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Slow upload to Server 2008 DC, Downloads work as expected

- by Anthony

I have a Windows Server 2008 Domain Controller that I run as a do-it-all server. It has a GbE connection to the network and to every machine on the network. Downloads from the server file shares work as expected, between 70MB/s and 80MB/s to all the machines. However, when I try to copy files back up to the server, speeds fall to 7MB/s-10MB/s. I've disabled flow control and large send offload properties on all the NICs. I had this problem before and managed to fix it through some properties changes, but like an idiot, I never documented my fix and have since moved to a new server. Any ideas what I need to do to get the speeds to be more symmetric? EDIT: Remote differential compression is also disabled.

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How to monitor network interface card utilization ?

- by kashyapa

I want to check the utilization of the network interface card while running a communication-intensive benchmark . Can anybody tell me which unix/linux command I can use to monitor the network traffic ?

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VirtualBox no network access

- by Frantumn

I'm on a work machine, setting up a virtual ubuntu image using virtual box. After I installed the image, I can't seem to connect to the internet. If I look at network and sharing center on my host OS (W7) I see that the VirtualBox Host-Only Network reads as "no network access" How can I set it up so that it uses the same network as the host OS. UPDATE! Okay, is there a way I can tell virtual box host-only network to use a proxy script?

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Unable to ssh to a Linux VM after a day

- by jogabonito

I have a machine running 4 VMs on it. There is one Fedora VM which is causing me some trouble. The IPs of the VMs are something like 10.100.100.* I have a Windows PC which is in the same network. It has an IP 10.100.25.77. When I reboot the Fedora VM, I am able to ping it from my Windows PC as well as use putty to ssh to it. The next day, I cant ping it or ssh from my Windows PC. However I can ping and ssh to the other VMs on the machine. If I ssh to one of the other VMs, I can ping and ssh to the Fedora VM. Next if I restart it, things get back to normal and I can access it without any issues. The IP of the VM doesn't change after rebooting and it is statically assigned I would like to know what is causing this and how to get it fixed. As a last resort, I am thinking of running a cron job to restart the VM every night, it is not a critical server, but will be generally used occasionally in the day time.

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Connecting via ShrewSoft VPN client means no LAN internet access (Windows 7 64 bit) - any advice please?

