Server :: DNS Server Not Reachable From Different Subnet Intermittently
Aug 27, 2010
We are having two DNS servers working as master and slave in our DMZ network subnet.DMZ network consist other servers also, but only the DNS servers intermittently becomes unreachable (no ping response) from different subnets whereas the internal communication (within subnet) happens at that time.From the DNS server we are unable to ping gateway ip also when the issue arises.We tried changing the port where DNS servers connected in DMZ switch and even reformatted the OS and reconfigured DNS but nothing seems to be working.We even tried changing the IP address of the server but after few days the New IP Address also gets affected
We google around a lot tying to fix the issue but no solution has yet come up.We are not even sure whether it is server issue or a network issue.
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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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Sep 9, 2011
I have tftp-server running on Centos 5. Clients which are on the same subnet as the server are able to get and put without problems. I have a client that is across the internet that is having trouble getting files from my tftp server. A tcpdump reveals that the client is requesting the same file over and over again. In /var/log/messages, I am see the following error repeated over and over until the client finally gives up.
localhost in.tftpd[12727]: tftpd: read: No route to host
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Aug 28, 2010
I have a remote machine on which my server application runs. The remote server is linux based. What and all steps I would required do to IDENTIFY and SOLVE if The server is not reachable
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Jun 14, 2009
I would like to setup 2 linux machine each with two ethernet cards, and need to connect to two subnet e.g. 192.168.*.* and 10.0.*.* . If one linux machine out of order, the other will take over all the services(1 httpd and two named(192.168.*.1 and 10.0.0.1 as server ip). What network config is best and easy to failover to other machine?
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Aug 28, 2010
I have a remote machine on which my server application runs. The remote server is linux based. What and all steps I would required do to IDENTIFY and SOLVE for following two problems
1. The server is not reachable
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Mar 7, 2011
Was trying to understand the behavior of TCP when the server becomes unreachable . For this I am using vsftpd and the default linux ftp client to check the behavior.I was trying the following things. Was Trying to download a file from an FTP server using the FTP client as anonymous user. While the file is getting downloaded, I removed the network cable from the FTP server to understand the behavior of TCP when the server becomes unreachable.
As per the functionality of TCP/IP , when the server becomes unreachable for whatever reason , the client tries retransmitting the data till it can send the data or it timeouts. But in my above experiment using FTP , I can see that the FTP client is not trying to retransmit data at all . This I came to know using by sniffing FTP traffic at the client side. Is this expected or default FTP client available in Linux does not obey TCP/IP functionality properly ?
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Dec 8, 2009
I have two machines, one used as client and the other as server. I want to check if the port 7080 on server reachable from the client machine.How can I do that? Using telnet?
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May 3, 2011
A question that I've asked myself (and google) many times but never got to an answer.Scenario:ServerA) postfix Primary MXServerB) postfix Backup MXAccording to the rfc a source mailserver can decide where to send email e.g.send an email to backup even is primary is reachable up and running.So my questions are: 1) how do I (live I mean) replicate messages arrived on any server to the other?2) How do I synchronise sent messages, message deletion, folder creation/deletion.Imapsync goes half way towards the solution but it needs to be run manually one off and you must specify source and destination.All I wanted really is a user to be able to use either server without having to worry about primary/secondary or what so ever.
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Sep 1, 2011
The attached log file includes two crashes/reboots within the past day or so I have recently started trying to set up / manage a Linux (Ubuntu 10.04.2 LTS) server in our data center (all other servers are Windows boxes). The server periodically hangs and becomes unresponsive and I'm at a loss to find anything in any log that indicates a specific cause. Sometimes it's up for hours, sometimes days (14 days at longest). Plugging a monitor in to the machine after a hang shows nothing at all. In an effort to troubleshoot the problem we've tried disabling APIC, more out of "educated desperation" than anything else. Unfortunately we are limited in some of the troubleshooting we can do, as we have a single client website hosted on the box (the reason we set it up) so anything that involves significant downtime is a problem.
