Ubuntu Servers :: Server Often Unreachable In LAN?
Jul 13, 2010
I am trying to set up a virtualized ubuntu server in a local lan.In short : The server does not always answer to ping/ssh/whatever, but sometimes does, it seems completely random and dependant on the clients, it drives me crazy, what can I do to track down the problem ?In long : I will give the exact environment further down, but first the symptoms :A very strange network behaviour : the server does not always answer to ping/ssh/whatever from another computer in the LAN. It *seem*s completely random if it does or not, however I have identified some facts :- it is able to ping any computer in the LAN, or even outside (using IP or hostname) so it's connection seems ok.
- it is able to ping itself using "ping localhost"- the hyperviser is always able to ping it, however the *first* ping always fails (ie 3/4 first round then it works fine).now for the strange/random facts :- from my linux client, I can usually ping the server for about 10 minutes after I restart networking (in the ubuntu server), then it does not answer to ping/ssh/whatever anymore (though it happened that it suddenly came back for a while)- from my colleague windows client, we can ping the ubuntu server (same as the hyperviser, 3/4 first round), even when the linux client can't anymore- from my virtualized windows client, it is equal to my linux client (does not work fine)- from another linux client, same (does not work fine)- from 2 another windows machines, it does NOT work either !Now for the environment :- Hyper-V is the hyperviser on a DELL computer (not my fault, didn't have the choice)- Ubuntu server 10.04 standard install, with the synthetic network drivers activated in the kernel and defined in Hyper-V.
- A static IP- All computers in a LAN with mostly windows servers (such as DNS, AD and exchange servers)- there is another virtualized server (windows) on the same hyper-v global virtual network, with its own IP, and this one pings perfectly fine from any client.- the hyper-V also answers to ping
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Mar 7, 2011
I have two linux servers, I tried to ping from one linux box to another and vice versa but error message is "connect: Network is unreachable" Where as If I tried from windows machine I am getting the reply from both the servers.
C:Documents and Settings>ping bnkprod
Pinging bnkprod.softtech.com [172.20.40.141] with 32 bytes of data:
Reply from 172.20.40.141: bytes=32 time=16ms TTL=64
Reply from 172.20.40.141: bytes=32 time<1ms TTL=64
Reply from 172.20.40.141: bytes=32 time<1ms TTL=64
Reply from 172.20.40.141: bytes=32 time<1ms TTL=64
Ping statistics for 172.20.40.141:
Packets: Sent = 4, Received = 4, Lost = 0 (0% loss),
Approximate round trip times in milli-seconds:
Minimum = 0ms, Maximum = 16ms, Average = 4ms
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Jan 3, 2011
I have a home server running Ubuntu Server 10.10, it is running Samba for file sharing with a mix of Windows and Linux boxes in my house. My main problem is that the server is only accessible by IP or by using hostname.local, but it is not possible to connect to it by just typing the hostname. Further more, it is not being automatically discovered and listed by Windows or Linux clients.
What's really odd is that I also have an Ubuntu Desktop 10.10 install on a separate computer, and that computer is accessible using just the hostname and is automatically being discovered and listed by other computers.
What is missing on the server? What is responsible for resolving just hostname, avahi seems to only deal with hostname.local and that is working fine. I also compared the samba config of the desktop and server Ubuntu installs but wasn't able to find any setting that would be influencing this. Is there some package I'm missing on the server?
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May 25, 2011
I use DNS on my server as a chasing DNS so its not fully configured. I seem to be having trouble with IPV6 addresses. I'm guessing this is linked to the 6to4 tunnel I have set up to my windows box, but I'm not really sure.
Code:
May 21 18:00:16 hyrule named[1148]: error (network unreachable) resolving 'D.ROOT-SERVERS.NET/AAAA/IN': 2001:dc3::35#53
May 21 18:00:16 hyrule named[1148]: error (network unreachable) resolving 'B.ROOT-SERVERS.NET/AAAA/IN': 2001:500:1::803f:235#53
May 21 18:00:17 hyrule named[1148]: error (network unreachable) resolving 'zg.akamaitech.net/AAAA/IN': 2001:503:a83e::2:30#53 .....
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Jan 16, 2011
I have the following two lines at the bottom of my /etc/fstab
Quote:
//172.16.6.15/e /tmp/e cifs _netdev,iocharset=utf8,credentials=/root/.smbcredentials,gid=0 0 0
//172.16.6.15/e/Public /var/www/index/pub cifs _netdev,iocharset=utf8,credentials=/root/.smbcredentials,gid=0 0 0
My server address is 172.16.6.1.
