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Why might one host be unable to access the Internet, when it can ping the router and when all other hosts can?

- by user1444233

I have a Draytek Vigor 2830n. It's kicking out a 192.168.3.0 LAN. It performs load-balancing across dual-WAN ports, although I've turned off the second WAN to simplify testing. There are many hosts on the LAN. All IPs are allocated through DHCP, most freely allocated from the pool, but one or two are bound to NIC MAC addresses. All hosts can access the Internet, save one. That host (192.168.3.100 or 'dot100' for short) gets allocated an IP address (and the right gateway address, DNS server addresses, subnet etc.) dot100 can ping itself. It can ping the gateway, and access the latter's web interface via port 80. It's responsive and loss-free (sustained ping over a couple of minutes reports no data loss). Yet, for some reason that evades me, dot100 can't ping an external IP address or domain name. I suspect it's never been able to, because it was getting some Internet access from a second adaptor (different subnet), but that's now been turned off, which exposed the problem. In dot100, I've tried: two operating systems (Windows 8 and Knoppix), to rule out anti-virus programs etc. two physical adaptors two cables, on each adaptor two IPs (e.g. .100 and .103 assigned by Mac and .26 from the pool) both dynamic and assigned (MAC-bound) DHCP-allocated IPs but none of this experiments yielded any variation in the result. dot100 is a crucial host. It's a file server for the network, so I need it to be reliably allocated a consistent IP. Can anyone offer a potential solution or a way forward with the analysis please? My guess My analysis so far leads me to believe it's a router issue. I've checked the web interface very carefully. There are no filters setup in Firewall - General Setup or Filter Setup. I suspect it's a corrupted internal routing table, but the web UI shows this as the Routing table: Key: C - connected, S - static, R - RIP, * - default, ~ - private * 0.0.0.0/ 0.0.0.0 via 62.XX.XX.X WAN1 * 62.XX.XX.X/ 255.255.255.255 via 62.XX.XX.X WAN1 S 82.YY.YYY.YYY/ 255.255.255.255 via 82.YY.YYY.YYY WAN1 C 192.168.1.0/ 255.255.255.0 directly connected WAN2 C~ 192.168.3.0/ 255.255.255.0 directly connected LAN2

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Real benefits of tcp TIME-WAIT and implications in production environment

- by user64204

SOME THEORY I've been doing some reading on tcp TIME-WAIT (here and there) and what I read is that it's a value set to 2 x MSL (maximum segment life) which keeps a connection in the "connection table" for a while to guarantee that, "before your allowed to create a connection with the same tuple, all the packets belonging to previous incarnations of that tuple will be dead". Since segments received (apart from SYN under specific circumstances) while a connection is either in TIME-WAIT or no longer existing would be discarded, why not close the connection right away? Q1: Is it because there is less processing involved in dealing with segments from old connections and less processing to create a new connection on the same tuple when in TIME-WAIT (i.e. are there performance benefits)? If the above explanation doesn't stand, the only reason I see the TIME-WAIT being useful would be if a client sends a SYN for a connection before it sends remaining segments for an old connection on the same tuple in which case the receiver would re-open the connection but then get bad segments and and would have to terminate it. Q2: Is this analysis correct? Q3: Are there other benefits to using TIME-WAIT? SOME PRACTICE I've been looking at the munin graphs on a production server that I administrate. Here is one: As you can see there are more connections in TIME-WAIT than ESTABLISHED, around twice as many most of the time, on some occasions four times as many. Q4: Does this have an impact on performance? Q5: If so, is it wise/recommended to reduce the TIME-WAIT value (and what to)? Q6: Is this ratio of TIME-WAIT / ESTABLISHED connections normal? Could this be related to malicious connection attempts?