As this is our first attempt at setting up a linux box, we are using a "well equipped" desktop grade machine but not what I would call "server grade" hardware. This is a standalone box, not a VPS. We are using a hardware, not software, RAID array and have plenty of memory in the box.
Caveats / Background:
I am relatively new to Linux in general. I spend much more time writing code than managing servers. I'm comfortable with working on the box, but I'm not really a sysadmin guy. I'm comfortable with the command line but have more experience with OS X (BSD). I am unsure of all of the tools / information / Logs that may be available, though I try to be thorough in checking what I do know. I did not physically configure the hardware so I'm not sure of all of the specs but I can get any info I need to troubleshoot. I may be skipping very basic steps or missing obvious places to look for information without knowing it.
A little more detail:
Real memory: 8GB
Ubuntu 10.04.2 LTS
Hardware RAID 10
Managing sites with Webmin version 1.550
Server is in a remote data center. Hands on-troubleshooting is difficult. We have attempted two Linux setups at this point. The first was on a hardware config identical to this one, but with no actual pieces of hardware reused. That attempt was using CentOS and we were attempting to set up CPanel. We scrapped that install because of this same problem (periodic crashing / hanging). The second attempt (this one) is showing the same behavior. The only thing I can really see in common are the hardware configuration (though CentOS & Ubuntu may have more in common than I think).
The box will run fine for hours, days, or even weeks, and then just stop responding entirely. I check all of the logs I know to check (primarily messages, syslog and kern.log) but I don't see anything that seems like an error to me. I do see lines that I don't understand that may or may not be problems, such as:
Code:
rsyslogd: [origin software="rsyslogd" swVersion="4.2.0" x-pid="814" x-info="http://www.rsyslog.com"] rsyslogd was HUPed, type 'lightweight'.
Most of our syslog entries seem to be logs of webmin related cron jobs running. My gut tells me that there is possibly some component in our configuration Linux does not like or needs a driver update (maybe the raid card for example), but I'm unsure of how to do more to track down or determine what that might be. Guess and check is expensive. Another thought I've had is that one or more of the cron jobs that are running are tripping something up, but it doesn't appear to be reproducible on demand and, again, I'm at a loss on how to test that theory any further. The same cron job does not appear to be running each time the server goes down. This is a portion the log just prior to our last hang:
Code:
Aug 8 11:00:01 linhost01 CRON[10771]: (www-data) CMD ([ -x /usr/lib/cgi-bin/awstats.pl -a -f /etc/awstats/awstats.conf -a -r /var/log/apache2/access.log ] && /usr/lib/cgi-bin/awstats.pl -config=awstats -update >/dev/null)
[code].....
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Jun 8, 2010
I am trying to provide dynamic IP addresses for devices that are on a different VLAN (101). The server is currently providing 172.17.x.x/16 range for its own VLAN (417). My server is RHEL4 and DHCPD is version 3.0.1. The core switch (Cisco 3750) is configured with ip-helper on VLAN 101 interfacce. Here is my dhcpd.conf file:
authoritative;
ddns-update-style ad-hoc;
omapi-port 7911;
shared-network eth1
[code].....
However my laptop on the VLAN 101 keeps getting IP of 172.17.x.x/16 range..
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Dec 2, 2009
I am new to Ubuntu 9.10. I have installed Ubuntu and it's working fine. I would like to set fix IPAddress and Subnet.
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Feb 24, 2011
how to configure reverse zone for x.x.x.x/18 subnet ,all the example on the internet are for /24 or /16 subnets?
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Jul 8, 2011
My environment in a nutshell is like this:
- I'm a member of a Windows AD domain environment that spans many different subnets.
- My client workstation (Windows XP) is part of this domain and resides on one subnet.
- The server I'm trying to get Samba working on (SLES 10) is part of the same domain but resides on a different subnet.
- I want to access shares on the SLES 10 box from my workstation.
Here is what does work:
1. I can ping the workstation from the SLES box, both by hostname and ip.
2. I can ping the SLES box from my workstation, both by hostname and ip.
3. netstat -an shows that the SLES box is listening on ports 139 and 445.