If the destination (which is my workstation desktop) 172.16.6.15 is offline when the server tries to boot, the entire boot procedure halts with the following message: Unable to find suitable address. mountall: mount <destination> terminated with status 2 The problem is that my server runs headlessly, and every time something silly like this happens where you'd normally expect the OS to continue regardless, I'm forced to plug a monitor in and diagnose on console
So my question: Is there any way to make it proceed with the boot normally despite the host being unreachable? I could probably chuck a mount command into crontab or /etc/rc.local or a /etc/network/if-up.d script, but isn't this the way it really should be done (/etc/fstab)? If so, then we shouldn't expect the entire boot to halt just because a network share can't be mounted, right? While on the topic of a headless ubuntu server 10.10 not booting without some kind of intervention, I have yet another issue: If the server goes down without proper shutdown (power failure, for example) the grub menu displays the kernel choices and there's no countdown timer. Instead, I have to manually press enter to continue the boot. Is there any way around this? Clearly this should not be the case for a server distribution
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Jan 15, 2010
I have a ubuntu desktop 9.10 that is used as a file server and occasionally as a desktop. My problem is after about 15 min of idle the server can not be accessed by other computers. I attempted to disable power management but Im not sure if i did that correctly. Where should i look for problems?
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Jan 28, 2010
I have a CentOS5 box here (actually running the latest release of EasyIDS). Everything was working fine for about half an hour, and now I can't access the box through a web browser on it's IP address. I can't ping the box either. If I log on to the server, I can ping other boxes on the network and external resources, but nothing seems to be able to see it. I checked to make sure HTTPD is running, and it is. The firewall is not running (or at least that's what it says when I do service --status-all).
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Jun 8, 2010
i have a problem with my internet connection in ubuntu 8.04 server edition. if i ping to: [URL]... i get: Destination Host Unreachable but when i ping to my gateway or other pc's in my network no problems occur.
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Aug 19, 2010
This is on Ubuntu 10.04 Server Edition. The ethernet cord was disconnected one day. I plugged it back in to find I can ssh to and from that machine, but I cannot update or browse the web (elinks) on it. I tried "ifconfig eth0 up" which did nothing. Why is it that only local connections work?
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Dec 27, 2010
I've been having a lot of trouble with getting wireless networking devices to work. I guess I have a lot of company, since mfrs don't seem to be very interested in supporting Linux.It seems that one common symptom is that, when I try to "Ping" using the Terminal, I get "network is unreachable".Does this mean anything specific, or is it a general output whenever the network is not carrying on two way communications? Does it mean that the wireless interface is down? Does it mean that the wireless hardware is not transmitting? Not receiving?
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Jan 3, 2011
My ubuntu installation was running fine with the Belkin F7D1101 v1 after using this install method:[URL]..But, after allowing ubuntu to autoupdate many programs (don't remember which ones), the device stopped working. I checked all of the commands in the link above. They are all still functioning. dmesg throws no errors, but it terminates with
<code>ADDRCONF (NETDEV_UP): wlan0: link is not ready</code> Are there any network files which may have been overridden from autoupdate? iwconfig wlan0 shows "Access Point: Not-Associated" What output can I show you to help me find the problem?
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Jul 28, 2011
I dont even know where to start looking on Google.Just in case this matters, for completeness.I've an inactive eth0 (wired ethernet link) with static IP.Other possibly relevant details:I'm using an old 802.11b card. Cant imagine this is relevant, because the internet is working fine as far as pinging anything outside the local network goes.
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Aug 9, 2011
I have Ubuntu machine with cifs share mounted at boot via /etc/fstab
fstab entry looks like this:
/kain/buksica /media/buksica smbfs owner,_netdev,gid=xxxx,uid=xxxxx 0 0
When my coleague shuts down his windblows machine my Ubuntu box freezes.. I cannot even open my home folder.
Is there any way kernel can detect that this share is down and silently umount it or in some other way keep stable.
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Oct 3, 2010
I have a network printer directly connected via ethernet cable to an Ubuntu netbook, but pinging the printer fails, giving "Host Unreachable". The network light on the ethernet socket is lit green, and there is nothing else cable-connected to the network - just a simple cable connection between the netbook ethernet socket and the Network printer (a HP Laserjet 4200n). Ping works fine if I plug the cable into a different machine (a Win XP box) and ping from there, so it's not a cable or IP address problem.
This sounds simple enough and should work, but I'm stumped. Clues, anyone?
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Dec 15, 2010
I'm experiencing massive latency/unreachable problems on my Linux machine. It's true for all network connections, here's an example of me trying to ping my router:
PING 192.168.0.1 (192.168.0.1) 56(84) bytes of data.