- by iwishiknewmoreaboutnetworking

I have a Windows 7 64 bit desktop machine which is connected to a LAN. I recently installed ShrewSoft VPN client v 2.1.7 on my machine so that I can connect to a license server hosted by my customer. They are running a Cisco VPN server and I originally tried (unsuccessfully!) to use the Cisco VPN client for Windows 64 bit but the default gateway wasn't being configured correctly after loading in my pcf file. Using ShrewSoft I am able to import the same pcf file, and successfully connect to the machine I need to using the VPN client software. The client machine I need to connect to has IP address 1.52.90.33. The problem is that when I am connected to the customer network using the VPN client application (and after a few minutes) I lose my LAN internet connection. I can only presume that this is because, by default the ShrewSoft VPN client application automatically tunnels all traffic through the VPN connection. I know there is an option to switch off the "Tunnel All" option on the Policy tab of the application and enter a Remote Network Resource (to "Include" or "Exclude") as "Address" and "Netmask" IP addresses however I am not sure what I need to enter here. Here is my ipconfig output before connecting to the VPN (with suffixes blanked out): Windows IP Configuration Ethernet adapter Local Area Connection: Connection-specific DNS Suffix . : ***.*** Link-local IPv6 Address . . . . . : fe80::8de3:9dbe:393a:33ba%11 IPv4 Address. . . . . . . . . . . : 150.237.13.17 Subnet Mask . . . . . . . . . . . : 255.255.255.0 Default Gateway . . . . . . . . . : 150.237.13.1 Tunnel adapter 6TO4 Adapter: Connection-specific DNS Suffix . : ***.*** IPv6 Address. . . . . . . . . . . : 2002:96ed:d11::96ed:d11 Default Gateway . . . . . . . . . : 2002:c058:6301::c058:6301 Tunnel adapter Local Area Connection* 9: Connection-specific DNS Suffix . : IPv6 Address. . . . . . . . . . . : 2001:0:4137:9e76:2cf9:38c4:6912:f2ee Link-local IPv6 Address . . . . . : fe80::2cf9:38c4:6912:f2ee%12 Default Gateway . . . . . . . . . : Tunnel adapter isatap.***.***: Media State . . . . . . . . . . . : Media disconnected Connection-specific DNS Suffix . : ***.*** Here is my route print output before connecting to the VPN: =========================================================================== Interface List 11...20 cf 30 9d ec 2a ......Realtek RTL8168D/8111D Family PCI-E Gigabit Ethern et NIC (NDIS 6.20) 1...........................Software Loopback Interface 1 14...00 00 00 00 00 00 00 e0 Microsoft 6to4 Adapter 12...00 00 00 00 00 00 00 e0 Teredo Tunneling Pseudo-Interface 13...00 00 00 00 00 00 00 e0 Microsoft ISATAP Adapter #2 =========================================================================== IPv4 Route Table =========================================================================== Active Routes: Network Destination Netmask Gateway Interface Metric 0.0.0.0 0.0.0.0 150.237.13.1 150.237.13.17 2 127.0.0.0 255.0.0.0 On-link 127.0.0.1 306 127.0.0.1 255.255.255.255 On-link 127.0.0.1 306 127.255.255.255 255.255.255.255 On-link 127.0.0.1 306 150.237.13.0 255.255.255.0 On-link 150.237.13.17 257 150.237.13.17 255.255.255.255 On-link 150.237.13.17 257 150.237.13.255 255.255.255.255 On-link 150.237.13.17 257 224.0.0.0 240.0.0.0 On-link 127.0.0.1 306 224.0.0.0 240.0.0.0 On-link 150.237.13.17 257 255.255.255.255 255.255.255.255 On-link 12

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What software is available to keep track of hundreds of servers?

- by djangofan

What good software is available (free or not free) to help me keep track of information relating to hundreds of servers, their relationships to each other (parent/child, category, type), and information on connecting to them, as well as possibly showing a picture or grid of some kind that allows me to report these relationships and key information to my supervisor. I am trying to avoid the "spreadsheet solution" or "visio solution" because I want to share this information and make changes with other persons in my server team. In other words, the solution I am looking for is a cross between a spreadsheet solution and a visio solution, providing both graphing and configuration information WITHOUT monitoring, and in a consistent format.

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How to use aliases for remote hosts when accessing locally

- by alexloh

I would like to use an alias for a remote host. For example, when instead of "ping giraffe.foo.bar.com" I want to do "ping giraffe", but only when I do it from my own machine. I am able to do this for raw IP addresses by adding an entry in /etc/hosts (ie "123.456.1.0 giraffe"), but it does not seem to work for host names.

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Why is my ethernet interface in promiscuous mode

- by nhed

I read that seeing a flag of M in netstat -i is the way to tell which of your interfaces is in promiscuous mode I run it and I see that eth1 is in promiscuous mode $ netstat -i Kernel Interface table Iface MTU Met RX-OK RX-ERR RX-DRP RX-OVR TX-OK TX-ERR TX-DRP TX-OVR Flg eth1 1500 0 1770161198 0 0 0 57446481 0 0 0 BMRU lo 16436 0 97501566 0 0 0 97501566 0 0 0 LRU This seems to be the case on all the machines I checked (All Centos6.0, both virtual and physical), any idea why ethernet devices would be in such a mode unless someone was running any pcap based app (sudo lsof | grep pcap shows nothing)? I did not see any mention of promiscuous in any of the config files (sudo grep -r promis /etc) Any ideas what puts the interface into that mode and why? p.s. most of the posts I see seem to be security related, this is not that

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VPN into multiple LAN Subnets

