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Thread: Setting MTU

  1. #1
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    Default Setting MTU

    Hi,

    My dsl connection works best if the mtu is set to 1400.

    The problem is although 1400 is already set as mtu value in network managaer it connects at 1492 which I found out by
    Code:
    ifconfig ppp0
    At 1492 some pages won't open at all so I do

    Code:
    sudo ifconfig ppp0 mtu 1400
    It stays at 1400 until I disconnect the dsl connection. Once I redial it again reverts back to 1492.

    How do I make 1400 as the permanent mtu value?

    Thanks in advance.
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  2. #2
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    Default Re: Setting MTU

    On 03/18/2011 10:06 PM, suse kid wrote:
    >
    > How do I make 1400 as the permanent mtu value?


    two ways:

    add/change MTU='1400' in /etc/sysconfig/network/ifcfg-ppp0 (*IF* it is
    that ppp0, if not, use different, maybe eth0)

    *OR*

    YaST => System => /etc/sysconfig Editor => Hardware => Network =>
    <Choose interface> (in this case ppp0) => MTU then type 1400 in the
    "Setting of MTU" at the top and then press OK

    --
    DenverD
    CAVEAT: http://is.gd/bpoMD
    [NNTP posted w/openSUSE 11.3, KDE4.5.5, Thunderbird3.1.8, nVidia
    173.14.28 3D, Athlon 64 3000+]
    "It is far easier to read, understand and follow the instructions than
    to undo the problems caused by not." DD 23 Jan 11

  3. #3

    Default Re: Setting MTU

    @suse_kid
    If I may, usually 1500 is the standard for DSL.
    You're connected PC to modem to DSL ?
    Modem doesn't have username, password, mtu for your DSL ISP?
    IIRC, you should be using mtu sizes in multiples of 16, ie, 1404, 1420, etc.
    Box 1: OpenSuse 11.1/Win7 | Linux 2.6.27 Gnome | AMD 64 X2 6000+ | nVidia 8600GT | 2GB RAM
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  4. #4
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    Default Re: Setting MTU

    Quote Originally Posted by DenverD View Post
    On 03/18/2011 10:06 PM, suse kid wrote:
    >
    > How do I make 1400 as the permanent mtu value?


    two ways:

    add/change MTU='1400' in /etc/sysconfig/network/ifcfg-ppp0 (*IF* it is
    that ppp0, if not, use different, maybe eth0)

    *OR*

    YaST => System => /etc/sysconfig Editor => Hardware => Network =>
    <Choose interface> (in this case ppp0) => MTU then type 1400 in the
    "Setting of MTU" at the top and then press OK

    --
    DenverD
    CAVEAT: C A V E A T
    [NNTP posted w/openSUSE 11.3, KDE4.5.5, Thunderbird3.1.8, nVidia
    173.14.28 3D, Athlon 64 3000+]
    "It is far easier to read, understand and follow the instructions than
    to undo the problems caused by not." DD 23 Jan 11
    Mainboard of my PC just went bad. I will apply your solution as soon as I replace it.

    Quote Originally Posted by tararpharazon View Post
    @suse_kid
    If I may, usually 1500 is the standard for DSL.
    You're connected PC to modem to DSL ?
    Modem doesn't have username, password, mtu for your DSL ISP?
    IIRC, you should be using mtu sizes in multiples of 16, ie, 1404, 1420, etc.

    No matter what mtu value I set it connects at 1492.
    Okay I will try 1404 instead of 1400.
    While downloading files from sites like rapidshare, etc if you don't have a premium account they impose a time gap between two downloads. So what I do is I simply disconnect & redial my dsl connection which renews my ip & I can then continue downloading the next file. If I configure my dsl connection using the modem's inbuilt dialer I have to restart the modem each time I want to renew my ip which reduces the life of modem/router in the long run. I have already lost a modem because of this reason. Therefore in my case a bridged connection is more appropriate.
    openSUSE Leap 15
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  5. #5

