ifconfig will show you the MTU for all interfaced. Ignore lo - that is very high
anyway. I found that I had to set the MTU on the ppp0 and eth0 interfaces to 296 to
make everything work properly. And for best results I have set the MTU on the nic in
the Win95 clients to 296 as well. To check the ISPs MTU if you can telnet to the ISP
and login to a shell prompt, do an ifconfig (you will probably have to specify the
full path 'casue users don't usually have /sbin or /usr/sbin (depending on the unix
flavour) in their path), and that should tell ya. My ISP is runnint Redhat Linux, so
that was easy. Also check the /var/adm/debug file for when pppd makes its connection.
You should see a couple of lines showing MRU negotiation requests. Here are a couple
of examples from mine. The first shows when negotiation takes place:
Jun 3 12:48:04 baldrick pppd[114]: sent [LCP ConfReq id=0x1 <mru 296> <magic
0x22005eef> <pcomp> <accomp>]
Jun 3 12:48:04 baldrick pppd[114]: rcvd [LCP ConfReq id=0x1 <mru 296> <auth pap>
<magic 0x3b4a5f18> <pcomp> <accomp>]
Jun 3 12:48:04 baldrick pppd[114]: sent [LCP ConfAck id=0x1 <mru 296> <auth pap>
<magic 0x3b4a5f18> <pcomp> <accomp>]
Jun 3 12:48:07 baldrick pppd[114]: sent [LCP ConfReq id=0x1 <mru 296> <magic
0x22005eef> <pcomp> <accomp>]
Jun 3 12:48:07 baldrick pppd[114]: rcvd [LCP ConfAck id=0x1 <mru 296> <magic
0x22005eef> <pcomp> <accomp>]
and this one shows when I disabled negotation (this connected, but transmission speeds
were slower and I could not browse some web pages, plus a couple of other email
servers could not communicate with baldrick, strange and varying symptoms):
May 28 19:35:55 baldrick pppd[632]: rcvd [LCP ConfReq id=0x1 <mru 296> <auth pap>
<magic 0x4ddd6066> <pcomp> <accomp>]
May 28 19:35:55 baldrick pppd[632]: sent [LCP ConfRej id=0x1 <mru 296>]
May 28 19:35:55 baldrick pppd[632]: rcvd [LCP ConfReq id=0x2 <auth pap> <magic
0x4ddd6066> <pcomp> <accomp>]
May 28 19:35:55 baldrick pppd[632]: sent [LCP ConfAck id=0x2 <auth pap> <magic
0x4ddd6066> <pcomp> <accomp>]
May 28 19:35:58 baldrick pppd[632]: sent [LCP ConfReq id=0x1 <magic 0xa747a992>
<pcomp> <accomp>]
May 28 19:35:58 baldrick pppd[632]: rcvd [LCP ConfAck id=0x1 <magic 0xa747a992>
<pcomp> <accomp>]
It doesn't matter if you have an MTU of 296 or 1500, as long as it is consistent
throughout. Our ISP says he did extensive testing when he was first setting himself
up and found that 296 was optimum for the sort of conditions he was operating in.
Can you ping from WinNT to something outside the Linux box ie. on the internet? I
tried that here and no masquerading entries appeared. As soon as I started an FTP
connection from Win95 an IP masquerading entry appeared.
Dave
----------
From: Jann Linder[SMTP:[EMAIL PROTECTED]]
Sent: Wednesday, 3 June 1998 16:27
To: 'Dave'
Cc: 'masq'
Subject: Re: [masq] ip masq connects best if constantly pinging clients
Where else do I set mtu's except for the pppd dialer (linux to the
'net)...and is there a good way of finding out the exact mtu? (the isp
doesn't know...their cust. svc is not tech support and they are a bit too
big to care about the little guy...problem is ..they are the only ricochet
modem ppp provider around San francisco) My ppp0 is defaulted to 1500 mtu
at i set the modem at a 57600 connection speed.