- by Rain

I need to figure out a way to allow access to two LAN subnets on a SonicWall NSA 220 through the built-in SonicWall GlobalVPN server. I've Googled and tried everything I can think of, but nothing has worked. The SonicWall NSA management web interface is also very unorganized; I'm probably missing something simple/obvious. There are two networks, called Network A and Network B for simplicity, with two different subnets. A SonicWall NSA 220 is the router/firewall/DHCP Server for Network A, which is plugged into the X2 port. Some other router is the router/firewall/DHCP server for Network B. Both of these networks need to be managed through a VPN connection. I setup the X3 interface on the SonicWall to have a static IP in the Network B subnet and plugged it in. Network A and Network B should not be able to access each other, which appears the be the default configuration. I then configured and enabled VPN. The SonicWall currently has the X1 interface setup with a subnet of 192.168.1.0/24 with a DHCP Server enabled, although it is not plugged in. When I VPN into the SonicWall, I get an IP address supplied by the DHCP Server on the X1 interface and I can access Network A remotely although I do not have access to Network B. How can I allow access to both Network A and Network B to VPN clients although keep devices on Network B from accessing Network A and vice-versa. Is there some way to create a VPN-only subnet (something like 10.100.0.0/24) on the SonicWall that can access Network A and Network B without changing the current network configuration or allowing devices on both netorks "see" each other? How would I go about setting this up? Diagram of the network: (Hopefully this kind of helps) WAN1 WAN2 | | [ SonicWall NSA 220 ]-(X3)-----------------[ Router 2 ] | | (X2) 192.168.2.0/24 10.1.1.0/24 Any help would be greatly appriciated!

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Setting up network sharing among four computers

- by Sanket Pethe

How do I set up network sharing with four computers running Windows 7? I have one dlink 8 port switch and a cablenet. What do I need to do to set this up?

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Setting up a DNS port redirect?

- by Svetlana

I have a domain using CloudFlare's DNS, I want to make it redirect to my server's IP (dynamic IP, port 21 blocked by ISP) which at the moment uses a No-IP DNS. The current setup is that I have a subdomain as a CNAME targetting the No-IP domain, but that only works for things like the Minecraft server (which looks for a set port that isn't blocked by my ISP), and I'd like a solution that lets me redirect port 21 from the CloudFlare domain to port 2121 on the No-IP domain, or something else that points to my dynamic IP, where an FTP server is already set up and running. I've had SRV records mentioned to me but without any further help, and it only made me more confused. Thanks in advance for the help.

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Connecting office to data center via Metro-ethernet

- by Eric

I am installing a metro ethernet link from my office to my data center. The office will have a cisco 3750 with several vlans. The data center end will have a more complicated set up. The metro e from the office will connect to a 2960, which will have two other 2960s with a few vlans and a 2811 router connected to it for connectivity to our other environments and the internet. I am looking at implementing this by connecting the office 3750 and the data center 2960 with a dot1q trunk and doing all routing at the 2811. I will configure subinterfaces for gateways for each of the vlans on the 2811. I work for a small company and don't have much of a budget for an ideal architecture. I can post a simple diagram if needed for clarification. Is there anything I am missing here? I feel like I am forgetting something very basic and want to make sure I eliminate any boneheaded mistakes.

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Flow of packets in network

- by user58859

I can't visualize in my mind the network traffic flow. eg. If there are 15 pc's in a LAN When packet goes from router to local LAN, do it passes all the computers? Does it go to the ethernet card of every computer and those computers accept the packet based on their physical address? To which pc the packet will go first? To the nearest to the router? What happens if that first pc captures that packet(though it is not for it)? What happens when a pc broadcast a message? Do it have to generate 14 packets for all the pc's or only one packet reach to all pc's? If it is one packet and captured by first pc, how other pc's can get that? I can't imagine how this traffic is exactly flows? May be my analogy is completely wrong. Can anybody explain me this?

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Hiding mapped drives for all users but letting programs access them

- by AgainstClint

What I'm looking for (and not sure if it's possible) is that we have 16 mapped network drives that are mapped when any user logs on, what I would like is to cut this down to just one visible drive yet leaving the other ones still usable to certain programs. I would just un-map them, however one of our constantly used programs writes to almost all of the drive letters so they need to be mapped for just that program, however they do not need to be visible to the user. Is this possible?