64 bytes from 192.168.0.1: icmp_req=1 ttl=64 time=15115 ms
64 bytes from 192.168.0.1: icmp_req=2 ttl=64 time=14107 ms
64 bytes from 192.168.0.1: icmp_req=3 ttl=64 time=13107 ms
64 bytes from 192.168.0.1: icmp_req=4 ttl=64 time=12107 ms
64 bytes from 192.168.0.1: icmp_req=5 ttl=64 time=11108 ms
[Code]...
I've tried now with both the maverick default kernel and 2.6.37-rc5 kernel (both 64 bit), same result. If I take the card up and down (ifup, ifdown) performance is restored for a little while, then it's back. I've tried changing cable, network card and router port but no luck.
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Jan 4, 2011
I have a strange problem with my debian lenny server. I am running ispconfig 3, squirrelmail, webmin, clamav, etc on my lenny server. I have a few domain names binded to my ip adress. Until yesterday, everything worked fine. Today, i couldn't seem to reach my mailbox, and my website appeared to be offline. But when someone checks it from outside, it works fine! Only i cant reach it. This problem only occurs with one of the six domainnames i have. The rest is reachable for me.
I checked the logs, the ipadresses, everything seems fine. I have no clue what it could be... anyone suggestions?
Figured out the problem, party... it's a problem with my XP. If i boot in Windows 7 the site is reachable. Doesn't make sense tho.
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Jul 31, 2009
I have a big pb after installing F11 : my partition containing all my photos is now unmountable. Before installing F11, it was in ext3 filesystem
During installing F11 on sda1 (first hard drive), I noticed some strange error messages like "volume doesn't exist" or something like that.
now, when I try to mount my partition of my third hard drive, i get this :
Code:
[root@vincent vincent]# mount /dev/sdc1 /home/vincent/sdc1
mount: type inconnu de systme de fichiers 'lvm2pv'
which means "mount: filesystem type unknown 'lvm2pv' "
[Code]......
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Mar 25, 2010
I have one server with 4 network interfaces:
eth0: 192.168.0.0/24 - local lan A
eth1: 200.1.2.3 - internet link - default route
eth2: 192.168.10.0/24 - local lan B eth3: 192.168.20.0/24 - local lan C
Lan A - Default routing to eth0
Lan B - Default routing to eth2
Lan c - Default routing to another server but the workstations has static routing to this server too.
Everything is working fine on Opensuse 11.1 until I upgrade this sever to Opensuse 11.2 ( Reinstall, not update at all ). After upgrade to 11.2 the routing across local lan interfaces simply not work, if you try to ping lan-to-lan you got the message: Network unreachable, even with the IP Forward enable, but the default route is working fine trough the SNAT.
I've come back to Opensuse 11.1 and everything become normal, does anyone have an problem like this? Maybe a bug? PS: I do not try to disable the AppArmor, next weekend I will try Opensuse 11.2 without the AppArmor and post here anyway.
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Jan 11, 2010
I've got router with: eth2 - local network (192.168.1.1), ppp0 - uplink (x.y.z.a)
my firewall:
Code:
# Generated by iptables-save v1.4.5 on Mon Jan 11 12:22:25 2010
*raw
:PREROUTING ACCEPT [1038480:666298388]
[code]....
somehow iptables -t nat -A PREROUTING -i eth2 -d x.y.z.a -j DNAT --to-destination 192.168.1.1 helps, but imho there should be some other solution. kernel is 2.6.31.6, architecture is x86_64.
P.S. i've also tried iptables -A POSTROUTING ! -d x.y.z.a -s 192.168.1.0/24 -j MASQUERADE that didn't help either.
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Mar 21, 2011
i'm trying to run a server for a game, that requires a few ports open (*since i connect to the internet with a router); for example one of the ports that needs to be open is "8888". But i tryed opening it thru my router localhost and it doesn't work (d-link DIR-400), so i was thinking if there's any way to open the ports of the router directly from Ubuntu; maybe console or program?for example for windows there's (Smart Port-fowarding) wich opens the ports you want without goint thru the router page.
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Aug 17, 2010
Flashed bios lastnight on 13.0 desktop.
all winblow$ are fine.
lspci shows ehthernet card
did 'netconfig' and
'route -n' shows default settings as if /etc/rc.d/rc.inetd1.conf were never set.
oh yes, i manually edited this too. mv'd and netconfig'd.
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Aug 7, 2011
I am plagued by the following error when attempting port forwarded connections to my minecraft server. Port forwarding is good and test ok on router based firewall. No iptables entries. Natty N, all updates current.
[INFO] Disconnecting CascadianNW [/184.100.247.218:57787]: Failed to verify username! [internal error java.net.NoRouteToHostException: Network is unreachable]
java.net.NoRouteToHostException: Network is unreachable
Some discussion indicate jvm network connection issues related to ipv6, but they are old posts.
