Did someone reload the internet from floppy last night?

[Kevin D. Clark]

Steven W. Orr writes:

> But what I'm trying
> to figure out for the future still remains: If in the future, an outside
> person tries to send me mail and gets connection refused, how can I run
> something which will tell me where along the way the connection was
> getting refused?

You are probably not going to be able to run a useful diagnostic on
your end of the connection.  Running a diagnostic from the other end
of the connection will probably be fruitful.

> At the time that I wanted to ask this question, I was able to both ping 
> and traceroute to myself from the outside. It was the refusal on my port 
> 25 that was the problem. RCN was claiming that they were not blocking my 
> 25 and I didn't believe them, but I had no way to prove otherwise.

Was "outside" in the previous snippet outside of RCN?

>  That's 
> why I'm looking for a way to see all the hops along the way but confined 
> to TCP on 25. If the internet was hosed over because of a big backbone 
> bankruptcy, and someone else was blocking my 25, that's different than if 
> RCN was doing it.
> 
> Also, while this was going on, there were a number of other SMTP servers 
> outside of RCN which would not respond to me when I tried to telnet out to 
> them.

Next time this happens, run the tcpdump command that I
suggested. Then, show us the output.

(actually, this might work better: 
    tcpdump 'host my-computer and ( tcp port 25 or icmp )'
)

--kevin
-- 
Kevin D. Clark / Cetacean Networks / Portsmouth, N.H. (USA)
cetaceannetworks.com!kclark (GnuPG ID: B280F24E)
alumni.unh.edu!kdc