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12-14-2001, 11:45 AM
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#1
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LQ Newbie
Registered: Dec 2001
Location: DC
Distribution: RH 7.2
Posts: 13
Rep:
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think I'm getting blocked at the switch
greetings.
I'm running rh 7.1, I've fallen, and I can't get up. For days, now, I've been troubleshooting tcp/ip connection problems and I'm out of ideas. I know my NIC is configured properly because I can ping localhost, I can ping my interface AND when I network the Linux box with my laptop, everybody is happy! HOWEVER, when I plug into a LAN, I can't ping out and noone can ping in.
When I connect to the LAN, I'm plugged into a switch. I think the problem is there. Can someone suggest a troubleshooting procedure? Thanks very much.
John
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12-14-2001, 11:54 AM
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#2
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Senior Member
Registered: May 2001
Location: Left Coast - Canada
Distribution: s l a c k w a r e
Posts: 2,731
Rep:
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Do you mean you can't ping outside of your LAN or can't ping anything on your LAN?
Is your LAN tcp/ip?
Are you using the same cable that you connect to your notebook to connect to a hub/switch? If you're deadheading to another machine you're probably using a crossover cable which won' be much help in a hub unless you connect to an uplink port (scores low points for style though).
Are you on the same subnet that your LAN is operating on?
Is there a DHCP server on the LAN?
Is there a proxy/firewall involved here?
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12-14-2001, 12:09 PM
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#3
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LQ Newbie
Registered: Dec 2001
Location: DC
Distribution: RH 7.2
Posts: 13
Original Poster
Rep:
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thanks, macleodnine.
answers to your questions:
Do you mean you can't ping outside of your LAN or can't ping anything on your LAN?
I can't ping anything on my LAN.
Is your LAN tcp/ip?
Yes.
Are you using the same cable that you connect to your notebook to connect to a hub/switch? If you're deadheading to another machine you're probably using a crossover cable which won' be much help in a hub unless you connect to an uplink port (scores low points for style though).
I used a hub to network with my laptop--I've tried/tested lots of cables.
Are you on the same subnet that your LAN is operating on?
Yes, however, there is one small detail that has been stuck in my gullet:
There rest of the LAN uses netmask: 255.255.252.0 while I am using 255.255.255.0. I'm using the latter because when I set up networking with netconfig and enter the mask as 255.255.252.0, it improperly configures the gateway and network. It addresses the network as 144.171.76.0 rather than what it is: 144.171.77.0. Then if I use ifconfig to change the network back, it won't accept the netmask 255.255.252.0!
The network admins here said it should work with 255.255.255.0
Is there a DHCP server on the LAN?
No.
Is there a proxy/firewall involved here?
I don't know the answer to this. I don't believe there is either between me and the LAN. The WAN is another story but I'll cross that bridge.... Can you help me with an intelligent way to ask the network guys about proxy/firewall?
Thanks a million
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12-14-2001, 12:20 PM
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#4
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Senior Member
Registered: May 2001
Location: Left Coast - Canada
Distribution: s l a c k w a r e
Posts: 2,731
Rep:
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Are you using the same hardware (10Base-T, 100Base-T)?
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12-14-2001, 01:10 PM
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#5
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LQ Newbie
Registered: Dec 2001
Location: DC
Distribution: RH 7.2
Posts: 13
Original Poster
Rep:
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The switch is 100-full duplex. I have two network interfaces on the Linux server, both are 10/100 (one is integrated and one is a card). I have disabled the card. By default, the interface is set to autonegotiate. But I have also tried using mii-diag to advertise and then to force the interface to 100-full, but that didn't make a difference. Even if I had this setting messed up--would that prevent me from pinging out? One other thing, when I run tcpdump, I can see lots of activity (I assume this is broadcast info--right?).
thanks again.
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12-16-2001, 12:49 AM
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#6
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Member
Registered: Jun 2001
Location: 28N,82W
Distribution: XP,Ubuntu 9
Posts: 473
Rep:
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John,
Connecting to a laptop is different from connecting to a LAN. You said you are using a hub to connect to your laptop. Hub is not a DHCP server, and almost certainly you are using a static ip address to connect to your laptop.
(I am curious to know if you are able to only ping your laptop, or are able to share files across, may be using samba?)
You must configure your eth0 (or 1) to use DHCP when u connect to LAN.
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12-16-2001, 01:47 PM
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#7
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LQ Guru
Registered: Jun 2001
Location: South Alabama
Distribution: Fedora / RedHat / SuSE
Posts: 7,163
Rep:
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connect cable to lan, make sure light comes on, this will not mean it works but if it don't come on it means it don't work.
then run this
dhcpcd eth0
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12-16-2001, 03:12 PM
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#8
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LQ Newbie
Registered: Dec 2001
Location: DC
Distribution: RH 7.2
Posts: 13
Original Poster
Rep:
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Thanks concoran and David for your posts.