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Why are there so few Wireless N Dual Band adapter PCI cards, only USB adapters instead?

- by daiphoenix

There has been several Wireless N Dual Band routers/APs out in the market for quite some time now, and there are several Wireless N Dual Band USB adapters out there. But as for PCI/PCI-X card adapters, there seems to be only one (the Linksys WMP600N). Why is that? I find it very strange. Is it because the USB adapters are easier to install, and can be used on multiple computers? But if so, why isn't it the same case with single band (2.4 Ghz) wireless N adapters? Because for these ones there as many PCI card adapters as there are USB adapters. Also, can the USB adapters, despite the lack of external antenna, offer the same level of performance as a card with external antennas?

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Network switching issues with MacOS 10.7?

- by Denis

I'm having a wired problem and hope somebody can tip me, what way should I dig to. I'm using MacBookPro with Lion 10.7.3 both at my working place & at home. At working place, we have a domain-based network with 802.1x authorization (more than 400 computers) and to connect it I'm using Ethernet cable. IP range is 10.10.2.*. All network settings are setup automatically by DHCP. Also, in settings, I have Network Account Server setup in the User&Groups Settings for my work Domain server - and it is available only from corporate network. At home, I have an ADSL router, that shares Internet connection by WiFi in NAT mode. I'm using WiFi to connect it. Router gives out addresses from 192.168.1.* range and all settings are also set up by router's DHCP. So, my problem is the following. When I come back home from the office, I open my MacBook and AirPort automatically connects my WiFi network. After this, for about 1 minute I'm able to browse sites & ping hosts successfully. But after this minute, network connection is broken down. All pings return time-out. trace route to google.com stops on 192.168.1.1 (which is my router). This lasts for 3-4 minutes. After that network connection is automatically repaired and all pings go smoothly again. At the same time, when my MacBook return timeouts, I can successfully ping any host from my wife's MacBook - so this doesn't look like router issue. When I come to the office, I don't have any issues and Internet connection is available & stable moments after ethernet cable plugged in. Do anybody has any clues about this? What should I monitor & what settings look for resolving this issue? Please, ask, what additional information should I provide. Hoping for good advice & thanks in advance!

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Connecting a print/file server with no wired access

- by PeanutsMonkey

We currently have a printer server which also serves as a file server. The server is located on premise however is not close to any wired access point i.e. a patch panel or point. The server also requires access to the Internet as it transmits files across. We have a wireless modem and a wireless router. I can run a cable between the server and wireless router. How can I have the wireless router communicate with the wireless modem? If the operating system of the server is concerned, it is running Windows Server 2003.

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Defining a persistent static route on Mac OS X

- by Charles Duffy

How does one define a static route on MacOS X which persists through reboots? The only suggestion I've found on Google advises setting up a launchd service to run at boot, which seems like a horrible hack (does it survive a network restart without rebooting, for instance?) To set up the route I need temporarily, I can run the following: route add -net ${network} ${gateway} ${netmask} How would I make this persist?

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Too many Tunnel Adapter Interfaces

- by Tomas Lycken

If I open a command prompt on my machine and type ipconfig /all, I see lots of Tunnel adapter Local Area Connection* 9: Media state . . . . . . . . . . . . . : Media disconnected Connection-specific DNS Sufficx . . . : Description . . . . . . . . . . . . . : Microsoft 6to4 Adapter #5 Physical address. . . . . . . . . . . : 00-00-00-00-00-00-00-E0 DHCP Enabled. . . . . . . . . . . . . : No Autoconfiguration Enabled . . . . . . : Yes In fact, they're so many that my "real" adapters are pushed out of the stack, and can't be seen anymore. Is there any flag I can use on ipconfig to hide all virtual interfaces? Or is there some other way around this problem? Since they always say "Media disconnected" I suppose disabling could be an option, but if possible I'd rather not turn any functionality off. I just want to control what output I get from ipconfig. Also, I know these are related to IPv6 stuff. However, most of what I find on google merely states what these are, and that they're harmless - nothing about hiding/removing them.

