No Route to Host errors without ICMP traffic

No Route to Host errors without ICMP traffic

Post by Donald E. Fo » Wed, 19 Jun 2002 04:57:05



I'm getting a no route to host error sporadically (about 4% of the
time in a 2 hour period) with connecting to a certain host in the UK.
I'm in the US.  When trying to track down where this is coming from, I
did a sniffer trace from my end and found that there are *no* ICMP
messages being received regarding this error.  How else could a tcp
socket open/send give me a "No Route to Host" message without having
received the ICMP telling it so?  (BTW, the host is blocking all ICMP
on its end.  I'm not.)

My configuration--Red Hat 7.2, single proc, kernel 2.4.7-10smp, x86
box with 512M ram.  The CPU is not all that busy and the system is not
loaded, there is plenty of RAM free, etc.

Donald E. Foss

 
 
 

No Route to Host errors without ICMP traffic

Post by Karl Heye » Wed, 19 Jun 2002 06:53:40



> I'm getting a no route to host error sporadically (about 4% of the
> time in a 2 hour period) with connecting to a certain host in the UK.
> I'm in the US.  When trying to track down where this is coming from, I
> did a sniffer trace from my end and found that there are *no* ICMP
> messages being received regarding this error.  How else could a tcp
> socket open/send give me a "No Route to Host" message without having
> received the ICMP telling it so?  (BTW, the host is blocking all ICMP
> on its end.  I'm not.)

without seeing the traffic around the point of failure it hards to say,
but ICMP can be issued from any point in the internet not just the end
machine.  Retransmissions should occur on timeouts at your end though.

karl.

 
 
 

No Route to Host errors without ICMP traffic

Post by Donald E. Fo » Wed, 19 Jun 2002 11:32:38


ICMP is not being issued from any point anywhere--that's the weird
part.  There is the originating SYN packet, the responding SYN/ACK,
then nothing else.  I would expect a TCP Timeout here or something
other than No Route to Host.  I have no rules blocking ICMP, and I'm
receiving other ICMP for other things.

Donald E. Foss



> > I'm getting a no route to host error sporadically (about 4% of the
> > time in a 2 hour period) with connecting to a certain host in the UK.
> > I'm in the US.  When trying to track down where this is coming from, I
> > did a sniffer trace from my end and found that there are *no* ICMP
> > messages being received regarding this error.  How else could a tcp
> > socket open/send give me a "No Route to Host" message without having
> > received the ICMP telling it so?  (BTW, the host is blocking all ICMP
> > on its end.  I'm not.)

> without seeing the traffic around the point of failure it hards to say,
> but ICMP can be issued from any point in the internet not just the end
> machine.  Retransmissions should occur on timeouts at your end though.

> karl.

 
 
 

No Route to Host errors without ICMP traffic

Post by wavema » Wed, 19 Jun 2002 17:03:33


A recent experiecne:
An ISP in Hong Kong has blocked the SMTP port (port 25) so that any customer
self setup mail server cannot send outgoing mail,
and in the mail queue, there are all queed message with "No Route to Host
errors",  I don't know whether this can help and hope it will.
Will it be likely that your ISP block some ports or the UK side blocked some
ports or hosts in your side?



Quote:> I'm getting a no route to host error sporadically (about 4% of the
> time in a 2 hour period) with connecting to a certain host in the UK.
> I'm in the US.  When trying to track down where this is coming from, I
> did a sniffer trace from my end and found that there are *no* ICMP
> messages being received regarding this error.  How else could a tcp
> socket open/send give me a "No Route to Host" message without having
> received the ICMP telling it so?  (BTW, the host is blocking all ICMP
> on its end.  I'm not.)

> My configuration--Red Hat 7.2, single proc, kernel 2.4.7-10smp, x86
> box with 512M ram.  The CPU is not all that busy and the system is not
> loaded, there is plenty of RAM free, etc.

> Donald E. Foss

 
 
 

No Route to Host errors without ICMP traffic

Post by Karl Heye » Wed, 19 Jun 2002 22:41:18



> ICMP is not being issued from any point anywhere--that's the weird
> part.  There is the originating SYN packet, the responding SYN/ACK,
> then nothing else.  I would expect a TCP Timeout here or something
> other than No Route to Host.  I have no rules blocking ICMP, and I'm
> receiving other ICMP for other things.

With a TCP connection there needs to be another ACK after the ones you
have stated before the connection is established.  If _you_ are
initiating the connection then your not sending the ACK, which maybe
due to firewall rules.

ping on the other hand is based on ICMP not TCP so the TCP timeout/
retransmissions don't come into play, but the ping will timeout and
display the message if their is no reply at all.

karl.

 
 
 

No Route to Host errors without ICMP traffic

Post by Donald E. Fo » Thu, 20 Jun 2002 03:53:09


What you were seeing is a ICMP type 3C, port unreachable.  In my case,
there is no ICMP message at all.  Also, the traffic is going to a web
server and other sessions on the same box are working fine.

Donald E. Foss


> A recent experiecne:
> An ISP in Hong Kong has blocked the SMTP port (port 25) so that any customer
> self setup mail server cannot send outgoing mail,
> and in the mail queue, there are all queed message with "No Route to Host
> errors",  I don't know whether this can help and hope it will.
> Will it be likely that your ISP block some ports or the UK side blocked some
> ports or hosts in your side?



> > I'm getting a no route to host error sporadically (about 4% of the
> > time in a 2 hour period) with connecting to a certain host in the UK.
> > I'm in the US.  When trying to track down where this is coming from, I
> > did a sniffer trace from my end and found that there are *no* ICMP
> > messages being received regarding this error.  How else could a tcp
> > socket open/send give me a "No Route to Host" message without having
> > received the ICMP telling it so?  (BTW, the host is blocking all ICMP
> > on its end.  I'm not.)

> > My configuration--Red Hat 7.2, single proc, kernel 2.4.7-10smp, x86
> > box with 512M ram.  The CPU is not all that busy and the system is not
> > loaded, there is plenty of RAM free, etc.

> > Donald E. Foss

 
 
 

1. ICMP HOST cannot build IP Header address to echo ICMP HOST

 this is the error message i get when trying to telnet anywhere but to my
domain serveror ping anything but my domain server i also get it when logged
into any other machine but my domain server even machines on the same net will
recognize dns make an attempt then puke! i assume this a problem in my
config which is preventing the returning or "echoing" of the returns off of
commands that require two way communication i have tried everything that i
know and then some!! please HELP ME !!!!!!!!!!!!
                                    thanks big time in advance


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