4. I can telnet from my workstation to the SLES box on ports 139 and 445.
5. Output from smbclient -L coolserver (hostname obfuscated):
Code:
Anonymous login successful
Domain=[COOLDOMAIN] OS=[Unix] Server=[Samba 3.5.8-30.4-2516-SUSE-CODE10-x86_64] .....
Code:
Enter cooluser's password:
Domain=[COOLDOMAIN] OS=[Unix] Server=[Samba 3.5.8-30.4-2516-SUSE-CODE10-x86_64]
smb: >
So, cross-subnet communication seems to be working in a general sense and I have verified that my share is present and accessible by my chosen user id.
Here's what doesn't work (from the workstation):
1. Output from net view \coolserver:
Code:
System error 64 has occurred.
The specified network name is no longer available.
2. Output from net view \coolservercoolshare:
Code:
System error 5 has occurred.
Access is denied.
3. Same output as above if I try to connect via IP.
However, when I run any of the above commands from my workstation, I see the following in log.smbd on the SLES box:
Code:
coolworkstation (10.49.140.36) connect to service coolshare initially as user cooluser (uid=12171, gid=500) (pid 29039)
[2011/07/08 00:39:29.098422, 1] smbd/service.c:1251(close_cnum)
coolworkstation (10.49.140.36) closed connection to service coolshare
I'm not really sure how to interpret this because those are the exact same entries that get logged when I connect to the share locally, via the smbclient utility on the SLES box, which works fine... but from the Windows box I get the "Access is Denied" or "The specified network name is no longer available" errors. I also occasionally see this in log.smbd:
Code:
[2011/07/08 01:01:19.858308, 1] smbd/server.c:240(cleanup_timeout_fn)
Cleaning up brl and lock database after unclean shutdown
[2011/07/08 01:01:33.828692, 0] printing/print_cups.c:108(cups_connect)
Unable to connect to CUPS server localhost:631 - Connection refused
[2011/07/08 01:01:33.832127, 1] smbd/server.c:282(remove_child_pid)
Could not find child 29781 -- ignoring
I don't know if that is relevant. I created the Samba user via the smbpasswd utility and my smbusers file maps the system user directly to the Samba user, both of which have the same password. Here is my smb.conf:
Code:
[global]
workgroup = COOLDOMAIN
netbios name = coolserver
domain master = no
preferred master = yes
local master = yes
wins support = no .....
My workstation and the SLES box are both pointing to the same WINS server, which services the entire domain (which is also one of the DC's and one of the DNS servers). I'm really not sure what's going on. I'm guessing it probably has something to do with the subnet boundaries or the WINS configuration or something along those lines. I just don't understand because the smb daemon seems to be logging "successful" sessions from my workstation... but then the session just insta-closes.
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Oct 24, 2010
I've got a bit of a question. My network is laid out like this:
The role assignments are thus:
Firewall - sorts out the passing through to the 3 different networks, and acts as the traffic proxy.
Windows 2003 server - Does Active Directory and DNS
CentOS server - FTP and DHCP
Now, my problem is I need the CentOS server to be able to assign IP address to both networks, however, the CentOS server can *ONLY* be connected via the one interface to the firewall. It needs to assign the Windows 2003 server and the eth0 of the firewall an IP address via static DHCP, but it also needs to able to assign the clients dynamically via any address in the 10.23.1.0/24 range. I was thinking that I would be able to create static only assignments for the servers via their MAC addresses, and only have 1 dynamically assignable entry for the clients, and then get the firewall to allow ports 67 and 68 to flow freely between eth0 and eth1, but I wasn't entirely sure of the best way to do all this.
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Apr 1, 2011
I had a server that I use for Radius DNS and Trying to put DHCP on it I have My pool in it seems right. I have 2 adresses aliased one being a helper IP that the router will send the request to. When I try to start the dhcp server I get the following.
Mar 31 14:33:11 rad2 dhcpd: No subnet declaration for eth0 (76.164.173.2).