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Ubuntu 12.04 suddenly cannot connect to WPA2/WPA Personal protected connection. Windows 7 can

- by d4ryl3

I have a laptop with Windows 7 and Ubuntu 12.04. I have a Cisco E1200 and when I set it up, it created 2 SSIDs. Let's name them: MyConnection (WPA/WPA2 personal), and MyConnection-Guest (no authentication, guest password entered via web browser). I had no problem connecting to MyConnection before, either in Windows 7 and Ubuntu. But now, I can't access MyConnection on Ubuntu. It just says "connecting..." then disconnects after a while. But I'm able to access the internet (on Ubuntu) when I connect to MyConnection-Guest. MAC filtering is off (even if it's on its MAC address is in the white list). Any idea why I'm unable to connect to MyConnection in Ubuntu? Thanks. Update: My Ubuntu installation can connect to ANY WiFi connection (WPA/WEP/no auth), except for MyConnection. Update2: This is what "The not so easy way" returned: Initializing interface 'eth1' conf '/etc/wpa_supplicant.conf' driver 'default' ctrl_interface 'N/A' bridge 'N/A' Configuration file '/etc/wpa_supplicant.conf' -> '/etc/wpa_supplicant.conf' Reading configuration file '/etc/wpa_supplicant.conf' Priority group 0 id=0 ssid='MyConnection' id=1 ssid='MyConnection' id=2 ssid='MyConnection' id=3 ssid='MyConnection' WEXT: cfg80211-based driver detected SIOCGIWRANGE: WE(compiled)=22 WE(source)=21 enc_capa=0xf capabilities: key_mgmt 0xf enc 0xf flags 0x0 netlink: Operstate: linkmode=1, operstate=5 Own MAC address: xx:xx:xx:xx:xx:xx wpa_driver_wext_set_key: alg=0 key_idx=0 set_tx=0 seq_len=0 key_len=0 wpa_driver_wext_set_key: alg=0 key_idx=1 set_tx=0 seq_len=0 key_len=0 wpa_driver_wext_set_key: alg=0 key_idx=2 set_tx=0 seq_len=0 key_len=0 wpa_driver_wext_set_key: alg=0 key_idx=3 set_tx=0 seq_len=0 key_len=0 wpa_driver_wext_set_key: alg=0 key_idx=4 set_tx=0 seq_len=0 key_len=0 ioctl[SIOCSIWENCODEEXT]: Invalid argument Driver did not support SIOCSIWENCODEEXT wpa_driver_wext_set_key: alg=0 key_idx=5 set_tx=0 seq_len=0 key_len=0 ioctl[SIOCSIWENCODEEXT]: Invalid argument Driver did not support SIOCSIWENCODEEXT wpa_driver_wext_set_countermeasures RSN: flushing PMKID list in the driver Setting scan request: 0 sec 100000 usec WPS: UUID based on MAC address - hexdump(len=16): 16 3b d8 47 9e 24 50 89 96 16 6d 66 35 f3 58 37 EAPOL: SUPP_PAE entering state DISCONNECTED EAPOL: Supplicant port status: Unauthorized EAPOL: KEY_RX entering state NO_KEY_RECEIVE EAPOL: SUPP_BE entering state INITIALIZE EAP: EAP entering state DISABLED EAPOL: Supplicant port status: Unauthorized EAPOL: Supplicant port status: Unauthorized Added interface eth1

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Default gateway is in different subnet. How to configure in RHEL6.2

- by Dmytro Leonenko

I have two subnets routed to my server from ISP. I have only one gateway ip. The gateway is on the same VLAN as my IP address. For example netowrk 1 is 1.0.0.0/24 and network 2 is 2.0.0.0/24. Both are routed to eth0 by my ISP. Gateway is 1.0.0.1. My host ip is 2.0.0.1/24 (eth0) So I can configure default gateway manually with ip route add default dev eth0 ip route add default via 1.0.0.1 and then internet connection works properly. How do I configure it in /etc/sysconfig/network-scripts/ifcfg-eth0 ? I tried to set GATEWAY=1.0.0.1 but it doesn't work. Tried to set GATEWAY and GATEWAYDEV in /etc/sysconfig/network and it does only what first command from listing above do.

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How to monitor the network traffic on a router?

- by Adi

Here's my current network set-up: we have 3 users connecting to a Thomson Gateway router (TG585 v8) provided by my ISP. We are connecting over an ADSL line. The problem is that we have a limited data allowance (60GB) and we always exceed it. I would like to monitor how much traffic each computer makes. The best solution would be to install a software on the router (like OpenWRT) which would monitor how much traffic each computer makes. But I couldn't find any replacement firmware that would support my router. The other solution would be to install a software on each machine and then collect all the data at the end of the mount. But that's not a very good think to do. Plus, the users can always shut down the application. Any suggestions?