    Default Re: Setting MTU

    @suse_kid
    Ok, so you're using your DSL modem as a Dial up modem, by physically turning off the modem forcing it to obtain a new IP from it's DHCP server. Instead of patience? Chuckle, sorry.
    Why would that affect your MTU size?
    I think there's an issue with traffic through DSL connections that's supposed to improve QoS after being connected for a few days. Howeever you're changing the IP every 4hrs or so, maybe that's why you have trouble with some sites?
    Have you tried accessing the site with anonymous surfing? Tor, Jap?
    Box 1: OpenSuse 11.1/Win7 | Linux 2.6.27 Gnome | AMD 64 X2 6000+ | nVidia 8600GT | 2GB RAM
    Box 2: OpenSuse 11.2 | Linux 2.6.31 Gnome | AMD 64 3000+ | ATI X800 Pro | 1GB RAM
    Box 3: Win7 Premium Home | Intel P4 3.0Gz | ATI AIW 2006 | 2GB RAM

  6. #6
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    Default Re: Setting MTU

    Quote Originally Posted by tararpharazon View Post
    @suse_kid
    Ok, so you're using your DSL modem as a Dial up modem, by physically turning off the modem forcing it to obtain a new IP from it's DHCP server. Instead of patience?
    Chuckle, sorry.
    Why would that affect your MTU size?
    No. I used to do that. Now I don't physically turn off the modem. Instead I just disconnect my dsl connection using network manager & the connect again which renews my global which is provided by my ISP.

    Quote Originally Posted by tararpharazon View Post
    Have you tried accessing the site with anonymous surfing? Tor, Jap?
    This problem of some sites not opening is quite old. I guess it started approx. two years back. Yes, I tried proxy sites & the pages opened too. But I wanted a solution & not a workaround. After googling I got the idea of changing the mtu value & it worked. Now I just want to set the mtu value permanently. I will replace my mainboard within this week & write back what happens.

    Thanks.
    openSUSE Leap 15
    You aren't rich until you have something that money can't buy.

  7. #7
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    Default Re: Setting MTU

    I have purchase a new motherboard but I am facing a problem with openSUSE not loading.

    openSUSE 11.4 won't boot after installing new motherboard
    openSUSE Leap 15
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  8. #8
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    Default Re: Setting MTU

    Quote Originally Posted by DenverD View Post
    add/change MTU='1400' in /etc/sysconfig/network/ifcfg-ppp0 (*IF* it is
    that ppp0, if not, use different, maybe eth0)
    Logged in as root...then added MTU='1400' in /etc/sysconfig/network/ifcfg-eth0

    Didn't find any ppp0 there.

    Then logeed out of root account & logfed into my regular account
    but still mtu of eth0 is 1500 & that of ppp0 is 1492.
    openSUSE Leap 15
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  9. #9
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    Default Re: Setting MTU

    On 03/24/2011 08:06 PM, suse kid wrote:
    >
    > Logged in as root...then added MTU='1400' in
    > /etc/sysconfig/network/ifcfg-eth0
    >
    > Didn't find any ppp0 there.
    >
    > Then logeed out of root account& logfed into my regular account


    did you log into KDE, Gnome, LXDE or other desktop environment (which)
    as root and edit the listed file? and then log out, and log back in as
    yourself again??


    > but still mtu of eth0 is 1500& that of ppp0 is 1492.


    are you using a dial up modem or broadband over ethernet or what?


    --
    DenverD
    CAVEAT: http://is.gd/bpoMD
    [NNTP posted w/openSUSE 11.3, KDE4.5.5, Thunderbird3.1.8, nVidia
    173.14.28 3D, Athlon 64 3000+]
    "It is far easier to read, understand and follow the instructions than
    to undo the problems caused by not." DD 23 Jan 11

  10. #10
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    Default Re: Setting MTU

    Quote Originally Posted by DenverD View Post
    did you log into KDE, Gnome, LXDE or other desktop environment (which)
    as root and edit the listed file? and then log out, and log back in as
    yourself again??
    Yes, I
    1> logged into gnome as root
    2> edited the listed file
    3> then logged out from the root account
    4> logged back as myself
    5> then in terminal did su to become root then used ifconfig to find out the status of eth0 & ppp0

    Quote Originally Posted by DenverD View Post
    are you using a dial up modem or broadband over ethernet or what?
    I am using broadband over ethernet. I have configured my connection using network manager.
    So, I am quite surprised to find no such file as ppp0 in /etc/sysconfig/network/.

    Its ppp0's mtu which I wish to change not eth0's.
    openSUSE Leap 15
    You aren't rich until you have something that money can't buy.

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