Mar 31 14:33:11 rad2 dhcpd: ** Ignoring requests on eth0. If this is not what
Mar 31 14:33:11 rad2 dhcpd: you want, please write a subnet declaration
Mar 31 14:33:11 rad2 dhcpd: in your dhcpd.conf file for the network segment
Mar 31 14:33:11 rad2 dhcpd: to which interface eth0 is attached. **
[Code]...
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Apr 4, 2010
I'm establishing a server that runs DHCP server, NAT gateway and VPN server. It have two physical interfaces, one for intranet and one for internet. The NAT gateway will give internet access for intranet. Another site will connect to this server by VPN. I need the server to assign a different subnet for that site other than the local site. Do anyone know how to config the DHCP server? Should I config the client classing, and how to do it?
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Mar 10, 2011
I have an Edubuntu server with two nics joined to the primary windows domain and I can log on with domain credentials and everything is AOK. I used LikewiseOpen 6 to join the server to the primary domain. So, on my Edubuntu server eth1 is connected to the primary domain and has a static IP. eth2 also has a static IP and is the DHCP for the thin client subnet, connected to a switch. IP forwarding is enabled.
DOMAIN - eth1 - Edubuntu Server - eth2 (SUBNET) - switch - clients
So far, so good: I can log on the thin clients with one of the local accounts specified on the Edubuntu server and with that account I can surf the net and, if I supply domain credentials, browse the primary domain. Problem I have is:
I can't work out how to log on to the primary domain with a Active Directory account directly from a thin client. If I try DOMAINuser to log on, after giving the password, the password screen refreshes and 'domainuser@11.*.21.*'s password' appears under the blank password box. The IP in that message is the IP for the subnet and not the primary domain. I feel like I'm miss-understanding some basic simple step but I just can't figure it out.
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Jul 22, 2011
I have TWO L3 + router switch (say switch1 and switch2). I created VLAN100 with VLAN ID 100 in both the switches. I created router 192.168.1.1/24 in Switch1. I created router 192.168.2.1/24 in Switch2. Switch1 is connected with 1.x/24 PCs. PCs are configured with 1.1 gateway. Switch2 is connected with 2.x/24 PCs. PCs are configured with 2.1 gateway. Both Switch1 and switch2 are connected by a trunk to carry VLAN100 data.
1)I have few PCs of 1.x connected to say Switch1 Is it possible for PC with IP 192.168.1.100(x) to ping PC with IP 192.168.2.100(y)?What are the configuration required in both switches to make them communicate ? All the device in both the subnets should ping/communicate with each other.
2)Move PC (192.168.1.100) to switch2. Move PC (192.168.2.100)to switch1.What will happen when PC(1.100) ping (2.100) and vice versa?What will happen when PC(say 1.80 in switch1) pings PC (say 1.100 in switch2) and vice versa? What will happen when PC(say 1.80 in switch1) pings PC (say 2.100 in switch1) and vice versa?
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Jul 4, 2011
I installed Redhat Enterprise linux server5. it has two LAN card and two subnet connected to these two LAN card. i can browse network from these two network easily. But i created VLAN on one network card.Now i cant browse network from these VLAN subnet.
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Apr 2, 2010
I have installed a linux server in my office to run 16 machines. Its main use will be a internal mail server but will be also running websites.
I have installed Ubuntu 9.10 server x64 and have got apache running.
I am looking for the simplest more robust solution for smtp, pop3 and imap. I have only ever used qmail before and found it a pain to configure and its getting old so I though I should probably try something new. I have not much experience with running pop3 or imap on linux so would love a suggestion on that.