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msi netbook refuses to connect to home wireless network (windows xp)

- by sa125

Hi - I'm trying to connect my girlfriend's MSI netbook to the wireless network in my house, and failing repeatedly. It's not a hardware issue, b/c it connects to other networks successfully, and, it's not a network issue, because I have another mac and linux laptops that have no problem detecting and connecting to the same network. When I open windows' network connections box, I can see the network available, and when I try to connect to it (using a password), I get a "network no longer in range.." error (the router is 2 ft away). This has been the case for the past 6 months, and I'm about to give up. I've reset the router, erased all saved network preferences and pretty much all I could think of short of re-installing XP. Any idea what else could be done? thanks.

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Know which Apps to Remove From MSConfig with this Startup Applications List

- by Mit Naik

Just found userfull information on Internet and thought it would help all of users. This list of startup applications is a really handy resource for cleaning up msconfig entries that have overtaken old computers. It catalogs tons of different startup programs, what they do, and which ones you should delete, leave running, or decide based on the program's usefulness. It even has a nice search box so you can search through the tens of thousands of entries. Hit the link below to check it out, and if your relatives' computer is especially broken, be sure to check out our guide to fixing your relatives' terrible computer. http://www.sysinfo.org/startuplist.php Please update the list here if you got any other tools or sites which can be help full to others

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What do you use to loadbalance IPv6 services?

- by Michael Renner

Hi, the current Linux software environment for IPv6 load balancing looks a bit grim. IPVS has rudimentary support for IPv6 but it's far from complete. NAT for IPv6 seems to be a no-go. Are there any other projects which aim for this goal? Does the IPv6 support in other OS look better? Are there any commercial products which have been successfully used in production environments with non-trivial load patterns? Or is it just that the time for IPv6 hasn't come... yet? ;) best regards, Michael

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Ubuntu with KVM guest VM and broken bridges

- by MadPsy

I have an Ubuntu box with a KVM guest VM running. They use bridging so the guest VM attaches to the physical network of its host. The guest VM has 2 NICs in 2 different bridges. First NIC of the VM is tap5 and is in bridge br0 br0 8000.46720f5c572e no eth0.500 tap5 Second NIC of the VM is tap2 and is in bridge br100 br100 8000.76ad2fc96661 no eth0.100 eth0.101 eth0.103 eth0.104 eth0.105 tap2 On the host, br0 has an IP and br100 does not 21: br0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc noqueue state UP link/ether 46:72:0f:5c:57:2e brd ff:ff:ff:ff:ff:ff inet 192.168.100.4/24 brd 192.168.10.255 scope global br0 inet6 fe80::d6ae:52ff:febe:777/64 scope link valid_lft forever preferred_lft forever On the guest, its eth0 and eth1 interfaces both have IP addresses 2: eth0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast state UP qlen 1000 link/ether 00:3e:61:fb:7a:da brd ff:ff:ff:ff:ff:ff inet 192.168.100.6/24 brd 192.168.100.255 scope global eth0 inet6 fe80::23e:61ff:fefb:7ada/64 scope link valid_lft forever preferred_lft forever 3: eth1: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast state UP qlen 1000 link/ether 00:3e:61:fb:7a:ea brd ff:ff:ff:ff:ff:ff inet 172.16.50.129/25 brd 172.16.50.255 scope global eth1 inet6 fe80::23e:61ff:fefb:7aea/64 scope link valid_lft forever preferred_lft forever On the guest VM, a tcpdump of its eth1 interface (tap2) shows traffic from its eth0 interface (tap5), as if the 2 bridges are themselves bridged. This means any interface on br100 is now bridged across to br0 - which is completely broken. root@chillispot:~# tcpdump -c 1 -n -v -i eth1 net 192.168.100.0/24 tcpdump: listening on eth1, link-type EN10MB (Ethernet), capture size 65535 bytes 16:31:24.175583 IP (tos 0x0, ttl 64, id 48054, offset 0, flags [DF], proto TCP (6), length 148) 192.168.100.6.22 > 192.168.100.4.59505: Flags [P.], cksum 0x6c2b (correct), seq 1056321648:1056321744, ack 398642983, win 1700, options [nop,nop,TS val 197473436 ecr 200655363], length 96 What could be bridging the 2 bridges, except the guest VM (which is a stock Ubuntu install)? I am at a complete loss! Thanks.

