppp0 to 1492. (I don't and won't ever use a VPN)
I can't find anything on the wiki and nothing in the forums in English.

I'm connecting with PPPoE and have tried;
  1. Setting the MTU in the "Dial Up" profile (pppsetup page), then reconnecting
  2. Manually setting

    Code: Select all

    RED_DHCP_FORCE_MTU=1500
    in /var/ipfire/ethernet/settings, then reconnecting
    (based on how MTU is set in /var/ipfire/dhcpc/dhcpcd-hooks/10-mtu)
but the MTU keeps being set to 1492.

Am I missing something?

Thank you in advance!
IPFire 2.x (Latest Update) on x86_64 Intel Bay Trail CPU, 4GiB RAM, RED + GREEN + BLUE + ORANGE

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Deepcuts
Posts: 461
Joined: March 1st, 2016, 3:18 pm
Location: Romania

Re: Cannot set ppp0's MTU to 1500

Post by Deepcuts » February 21st, 2018, 4:48 pm

deleted

later edit: I just now realized that you might want to set the MTU on ppp0 and not red0, so what i wrote previously is a no go.
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dnl
Posts: 375
Joined: June 28th, 2013, 11:03 am

Re: Cannot set ppp0's MTU to 1500

Post by dnl » February 24th, 2018, 3:21 am

Thanks for that!
I'll try it now.

EDIT: Oh I read your response in the email notification before this edit. Thanks anyway!
I didn't find the script, but I'm sure IPFire is automatically subtracting 8 bytes for the PPPoE headers. I'll double check with my ISP.
IPFire 2.x (Latest Update) on x86_64 Intel Bay Trail CPU, 4GiB RAM, RED + GREEN + BLUE + ORANGE

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