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Frequent and weird wifi disconnections

- by Sidou

How would you explain, troubleshoot (and solve) the following problem? Wifi ADSL modem router D-link 2640R installed in living room at about 1.8m height. Working fine, synchronising and getting/serving stable internet connection. First situation: -Laptop 01 in other end of the house, let's say in room01 southern to the living room, distant by about 15m. Getting stable signal of good to very good quality. No disconnection. -Laptop 02 in room02 opposite to room01 (5m West) which makes it almost at the same distance and direction from the router located 15m North. Getting stable signal of good to very good quality. No disconnection. Second situation: -Laptop 01 moved to room03 Northern to the living room (actually just 3m behind the wall where the router lies). Getting stable signal of excellent quality. No disconnection. -Laptop 02 still in room02 but now experiences frequent disconnections (actually almost impossible to get the Internet even though the signal level is still very good. Either no Internet with the wifi icon appearing connected to access point or no connection established at all which happens every 2 minutes and that means virtually no Internet at all as I can just get a timeframe of 1 minute or so to load any website or even get to the router's web based control panel. If Laptop 01 is completely shut down or its wifi adapters shut down or even still working but its wifi MAC address forbidden, then Laptop 02 has no problem at all. If Laptop 02 is moved to a nearer location to the router, in the living room for instance, then no connection problem occurs even if Laptop 01 is also connected. And also if we move back Laptop 01 to its original location (room 01), then no problem as well. I'm completely lost and don't know how to address this issue. I tried to change the Wifi channel and even tried the auto channel scan but that didn't solve it. I know that the problem is probably coming from Laptop 01 being in its new location or some sort of interference as the problem occurs only under the described condition but I have no idea how to solve it! I also scanned the neighborhood for wifi jam using InSSIDer, there are few other access points but they don't seem to affect the situation. Any ideas about the steps to follow or tools to use ?

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How secure is a subnet?

- by HorusKol

I have an unfortunate complication in my network - some users/computers are attached to a completely private and firewalled office network that we administer (10.n.n.x/24 intranet), but others are attached to a subnet provided by a third party (129.n.n.x/25) as they need to access the internet via the third party's proxy. I have previously set up a gateway/router to allow the 10.n.n.x/24 network internet access: # Allow established connections, and those !not! coming from the public interface # eth0 = public interface # eth1 = private interface iptables -A INPUT -m state --state ESTABLISHED,RELATED -j ACCEPT iptables -A INPUT -m state --state NEW ! -i eth0 -j ACCEPT iptables -A FORWARD -i eth0 -o eth1 -m state --state ESTABLISHED,RELATED -j ACCEPT # Allow outgoing connections from the private interface iptables -A FORWARD -i eth1 -o eth0 -j ACCEPT # Masquerade (NAT) iptables -t nat -A POSTROUTING -o eth0 -j MASQUERADE # Don't forward any other traffic from the public to the private iptables -A FORWARD -i eth0 -o eth1 -j REJECT However, I now need to enable access to users on our 129.n.n.x/25 subnet to some private servers on the 10.n.n.x/24 network. I figured that I could do something like: # Allow established connections, and those !not! coming from the public interface # eth0 = public interface # eth1 = private interface #1 (10.n.n.x/24) # eth2 = private interface #2 (129.n.n.x/25) iptables -A INPUT -m state --state ESTABLISHED,RELATED -j ACCEPT iptables -A INPUT -m state --state NEW ! -i eth0 -j ACCEPT iptables -A FORWARD -i eth0 -o eth1 -m state --state ESTABLISHED,RELATED -j ACCEPT iptables -A FORWARD -i eth0 -o eth2 -m state --state ESTABLISHED,RELATED -j ACCEPT # Allow outgoing connections from the private interfaces iptables -A FORWARD -i eth1 -o eth0 -j ACCEPT iptables -A FORWARD -i eth2 -o eth0 -j ACCEPT # Allow the two public connections to talk to each other iptables -A FORWARD -i eth1 -o eth2 -j ACCEPT iptables -A FORWARD -i eth2 -o eth1 -j ACCEPT # Masquerade (NAT) iptables -t nat -A POSTROUTING -o eth0 -j MASQUERADE # Don't forward any other traffic from the public to the private iptables -A FORWARD -i eth0 -o eth1 -j REJECT iptables -A FORWARD -i eth0 -o eth2 -j REJECT My concern is that I know that the computers on our 129.n.n.x/25 subnet can be accessed via a VPN through the larger network operated by the provider - therefore, would it be possible for someone on the provider's supernet (correct term? inverse of subnet?) to be able to access our private 10.n.n.x/24 intranet?

