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Date:      Wed, 16 May 2001 08:19:27 -0700 (PDT)
From:      "Rodney W. Grimes" <freebsd@gndrsh.dnsmgr.net>
To:        jim@thehousleys.net (James Housley)
Cc:        freebsd-stable@FreeBSD.ORG
Subject:   Re: ppp problems on 4.3-RELEASE and PPPoE
Message-ID:  <200105161519.IAA09749@gndrsh.dnsmgr.net>
In-Reply-To: <3B028CDB.837B64D4@thehousleys.net> from James Housley at "May 16, 2001 10:21:15 am"

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Someplace along the network path between the client and server someone
is probably blocking icmp packets, and thus causing path MTU discovery
to fail.

You have a non standard MTU of 1492 on your PPP link, and without the
ICMP type 3, code 4 packets getting through the windblows box is going
to use an MTU of 1500.

Good luck in finding the person dropping ICMP type 3 packets in your
path, unless it happens to be you....

> I have been having problems with the the newer Windows machines, 2000 &
> Me, not being able to access some websites.  I have had to manually edit
> the registry to change the MTU.  This should not be needed, because I am
> running 4.3-RELEASE which has had the tcpmssfixup feature for a while. 
> It is enabled.  Unfortunately this maching is in an office in Canada,
> and I am not in Canada.  I am using natd and ipfw for NAT and the
> firewall.  The link has a static IP if it matters.  Below I am attaching
> ppp.conf.  I have watched some of the data with tcpdump on both tun0 and
> ed0, but I am not sure what to look for.
> 
> Suggestion on how to proceed.
> 
> Jim
> 
> ---- ppp.conf ----
> default:
>  ident user-ppp VERSION (built COMPILATIONDATE)
> 
>  # Ensure that "device" references the correct serial port
>  # for your modem. (cuaa0 = COM1, cuaa1 = COM2)
>  #
>  set device /dev/cuaa1
> 
>  set log Phase Chat LCP IPCP CCP tun command
>  set speed 115200
>  set dial "ABORT BUSY ABORT NO\\sCARRIER TIMEOUT 5 \
>            \"\" AT OK-AT-OK ATE1Q0 OK \\dATDT\\T TIMEOUT 40 CONNECT"
>  set ifaddr 10.0.0.1/0 10.0.0.2/0 255.255.255.0 0.0.0.0
>  set timeout 180                        # 3 minute idle timer (the
> default)
>  add default HISADDR                    # Add a (sticky) default route
>  enable dns                             # request DNS info (for
> resolv.conf)
> 
> magma:
>  ident
>  set device PPPoE:ed0
>  set MRU 1492
>  set MTU 1492
>  set authname **************
>  set authkey *******
>  set log Phase Chat Connect
>  set dial
>  set login
>  set ifaddr 10.0.0.1/0 10.0.0.2/0 0.0.0.0/0 0.0.0.0/0
>  set timeout 0
>  set server +3000 *******
>  enable tcpmssfixup
>  disable dns
>  set cd 5
>  set crtscts off
>  enable pap
>  disable pred1
> 
> ------------------
> -- 
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> jeh@FreeBSD.org      http://www.FreeBSD.org     The Power to Serve
> jim@TheHousleys.Net  http://www.TheHousleys.net
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> The wise man built his network upon Un*x.
>     The foolish man built his network upon Windows.
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-- 
Rod Grimes - KD7CAX @ CN85sl - (RWG25)               rgrimes@gndrsh.dnsmgr.net

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