The LAN isn't using DHCP. I'm connecting a web server to a tcp/ip server network. My server has a static IP address. I experimented with the laptop just to make sure I have the ethernet interface configured correctly. I am not using Samba.
I need to troubleshoot my segment somehow. Suggestions? If I can successfully connect to other boxes on the network through a hub but not a switch--what does that point to??
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12-17-2001, 06:01 AM
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#9
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LQ Guru
Registered: Jun 2001
Location: South Alabama
Distribution: Fedora / RedHat / SuSE
Posts: 7,163
Rep:
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if it's not dhcp then set it up with a static ip
you can use ifconfig
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12-17-2001, 09:43 AM
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#10
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LQ Newbie
Registered: Dec 2001
Location: DC
Distribution: RH 7.2
Posts: 13
Original Poster
Rep:
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David--
I'm a bit past that point. Eth1 is set up and running with a static IP address. I can ping lo, I can ping eth1, I can monitor broadcast traffic with tcpdump, I just cannot ping the subnet and no other machines on the subnet can ping me.
jdh
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12-17-2001, 10:52 AM
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#11
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LQ Guru
Registered: Jun 2001
Location: South Alabama
Distribution: Fedora / RedHat / SuSE
Posts: 7,163
Rep:
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looking back at the other posts it sounds like the switch.
One thing if your default route and ip are on the same network and you can ping the default route and see lights flashing then maybe it is firewalled from your location and is not returning pings.
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12-17-2001, 11:02 AM
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#12
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LQ Newbie
Registered: Dec 2001
Location: DC
Distribution: RH 7.2
Posts: 13
Original Poster
Rep:
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David--when you say the default route, are you talking about the gateway? I cannot ping the gateway. But it is definitely acting like a firewall issue. So you suggest that I look into the network's firewall config--not my server's firewall config, right?
thanks,
John
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12-17-2001, 12:18 PM
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#13
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LQ Guru
Registered: Jun 2001
Location: South Alabama
Distribution: Fedora / RedHat / SuSE
Posts: 7,163
Rep:
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you could hookup another machine like a windows one and see if it's in your linux box or not, if the windows machine pings out from the same switch then that would confirm it. Also you could try hooking the linux box and laptop together with a hub or crossover cable and try pinging each other.
A lot of machines will not return pings, my home machine for one will not.
however I can ping a machine from home and can receive the echo back from the machine. It really depends on the firewall configuration.
what other connections have you tried besides ping? Is there an http server you can try? most networks have port 80 open.
To resolve this problem please post the following
output of ifconfig -a
output of route -n
output of ping to gateway
are you using iptables or ipchains?
have you tried flushing the firewall rules?
Last edited by DavidPhillips; 12-17-2001 at 12:21 PM.
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12-17-2001, 12:51 PM
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#14
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LQ Newbie
Registered: Dec 2001
Location: DC
Distribution: RH 7.2
Posts: 13
Original Poster
Rep:
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I did try connecting the Linux box with a laptop through a hub and it worked fine. They saw each other immediately.
I haven't tried anything but 'ping.' I believe there are a couple http servers on the subnet. Can I query them from a terminal with something other than ping? Would I just use Lynx?
ifconfig eth1 returns:
inet addr: 144.171.77.38 Bcast: 144.171.77.255 Mask: 255.255.255.0
UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1
RX Packets: 5523 errors:0 dropped:0 overruns:0 frame:0
TX Packets: 368 errors:0 dropped:0 overruns:20 carrier:0
collisions:15 txqueuelen:100 interrupt:15 Base address:0x2040
route returns:
dest gw genmask flags metric ref use if
144.171.77.0 * 255.255.255.0 U 0 0 0 eth1
127.0.0.0 * 255.0.0.0 U 0 0 0 lo
0.0.0.0 144.171.77.252 0.0.0.0 UG 0 0 0 eth1
pinging the gateway returns:
Destination Host Unreachable
I haven't done anything with iptables or ipchains.
I have not tried flushing the firewall rules.
thanks again for your help.
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12-17-2001, 02:18 PM
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#15
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LQ Guru
Registered: Jun 2001
Location: South Alabama
Distribution: Fedora / RedHat / SuSE
Posts: 7,163
Rep:
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ok it looks like all is ok,
when you get Destination Host Unreachable it is a good sign that the host is just not replying, not a problem on your end.
However you should have more info from ping that is important
[david@Microdot david]$ ping 1.0.0.1
PING 1.0.0.1 (1.0.0.1) from 192.168.0.7 : 56(84) bytes of data.
From 65.208.9.153: Destination Host Unreachable
Note the From ip which is a machine talking to mine. This means it is working.
try this
ping -b 144.171.77.255
Last edited by DavidPhillips; 12-17-2001 at 02:21 PM.
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