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How should I set up my Hyper-V server and network topology?

- by Daniel Waechter

This is my first time setting up either Hyper-V or Windows 2008, so please bear with me. I am setting up a pretty decent server running Windows Server 2008 R2 to be a remote (colocated) Hyper-V host. It will be hosting Linux and Windows VMs, initially for developers to use but eventually also to do some web hosting and other tasks. Currently I have two VMs, one Windows and one Ubuntu Linux, running pretty well, and I plan to clone them for future use. Right now I'm considering the best ways to configure developer and administrator access to the server once it is moved into the colocation facility, and I'm seeking advice on that. My thought is to set up a VPN for access to certain features of the VMs on the server, but I have a few different options for going about this: Connect the server to an existing hardware firewall (an old-ish Netscreen 5-GT) that can create a VPN and map external IPs to the VMs, which will have their own IPs exposed through the virtual interface. One problem with this choice is that I'm the only one trained on the Netscreen, and its interface is a bit baroque, so others may have difficulty maintaining it. Advantage is that I already know how to do it, and I know it will do what I need. Connect the server directly to the network and configure the Windows 2008 firewall to restrict access to the VMs and set up a VPN. I haven't done this before, so it will have a learning curve, but I'm willing to learn if this option is better long-term than the Netscreen. Another advantage is that I won't have to train anyone on the Netscreen interface. Still, I'm not certain if the capabilities of the Windows software firewall as far as creating VPNs, setting up rules for external access to certain ports on the IPs of Hyper-V servers, etc. Will it be sufficient for my needs and easy enough to set up / maintain? Anything else? What are the limitations of my approaches? What are the best practices / what has worked well for you? Remember that I need to set up developer access as well as consumer access to some services. Is a VPN even the right choice?

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How do i set up a fully featured small business network?

- by JoshReedSchramm

This has the possibility to be a very large question but I recently acquired a few rack mount servers and the hardware necessary to run them. Unfortunately I'm a programmer with very little understanding of how to set up a good working network so I'm hoping someone on here might be able to help. What I want to do is run a domain with a series of subdomains which would all be externally accessible. The setup would live inside my home and my internet connection is your run of the mill cable model (which means a dynamic IP) I want to be able to set up a couple site, specifically: www.mycompany.com (mycompany.com with no subdomain would redirect to this) build.mycompany.com (for my continuous integration server) ruby.mycompany.com (for ruby projects) win.mycompany.com (for windows project) etc. Additionally this is still my home network so our personal machines need to be able to get on via wifi with at least the same security we have now through an out of the box router from best buy. I'm thinking i need a DNS server, DHCP server and one of those would run either no-ip or dyndns to accommodate the dynamic ip. I don't necessarily need mail but it might be helpful to have some sort of mail server i could use for testing, it doesn't need to get out to the greater internet though. So how do i set up this kinda of network? tl;dr Need to know how to set up your standard office style network in my home off my normal consumer level cable modem connection.

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Windows Hosted Network Redirect to IIS

- by rulestein

I would like to setup a Windows 7 machine as a wifi hotspot that always redirects to the IIS web hosting on the same machine. I have the hotspot piece working with the built in hosted network of Widnows 7. The webhosting was easy enough with IIS. Now, how do I connect the 2? The idea is to have a standalone device that users will be able to connect to the wifi and any webpage they go to will redirect to the internal webpage. I only expect 1 or 2 users at a time and there won't be any internet access involved.

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How can I unregister a service with dns-sd?

- by Roman

I am trying to use "dns-sd" command line tool on my Windows 7 machine. I can already do something. For example I can register a service using "dns-sd -R ...". I also can browser (see) registered services using "dns-sd -B ...". What I still miss, is how to unregister a service. At the moment when I type "dns-sd -R ..." the dns-sd does not return me to the command prompt. To return to the command prompt I need to press Ctrl-C. And the service stays registered till I press Ctrl-C. What I want is to run "dns-sd -R ..." in the background regime and then I would like to have a possibility to unregister a service from the command line. One more thing which I do not understand yet is what "to look up a service" means. In my picture it should be sufficient to register a service, to see it and then to unregister it. But apparently I need to look up a service. What does it mean and why I need to do it?

