Date: Mon, 28 Nov 2005 23:07:42 -0800 From: perikillo <perikillo@gmail.com> To: freebsd-questions@freebsd.org Subject: Re: FreeBSD 5.4-p8 PPPoE Link Problems...? Message-ID: <51d7a5160511282307o563bda65vf86a4240d26395a6@mail.gmail.com> In-Reply-To: <666bdb140511280018o67406684j@mail.gmail.com> References: <51d7a5160511272321o1f841d1epf1b947ce2c958b54@mail.gmail.com> <666bdb140511280018o67406684j@mail.gmail.com>
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On 11/28/05, Vladimir Tsvetkov <npacemo@gmail.com> wrote: > > Hi people. > > > > I have one ISP that give 512Kbps service, they give to me one > > modem SpeedStream, i setup everything, before this service was running > > on freebsd 4.11-p16(i think ...?), them change all to freebsd 5.4-p8. > > > > The problem here is that sometimes appear the link up: > > > > tun0: flags=3D8051<UP,POINTOPOINT,RUNNING,MULTICAST> mtu 1492 > > inet 201.143.64.40 --> 201.130.144.1 netmask 0xffffffff > > Opened by PID 236 > > > > But if i try to access the Internet, the browser say that i dont > > have connection, them i go to my freebsd box, test the connection with > > Ping and is correct i lost my connection, i need to manually force the > > link to close and again connect. > > > > I dont know if this problem is from my ISP or is Freebsd, i dont > > have a clue where to find the problem to fix this, with freebsd 4.11 i > > have this problems to. This is my /etc/rc.conf for ppp > > > > # User ppp configuration. > > ppp_enable=3D"YES" # Start user-ppp (or NO). > > ppp_mode=3D"ddial" # Choice of "auto", "ddial", "direct"= or "dedica > > ppp_nat=3D"NO" # Use PPP's internal network address translat= ion or NO. > > ppp_profile=3D"prodigy" # Which profile to use from /etc/ppp/ppp.conf= . > > ppp_user=3D"root" # Which user to run ppp as > > > > I was thinking to create a script that check every 5 minutes the > > link and do something to re-connect, but i dont think is the right > > solution. > > > > Does someone have any idea what can i do to find the problem and > > fix this...? > > > > FreeBSD 5.4-p8 > > Firewall IPFILTER > > > > I have everything enable on the kernel not from modules. > > > > Thanks all for your time. > > To me, this looks like a PPPoE and Path MTU Discovery Problem - for > the presentation of the problem you can read this (section 6.3) - > http://66.249.93.104/search?q=3Dcache:eOfdxb4tmkoJ:renaud.waldura.com/doc= /freebsd/pppoe/+Renaud+Waldura+%2B+PPPoE&hl=3Den&client=3Dfirefox-a. > > You should do the following to establish the Maximum Transmit Unit for > your connection: > > To see how big are the fragments of the TCP Packets I do the following: > > 1. Start tcpdump and ping something with big SMTP packets (I use the > maximum size for an Ethernet frame): > > [csh prompt]# tcpdump > tcpdump.dump > [csh prompt]# ping -s 1500 www.freebsd.org > > Packets with this size - 1500 bytes will be transmited not as a whole > packet - this packet will be chopped and transmited in few parts. > > 2. Lets look at an excerpt of the tcpdump file: > > vladimir.inana.org.1898 > 192.168.222.1.domain: 30781+ A? www.freebsd.or= g. (33) > vladimir.inana.org > www.freebsd.org: icmp: echo request (frag 1025:1472@= 0+) > vladimir.inana.org > www.freebsd.org: icmp (frag 1025:36@1472) > www.freebsd.org > vladimir.inana.org: icmp: echo reply (frag > 35040:1456@0+) [tos 0x16,ECT(0)] > www.freebsd.org > vladimir.inana.org: icmp (frag 35040:52@1456) [tos > 0x16,ECT(0)] > > We can see clearly that these big packets are splitted in two fragments: > > 36B + 1472B =3D 1508B =3D 1500B(Ethernet Frame) + 8B(PPPoE Additional Enc= apsulation) > > 3. I set the mtu in the my ppp.conf with the following value: > > 1472B + 8B =3D 1480B > > and my connection works correctly :) > > Good Luck :) > Vladimir T > Hi Vladimir. Look i setup my kernel for BPF, i test first with data size of 1500 and receive this after some minutes waiting answer: #ping -s 1500 cvsup4.FreeBSD.org <---My near server --after some minutes Ctrl+c 98 packets transmitted, 0 packets receive, 100% lost Them i star playing with the -s option and found that i can send packets no more than 1464 bytes. 1464+8 =3D 1472 this is my MTU If i send packets more than this quantity (1464) dont receive any answer from ping command. Before my MTU was 1492 on the /etc/ppp/ppp.conf because i use one example to setup my DSL modem, them to test i comment MTU and MRU and start playing with the values. I was reading the ppp man page, it says that the default value for MTU and MRU is 1500 bytes, but like i show you, i cannot send more than 1464+8, them i setup both values to 1472 on /etc/ppp/ppp.conf set MTU=3D1472 set MRU=3D1472 My conclusion is correct Vladimir...? Thanks for your time.
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