[UCIMC-Tech] Re: Gmail problems

[David Young]

On Thu, Jun 26, 2008 at 10:19:49PM -0500, Barry Isralewitz wrote:
>   Here I have one Firefox tab Firefox open, with a google attempt a couple of minutes, and another tab with a google contact in the process of failing.
> 
> bash2-2.05b$     netstat -tf inet
> Active Internet connections
> Proto Recv-Q Send-Q  Local Address          Foreign Address        (state)
> tcp4       0    392  192.168.42.106.53676   od-in-f83.google.http  ESTABLISHED
> tcp4       0      0  192.168.42.106.61635   209.62.185.9.http      ESTABLISHED
> tcp4       0      0  192.168.42.106.59502   204.2.228.81.http      ESTABLISHED
> tcp4       0      0  192.168.42.106.56346   128.242.191.49.http    ESTABLISHED
> tcp4       0      0  192.168.42.106.49924   winnipeg.ks.uiuc.ssh   ESTABLISHED
> tcp4       0      0  192.168.42.106.49986   winnipeg.ks.uiuc.ssh   ESTABLISHED

Is there a firewall in the loop?  Which firewall?  Any DNS
proxying/caching?

TCPDump or WireShark can help to shed light on a problem like this.
For example, you can capture all of the HTTP traffic in a file using
tcpdump,

	tcpdump -w http.cap -i interface-name 'src or dst port http'

You can find out the interface-name to use like this,

> route -n get www.google.com
   route to: 64.233.167.104
destination: default
       mask: default
    gateway: 64.198.255.1
 local addr: 64.198.255.10
  interface: wm0
      flags: <UP,GATEWAY,DONE,STATIC>
 recvpipe  sendpipe  ssthresh  rtt,msec    rttvar  hopcount      mtu     expire
       0         0         0         0         0         0         0         0

(I'm running NetBSD, but FreeBSD is similar.)  My interface is wm0.

You can use WireShark (best) or TCPDump (adequate) to examine the traffic
you captured, later.  I can help interpret the results.

Dave

-- 
David Young             OJC Technologies
dyoung at ojctech.com      Urbana, IL * (217) 278-3933 ext 24