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Jan 18, 2010
I want to add this route but I am getting this error message. What is the reason of this problem? I cant add this route? how can i add?
Code: [root@linux/]# route add -net 10.1.0.0 netmask 255.255.0.0 gw 10.2.0.1 eth0 SIOCADDRT: Network is unreachable
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Oct 26, 2009
I'm using a single raw socket to read UDP packets from local test network with 1024 ports. Each UDP src and dest port is unique and I need access to IP and UDP header fields. I can stream and process data (in and out) at 100 mbps in linux-rt kernel with very low jitter < 250 usec, 10 usec nominal.
I'd like to prevent kernel from issuing ICMP port unreachable errors back to the sending host, however, I don't want to create 1024 vanilla UDP sockets and bind to each one because of resource constraints. Currently, I'm using iptables to drop the outbound port unreachable messages. Does anyone know of a way (programmatic using C code) to prevent the ICMP unreachable traffic? Perhaps an IOCTL or socket option? I also tried changing /proc/sys/net/ipv4/icmp_ratelimit but that seemed to have no effect. By default the ratemask is set for dest unreachables and a variety of ratelimit values did not change any behavior that I could see.
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Sep 22, 2009
I am writing a program to read and write to devices over my serial port. My program will need to connect to up to four other machines at once. I can connect to machines successfully, it works well. However, after I connect and disconnect once, attempting to connect again will cause the FIRST serial connection will fail and all the ones after it will pass.
e.g.
Code:
fd[0]=connect("/dev/ttyS0");
fd[1]=connect("/dev/ttyS1");
fd[2]=connect("/dev/ttyS2");
fd[3]=connect("/dev/ttyS3");
code....
That works as long as it is executed only once in the program. The second time it is executed, fd[0] will die and fd[1-3] will work normally.I can't figure out why this happens, but I found a workaround by connecting to "/dev/null" before any real serial ports.What should I do?
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Jan 13, 2010
I have an HP BL460c G5 with 5.3 installed fresh
it can ping its own IP address just fine
its a bit slow but constant pinging the switch its connected to
and i get alot of Destination host unreachables(a few do get through) when pinging the gateway
port on the switch is hardcoded to GB/full. and the server itself reads that its connecting at GB/full.
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Jul 30, 2010
I have 5 1955 blades in an enclosure for an custom application cluster.All were running Centos 4.4 no problem.We wanted to start upgrading them cleanly to 5.5 so two of them got fresh installs of 5.5.The installs went well enough, no glaring errors.However they can only ping each other! The network settings are fine, no firewall or selinux. I'd run the info script but I can neither download it to them nor paste it in via kvm.Standard static entries, virtually identical to their 4.4 brethren. They ping each other so network drivers are fine, no built in switch configuration changes. It has to be some kind of network configuration issue that i'm just not seeing.
Edit* When i try and ping anything else, including the other blades, I get Destination Host Unreachable.
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May 10, 2010
i found this video, and i really want to do the same. *newbie needs to learn [URL]...my question is, what need to be installed and how?
is there any specific configuration to make it works?
and will it work if i want to connect from Ubuntu to Fedora ?
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Apr 1, 2011
I'm curious if anybody can shed some light for me in this department. We're in a large environment with a Windows DHCP Server. We have been tinkering with LTSP on Edubuntu as thin and fat clients. It works great, but right now we just have 1 server handling the lab, which works fine unless we want to expand, which may be very possible.
These are the instructions I received:
Login to your windows server and load the DHCP configuration screen
Create a DHCP reservation for the MAC address you obtained
Add the configuration options below to enable the machine to boot from the LTSP server
017 Root Path: /opt/ltsp/i386
066 Boot Server Host Name: <ip address>
067 Bootfile Name: ltsp/arch/pxelinux.0 # Specify CPU architecture in place of 'arch', for instance 'i386'
From: [url]
I'm curious, what if I want to have multiple Ubuntu servers on the network that I want to have bootable? For example, let's say I have 3 labs, and 3 servers. Server A to Lab A, Server B to Lab B, and Server C to Lab C. I want all C's computers to boot to C, and B to B, A to A, etc.
1 - How would I add multiple entries on the Windows DHCP Server to allow all 3 (A B C) servers to boot?
2 - How would I be able to isolate the clients so ONLY Lab A clients boot to Server A, etc?
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Jan 29, 2011
I'm using debian lenny.When I boot with kernel 2.6.36, ping always respond with Network is Unreachable. But when I boot with kernel 2.6.26 it works. I can't even ping the dafault router of 2.6.26 kernel when I am at 2.6.36. Also, system/administration/network does not show any connections while it shows something at the other kernel.
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