Yup...can ping linux from winnt and vice versa...currently i have a nohup
ping process going from the linux box to winnt (lotsa traffic...but only
two machines on the network anyway...so it really doesnt matter) This
pinging is allowing instant access to the net...
slow..but instant.
Jann
Jann Linder
Web Developer/CH2M Hill - SFO
[EMAIL PROTECTED]
Home Page:
http://www.jann.com/
CalendarPlus Web Site:
http://www.calendarplus.com/
-----Original Message-----
From: Dave [SMTP:[EMAIL PROTECTED]]
Sent: Tuesday, June 02, 1998 11:13 PM
To: 'masq'
Subject: Re: [masq] ip masq connects best if constantly pinging clients
Jann,
Can you ping anything outside your network from the WinNT box? From the
Linux box?
It may not help, but it's something else to check, but check the MTU
everywhere you can think of. I had some strange problems 'cause I had some
MTUs set differently.
We have a machine here with a flaky ethernet card. If I do a ping -f
<ip.addr> it drops about 5 packets a second. Not good. Maybe one of your
nic's is problematic?
Dave
----------
From: Jann Linder[SMTP:[EMAIL PROTECTED]]
Sent: Wednesday, 3 June 1998 15:45
To: 'Dave'; 'masq'
Subject: Re: [masq] ip masq connects best if constantly pinging clients
The only thing that makes me think this is not true is that I have netstat
-Mc running constantly and it is not listing any connections when this
occurs...the gateway in the client machines is listed as an ip # so i
wouldn't think this is a problem...
But...as they say, thanks for taking the time to think about it...it gives
food for thought.
Jann
Jann Linder
Web Developer/CH2M Hill - SFO
[EMAIL PROTECTED]
Home Page:
http://www.jann.com/
CalendarPlus Web Site:
http://www.calendarplus.com/
-----Original Message-----
From: Dave [SMTP:[EMAIL PROTECTED]]
Sent: Tuesday, June 02, 1998 5:34 PM
To: 'masq'
Subject: Re: [masq] ip masq connects best if constantly pinging clients
Greetings.
It might have something to do with DNS entries expiring perhaps. If you
keep pinging then possibly the DNS entries would stay there. If there was
no activity maybe the DNS entries would expire and be removed from the
cache.
I noticed that if my Linux machine (before I connected it to the network)
could not resolve a name locally it would try to contact the next higher
DNS, but not being connected could not, so it timeouted, but this took a
few seconds.
You can try doing a ipfwadm -M -l (lowercase ell) which will list the
masquerading entries, and show you the times those expire as well.
hth
Dave
----------
From: Jann Linder[SMTP:[EMAIL PROTECTED]]
Sent: Wednesday, 3 June 1998 10:18
To: 'masq'
Subject: [masq] ip masq connects best if constantly pinging clients
Anyone heard of IP Masquerade running on linux kernel 2.0.32 listening
closer if you continually ping a client machine?
my client is winnt and if i set linux to continually ping it, then the
linux box receives an acts on TCP requests from the winnt box
faster...sometimes it doesn't recognize the winnt box ax all...here are the
commands and routing i am using on the linux box.
> ipfwadm -F -f
> ipfwadm -F -p deny
> ipfwadm -F -a m -S 192.168.1.0/24 -D 0.0.0.0/0
Leaving out the Metric, Ref and Use as they would not tell you anything--
Destination Gateway Genmask Flags Iface
mg134-198.domain * 255.255.255.255 UH ppp0
192.168.1.0 * 255.255.255.0 U eth0
127.0.0.0 * 255.0.0.0 U lo
default mg134-198..domain 0.0.0.0 UG ppp0
Thanks in advance for advice.
Jann
(bad day!) ;(
Jann Linder
Web Developer/CH2M Hill - SFO
[EMAIL PROTECTED]
Home Page:
http://www.jann.com/
CalendarPlus Web Site:
http://www.calendarplus.com/
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