windows - DNS requests failing from computers that can ping DNS server

I have a situation where computers in some of our remote offices from time to time lose the ability to use our DNS server (in head office) to resolve hostnames. The offices are connected via VPN using Cisco ASA 5505 (VPNclient config rather than Site to Site) connecting back to an ASA 5510 at head office.

Ping to the IP address of the DNS server works. But nslookup will get a "no response from server" message. Computers in other locations can use DNS fine.

This is an intermittent problem. One day/hour it works, another it doesn't. Other offices connected in the same way work when another doesn't.

No config changes have been made on routers around the time we see the problem.

The DNS server that drops out for the clients is on our private address space in the 172.16.0.0/12 network. The ASA 5505s and the clients behind them are each in a 10.6.x.0/24 private address space.

Each ASA 5505 has its DHCP server configured to assign addresses and DNS config to clients behind them -these are generally Windows XP clients, with a growing number of Windows 7. The primary DNS is our one in the 172.16.0.0/12 space, the secondary is 8.8.8.8 to allow access to the internet in case the VPN tunnel drops for any reason.

Some users have reported that the problem goes away after doing a repair connection in Windows XP. I think this could be caused by the DNS cache being flushed as part of this - the Windows DNS cache makes the intermittent problem look less so because it caches failed lookups as well as successful ones. However, it is possible some other aspect of Windows is involved. Windows 7 clients have also had the same problem.

Any pointers on deeper troubleshooting, or anyone else found this?

Comments

linux - iDRAC6 Virtual Media native library cannot be loaded

When attempting to mount Virtual Media on a iDRAC6 IP KVM session I get the following error: I'm using Ubuntu 9.04 and: $ javaws -version Java(TM) Web Start 1.6.0_16 $ uname -a Linux aud22419-linux 2.6.28-15-generic #51-Ubuntu SMP Mon Aug 31 13:39:06 UTC 2009 x86_64 GNU/Linux $ firefox -version Mozilla Firefox 3.0.14, Copyright (c) 1998 - 2009 mozilla.org On Windows + IE it (unsurprisingly) works. I've just gotten off the phone with the Dell tech support and I was told it is known to work on Linux + Firefox, albeit Ubuntu is not supported (by Dell, that is). Has anyone out there managed to mount virtual media in the same scenario?

ubuntu - Monitoring CPU, Mem, disk, on a single server

I've been looking for a simple starter solution for monitoring my [currently] single server hosted solution. Other than Nagios and similar, are there other good (simple) solutions people are using? Answer Everything depends on what you want. For example Munin is very simple, you can install and configure it in less then 10 minutes (on one server), it can sends alarms, make graphs from monitoring cpu, mem. apache connections, eaccellerator, disk io and many many more (it has many plugins). But if you are planning in future get some more machines, munin may not be enough. For example in munin you cant monitor state of individual processes, can't monitor changes in files (for security purpose). So if you wanna only see what is the utilization of basics parameters on your server and don't plan to buy some more servers Munin is what you are looking for, but if you wanna be alarmed when some of your service is down, take more control on what is happeninig on...

hp proliant - Smart Array P822 with HBA Mode?

We get an HP DL360 G8 with an Smart Array P822 controller. On that controller will come a HP StorageWorks D2700 . Does anybody know, that it is possible to run the Smart Array P822 in HBA mode? I found only information about the P410i, who can run HBA. If this is not supported, what you think about the LSI 9207-8e controller? Will this fit good in that setup? The Hardware we get is used but all original from HP. The StorageWorks has 25 x 900 GB SAS 10K disks. Because the disks are not new I would like to use only 22 for raid6, and the rest for spare (I need to see if the disk count is optimal or not for zfs). It would be nice if I'm not stick to SAS in future. As OS I would like to install debian stretch with zfs 0.71 as file system and software raid. I have see that hp has an page for debian to. I would like to use hba mode because it is recommend, that zfs know at most as possible about the disk, and I'm independent from the raid controller. For us zfs have many benefits, ...

Blog

Search This Blog