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How to Configure Different Gateways for Different VLANs

- by Bryan

I have around 10 VLANs, and two different internet gateways. I want traffic on some VLANs to use one gateway, and traffic on other VLANs to use another gateway. (e.g. I wish to route server traffic via one gateway and desktop internet traffic down another). Is it possible to configure different default routes for different VLANs on a Dell 6224 switch? Or is their a better way of doing what I'm trying to achieve? The core switch I am using is a Dell PowerConnect 6224 switch. Currently I'm using: ip route 0.0.0.0 0.0.0.0 10.58.3.16 which creates the default gateway for all VLANs. I did consider adding multiple routes with equal metric, and setting ACLs between the VLANs to deny access to the 'wrong' gateway, but that idea just doesn't feel right to me.

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Why Would one VLAN have no Communication on one Switch?

- by Webs

So the problem is we have a device or host that needs to communicate on a specific VLAN. This VLAN is not new, it is running all throughout our environment and works fine. But the VLAN was recently configured on the switch in question, a Cisco 3750. The DHCP server is handing out addresses on that VLAN with no problem. I have verified the cable between the host and switch and tried multiple hosts, but none of them can communicate or get an address. I plugged my laptop into an empty port which had a different VLAN assigned and immediately got a DHCP address. When I changed that port to the same VLAN I'm having issues with I got the same problem. The laptop just sits there and tries to DHCP an address but nothing happens. I double checked the cores and their Layer 3 VLAN config and its fine too. Plus I figured the issue couldn't be with them because the VLAN works fine everywhere else it exists. So the only other thing I can think of is the switch, but the VLAN exists on the switch and seems to be configured correctly. The trunks appear to be configured just fine as well too. Anyone have any ideas? I'm lost on this one.

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Redirection of outbound UDP port.

- by pboin

For my residential service, I changed ISPs to Zoom/Armstrong. Just after that, my NTP daemons stopped working. I dug deep and diagnosed the problem: Unprivileged ports are getting out. When i run 'ntpdate' for example, I go out on a high, unprivleged port, and get a response on UDP 123. That's fine. The 'ntpd' daemon though, expects to go out on 123 and get its reply there as well. This must be a common problem, because it's directly addressed in the NTP troubleshooting guide. Just to see what would happen, I wrote a detailed email to the general support address at Armstrong. They replied almost immediately with a complete technical answer! They have everything <1024 blocked, except for a few ports to support outbound VPN. So, the question: Can I use IPtables to essentially re-write my outbound UDP 123 up to 2123 or something like that? If I do, does there need to be a corresponding 2123-123 rule to translate the reply? This seems like NAT, but with ports, not addresses. I tried, but can't seem to get iptables to do what I want. I'm not sure if it's my lack of skill, or if I'm trying the wrong solution. True, I could run ntpdate from cron, but that loses all of the adjustment smarts of NTP.

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Cannot increase MTU on gigabit network

- by RayQuang

Hi, I have just set up my new gigabit network and when I was about to increase the MTU to use jumbo frames, I get this error: root@rayquang-desktop:~# ifconfig eth1 mtu 9000 SIOCSIFMTU: Invalid argument Could anyone help me to increase the MTU. Details: NIC: NETGEAR GA311; Switch: NETGEAR GS105, running Ubuntu 10.10 and Debian Lenny on desktop, server respectively. Help would be greatly appreciated, RayQuang

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