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Sep 29, 2010
have to create a webhost on an running fedora server which runs multiple webpages + a coldfusion serveri have to add an coldfusion virtual host to these.what i would do:*crate a new user & group*enter vhosts.conf and copy an existing host and modify it for the new one.*create an new folder and copy the main files (phpstarter and webroot) *chown the files for the right useri think an apache graceful would be needet
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May 5, 2011
Right now i have a HP DL 180 Server with 130 Gb Hard Disk & 8 Gb ram after Raiding0+1. i want to configure Domain Controller Server for my office for 200 to 300 Users. what should the partition size must be mentioned in my 130 Gb Hard Disk, is that going to be Sufficient for ME ?
i am bit confused about /Usr /Var /Boot partitions, as i need to manage perfectly in 130 GB
if i go with 4 Gb swap and remaining for " / " is that will be fine ? should i need to specify partition sizes separately for / tmp /var / usr ..
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Apr 21, 2011
I'm running a linux cloud server with the following config
1.2ghz Processor allocation
752MB Ram
The site loads slow and clicking a link almost freezes the page for a second. Also, the page loads could be much faster. We've been running mysqltuner and have pretty much optimized all slow queries. Is there anything we can do to fine tune the server for faster and more responsive?
Httpd.conf
Timeout 20
KeepAlive Off
MaxKeepAliveRequests 100
KeepAliveTimeout 5
<IfModule prefork.c>
code....
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Jun 21, 2011
iam trying to sync file server data into backup server machine by command- rsync -avu path/of/data ipaddress-of-backup-server:/path/where/to/save after running it ask for root password and manually it is successful.but i want to make it automatic.for that i also tried cronjob and also generated authentication key but iam not successful in login automatically..anybody know how to authenticate root to login for storing data in backup server.
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Jan 25, 2011
I will be relocating to a permanent residence sometime in the next year or two. I've recently begun thinking about the best way to implement a home-based network. It occurred to me that the most elegant solution might be the use of VM technology to eliminate as much hardware and wiring as possible.My thinking is this: Install a multi-core system and configure it to run several VMs, one each for a firewall, a caching proxy server, a mail server, a web server. Additionally, I would like to run 2-4 VMs as remote (RDP)workstations, using diskless workstations to boot the VMs over powerline ethernet.The latest powerline technology (available later this year) will allow multiple devices on a residential circuit operating at near gigabit speed, just like legacy wired networks.
In theory, the above would allow me to consolidate everything but the disklessworkstations on a single server and eliminate all wired (and wireless) connections except the broadband connection to the Internet and the cabling to the nearest power outlets. It appears technically possible, but I'm not sure about the various virtual connections among VMs. In theory, each VM should be able to communicate with the other as if it was on the same network via the server data bus, but what about setting up firewall zones? Any internal I/O bandwidth bottlenecks? Any other potential "gotchas", caveats, issues? (Other than the obvious requirement of having enough CPU and RAM).Any thoughts or observations welcome, especially if they are from real world experience in a VM environment. BTW--in case you're wondering why I'm posting here, it's because I run Debian on all my workstations/servers (running VirtualBox as a VM for Windows XP on one workstation).
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Feb 16, 2010
I have got a running mail server on CentOS5.4 Final using Zimbra free edition. . Assume that domain is organization.com.local And it is running fine with users created and bugzilla running on the same machine can send mails using this server. But it can obviously send messages to the internal users. There is this option to configure it to use external mail server to send mails outside the network but my external smtp server needs an authentication.Is it possible to configure it this way to use my external server to send mails from internal domain to say gmail?
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Jan 6, 2011
i recently installed apache2 mysql php exc. to run a realtime stat site for my servers.the only thing is that the buttons/ images are not showing up.i checked that my GD was up to date and installed perl5 GD. dont know what else to check.my site with problems go to:http://24.20.177.228/stats_public
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May 24, 2010
I am working on linux server with below specifications.Linux EDT 2008 i686 i686 i386 GNU/LinuxWhile checking the status of the server using the command 'opmnctl status' and when server is down the output is not getting redirected to file.I m using the command as,opmnctl status > abc.txt.
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Jan 8, 2011
i have been trying to complete the following project1) Configure a FTP server where we can upload and download files.........2) server must run at 9 pm & stop at 9 am automatically ............although the first task was easy ,i have no idea how to accomplish the 2nd task(not to mention I'm a new user)
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