[ale] Need help reading tcpdump output

[Jim Philips]

Try running an ifconfig on your ppp0 interface with the cable modem and
with DSL. You may find that MTU is different depending on the device you
use to connect. I had major connection problenms with DSL a few weeks
ago. They all went away when I reduced MTU to 1474 from 1492.


On Thu, 2002-02-14 at 19:51, Gary MacKay wrote:
> I have a cable modem and a DSL line in my office. I use the cable modem
> to serve 'net access to my internal network and the DSL only has my
> email/web server on it. I am having problems sending email to a few
> domains, not all, just a few. I found I can telnet to port 25 of one of
> the failing domains via my cable modem, but not via the DSL line. Below
> are the first packett trace of each. The only thing I can see different
> is the flags SWE instead of just S. I do not know enough about the flags
> to know what that means nor how to fix it. The address I'm trying to
> send email to is 170.206.225.44.
> 
> --------DSL Line: fails
> 19:32:35.162544 207.87.222.229.15255 > 170.206.225.44.25: SWE
> 3747157433:3747157433(0) win 5840 <mss 1460,sackOK,timestamp 303797345
> 0,nop,wscale 0> (DF) [tos 0x10]
> 
> --------Cable modem: works
> 15:39:37.774455 11.22.33.44.41159 > 170.206.225.44.25: S
> 3934758720:3934758720(0) win 5840 <mss 1460,sackOK,timestamp 329647437
> 0,nop,wscale 0> (DF) [tos 0x10]
> 
> Both lines have a firewall with the exact same firewall rules, except
> for ports 25 and 110 on the DSL line. What am I missing?
> 
> - Gary
> 
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