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santanu
*nix forums beginner
Joined: 22 Feb 2005
Posts: 9
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 Posted: Mon Feb 14, 2005 6:52 am Post subject:
Re: Can't get internet working in Linux
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Moe Trin wrote:
| Quote: | Two most likely problems:
1. Make sure Explicit Congestion Notification is off. Some routers
drop all
packets with header bits set that they don't understand. The syntax
is
echo 0 > /proc/sys/net/ipv4/tcp_ecn
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I found that /proc/sys/net/ipv4/tcp_ecn was
already set to 0. So, that does not seem to
be the problem.
| Quote: | 2. _IF_ you are on a PPPOE type network, try setting the MTU back
slightly.
See RFC1435 and 2923. As root, this can be done with the
/sbin/ifconfig
command.
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Tried setting MTU down to 1490, but the
problem still persists.
Anyway, on the bright side I :
o successfully removed that routing
line for the 169.254.0.0 'ghost'
network.
o Chose another host 192.168.10.3 as
as a gateway (it is in fact a proxy
server for our network, and its gateway
is the 192.168.10.9) and could get
internet by directing my browser to
this proxy. Of course, I still can't
ping www.google.com.
Instead I get:
====
[santanu@techno santanu]$ ping www.google.com
PING www.google.akadns.net (64.233.187.104) 56(84) bytes of data.
| Quote: | From 192.168.10.3: icmp_seq=0 Redirect Host(New nexthop: 192.168.10.9)
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--- www.google.akadns.net ping statistics ---
6 packets transmitted, 0 received, 100% packet loss, time 5009ms
====
Though this solves my problem temporarily,
I would still like to know what is actually
preventing it from using the 192.168.10.9
gateway, especially since the 192.168.10.3
is a Red Hat 7.3. (However, I could not look
at its configuration since the person who
is in charge of it is not present today.
Will try again on Wednesday.)
Anything else I should try in the meantime?
Regards,
Santanu |
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Moe Trin
*nix forums Guru
Joined: 20 Feb 2005
Posts: 972
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| Posted: Mon Feb 14, 2005 7:44 pm Post subject:
Re: Can't get internet working in Linux
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In article <1108367532.461766.227900@l41g2000cwc.googlegroups.com>,
santanu wrote:
| Quote: | I found that /proc/sys/net/ipv4/tcp_ecn was
already set to 0. So, that does not seem to
be the problem.
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OK
| Quote: | Tried setting MTU down to 1490, but the
problem still persists.
|
OK
| Quote: | Anyway, on the bright side I :
o successfully removed that routing
line for the 169.254.0.0 'ghost'
network.
|
As noted, it's not critical.
| Quote: | o Chose another host 192.168.10.3 as
as a gateway (it is in fact a proxy
server for our network, and its gateway
is the 192.168.10.9) and could get
internet by directing my browser to
this proxy.
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Concept problem. The "gateway" is that host that you send packets to that
will forward them to the "other" network (in this case, the world). This is
normally a host with two (or more) network interfaces - one on your net, and
another on a different net that leads to the desired place. Here, you are not
using the gateway, but a proxy service for one application.
| Quote: | Of course, I still can't
ping www.google.com.
Instead I get:
====
[santanu@techno santanu]$ ping www.google.com
PING www.google.akadns.net (64.233.187.104) 56(84) bytes of data.
From 192.168.10.3: icmp_seq=0 Redirect Host(New nexthop: 192.168.10.9)
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Exactly - 192.168.10.3 is complaining that you are sending the packets to
the wrong place, and you should send them to 192.168.10.9. See the
"Linux Network Administrator's Guide", which may be on your system, but
can also be found at any LDP mirror or http://tldp.org/guides.html
| Quote: | Though this solves my problem temporarily,
I would still like to know what is actually
preventing it from using the 192.168.10.9
gateway, especially since the 192.168.10.3
is a Red Hat 7.3.
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192.168.10.3 is just a proxy server for web pages. The World Wide Web is
only one of several thousand network services available, such as DNS, ftp,
finger, telnet, SSH, and on and on (see /etc/services). Do you use a web
browser as a word processor or spread sheet application?
In your previous post, you showed
| Quote: | [root@techno santanu]# traceroute 202.9.145.6
traceroute to 202.9.145.6 (202.9.145.6), 30 hops max, 38 byte packets
1 192.168.10.9 (192.168.10.9) 0.842 ms 0.903 ms 0.793 ms
2 static61.11.71-1.dsl-cal.eth.net (61.11.71.1) 37.180 ms 37.484 ms
117.395 ms
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and that says the routing is correct. It was sending packets on to the
internet (as we see because names are being resolved. The fact that the
192.168.10.3 system can get out (can it also ping?) and your system can
not says there is something different in the configuration. I would
suggest using tcpdump to see what the packets are saying when you try
to _connect_ (not ping) to some web server like google or yahoo.
Old guy |
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thisissantanu@gmail.com
*nix forums beginner
Joined: 15 Feb 2005
Posts: 7
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| Posted: Tue Feb 15, 2005 10:39 am Post subject:
Re: Can't get internet working in Linux
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Moe Trin wrote:
| Quote: | o Chose another host 192.168.10.3 as
as a gateway (it is in fact a proxy
server for our network, and its gateway
is the 192.168.10.9) and could get
internet by directing my browser to
this proxy.
Concept problem. The "gateway" is that host that you send packets to
that
will forward them to the "other" network (in this case, the world).
..... |
Yes, I do understand that. I meant to say that
previously I was not getting Net, and now I at
least I can reply to this thread without leaving
the Linux machine.
| Quote: | [root@techno santanu]# traceroute 202.9.145.6
traceroute to 202.9.145.6 (202.9.145.6), 30 hops max, 38 byte
packets
1 192.168.10.9 (192.168.10.9) 0.842 ms 0.903 ms 0.793 ms
2 static61.11.71-1.dsl-cal.eth.net (61.11.71.1) 37.180 ms 37.484
ms
117.395 ms
and that says the routing is correct. It was sending packets on to
the
internet (as we see because names are being resolved. The fact that
the
192.168.10.3 system can get out (can it also ping?) and your system
can
not says there is something different in the configuration.
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The guy in charge of 192.168.10.3 says that even that
machine has the same problem as this one! The SQUID
server is working fine, and the browsers on that machine
too use Squid to access the Net.
Another thing. I was wrong when I said that Windows was
not having this problem. Actually, on Monday when I
tried to ping google from windows, it failed, even
tracert showed similar result like traceroute under
Linux. However, telnetting to port 80 of websites
succeeded. This made me feel that 192.168.10.9 was
allowing only WWW access. But if that's the case,
then why, when browsing from Windows, I dont have to
point the browser to any proxy, while from Linux, I
have to (to 192.168.10.3)??
| Quote: | I would
suggest using tcpdump to see what the packets are saying when you try
to _connect_ (not ping) to some web server like google or yahoo.
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Ahh.. thanks for the suggestion. I forgot about it.
Will try on Wednesday. Hoping to find something interesting
(if I understand the tcpdump output, that is (yes, I know,
NAG and man pages are my friend)) 
(Or maybe ethereal)
Regards,
Santanu |
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