[95777] in RedHat Linux List
Re: Something blocking...?
daemon@ATHENA.MIT.EDU (Benjamin Han)
Wed Oct 21 08:41:26 1998
Date: Wed, 21 Oct 1998 08:42:10 -0400
From: Benjamin Han <dh6@acsu.buffalo.edu>
To: redhat-list@redhat.com
Resent-From: redhat-list@redhat.com
Reply-To: redhat-list@redhat.com
>No.. can you connect to DNS addresses? Sounds like you aren't bound to the
>DNS.
>if you have PPP going, but aren't bound to the DNS, then you can only
>connect to IPs... the other possibility is that you're behind a firewall.
>>I'm new to Linux, and this has puzzled me for a while. I could connect
>>PPP, but after that, I couldn't telnet/ftp back to my machine from
>>elsewhere. Sure I could telnet to the IP I'm assigned from my machine
>>(not using dumb ip address 127.0.0.1). Also I noticed that my LICQ
>>couldn't establish a 'direct connection' with others (must send messages
>>'thru server').
>>
>>My guess is there's something blocking any incoming 'logging'
>>requests... I don't even know if I call this right. Could someone give
>>me a hint? I'd appreciate that VERY MUCH.
Thanks for the tip. Sorry that I didn't make some points clear. As
mentioned in my post I'm using PPP to connect to the dial-up server in
our school. Given my dynamic IP address I can successfully nslookup to
get a name (which implies I did setup at least one DNS entry in
resolv.conf), but it's not the same with my real hostname (it's
something like ubppp-xxx-xxx.ppp-net.buffalo.edu where x is a numeral).
Using the name from nslookup I can also get its corresponding IP address
via nslookup. Of course my own hostname is made up by me, and no DNS
knows it.
As to the firewall theory, since I could successfully establish a
"direct connection" in ICQ under M$ Windows using the same PPP
connection (such as a chat session, or even IPhone talk), I don't think
that matters -- 'cause I can't even directly send a message via Licq
under Linux!
Some friend suggested that it has something to do with 'reverse
lookup.'I know little about this stuff -- does that mean that when you
access some server it will first check your FQDN via your IP
address, and then your IP address via the FQDN it got and see if they
match? If so, does it have anything to do with telnetting to my machine
from some other machine? Because if any 'reverse lookup' occurs, it must
be initiated by my machine?
BTW, I didn't try to login as root from remote machine -- I didn't go
that far. I 'telnet xxx.xxx.xxx.xxx' (IP address) and only saw 'trying
xxx.xxx.xxx.xxx...' hung forever.
System: RH 5.1 with kernel 2.0.34.
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