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OpenVPN on Tomato and Vista - can't see my network

- by Ian

I followed the instructions here (http://todayguesswhat.blogspot.ca/2011/03/quick-simple-vpn-setup-guide-using.html) to set up a TCP connection to OpenVPN on my Tomato router. Used TCP because the place I usually surf at seems to have the other ports blocked. My Vista laptop is able to connect to the router but I don't appear to be getting an IP address. I'm able to access my router's admin page, but I can't see the network at home. When I browse to Whatsmyip I see my home IP. Here are the results of route print -4 when I'm just connect to the library and when I've fired up the VP connection as well: Library only: =========================================================================== Interface List 22 ...00 ff c4 a0 e7 5c ...... TAP-Win32 Adapter V9 15 ...00 23 4e 20 b3 64 ...... Atheros AR9281 Wireless Network Adapter 10 ...00 23 8b 39 ec 71 ...... Marvell Yukon 88E8040T PCI-E Fast Ethernet Controller 1 ........................... Software Loopback Interface 1 11 ...00 00 00 00 00 00 00 e0 isatap.{834A8A0A-5E2C-47D0-9673-7965DE8B5470} 14 ...02 00 54 55 4e 01 ...... Teredo Tunneling Pseudo-Interface 17 ...00 00 00 00 00 00 00 e0 Microsoft ISATAP Adapter #3 20 ...00 00 00 00 00 00 00 e0 6TO4 Adapter 18 ...00 00 00 00 00 00 00 e0 6TO4 Adapter 19 ...00 00 00 00 00 00 00 e0 6TO4 Adapter 23 ...00 00 00 00 00 00 00 e0 isatap.{C4A0E75C-765E-4F7D-A55C-77945779816A} 34 ...00 00 00 00 00 00 00 e0 Microsoft ISATAP Adapter #5 =========================================================================== IPv4 Route Table =========================================================================== Active Routes: Network Destination Netmask Gateway Interface Metric 0.0.0.0 0.0.0.0 10.1.29.1 10.1.29.117 25 10.1.29.0 255.255.255.0 On-link 10.1.29.117 281 10.1.29.117 255.255.255.255 On-link 10.1.29.117 281 10.1.29.255 255.255.255.255 On-link 10.1.29.117 281 127.0.0.0 255.0.0.0 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 127.0.0.1 306 224.0.0.0 240.0.0.0 On-link 127.0.0.1 306 224.0.0.0 240.0.0.0 On-link 10.1.29.117 281 255.255.255.255 255.255.255.255 On-link 127.0.0.1 306 255.255.255.255 255.255.255.255 On-link 10.1.29.117 281 =========================================================================== Library and TCP OpenVPN: IPv4 Route Table =========================================================================== Active Routes: Network Destination Netmask Gateway Interface Metric 0.0.0.0 0.0.0.0 10.1.29.1 10.1.29.117 25 0.0.0.0 0.0.0.0 192.168.1.1 192.168.1.116 30 0.0.0.0 128.0.0.0 192.168.1.1 192.168.1.116 30 10.1.29.0 255.255.255.0 On-link 10.1.29.117 281 10.1.29.117 255.255.255.255 On-link 10.1.29.117 281 10.1.29.255 255.255.255.255 On-link 10.1.29.117 281 24.212.205.68 255.255.255.255 10.1.29.1 10.1.29.117 25 127.0.0.0 255.0.0.0 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 127.0.0.1 306 128.0.0.0 128.0.0.0 192.168.1.1 192.168.1.116 30 192.168.1.0 255.255.255.0 On-link 192.168.1.116 286 192.168.1.116 255.255.255.255 On-link 192.168.1.116 286 192.168.1.255 255.255.255.255 On-link 192.168.1.116 286 224.0.0.0 240.0.0.0 On-link 127.0.0.1 306 224.0.0.0 240.0.0.0 On-link 192.168.1.116 286 224.0.0.0 240.0.0.0 On-link 10.1.29.117 281 255.255.255.255 255.255.255.255 On-link 127.0.0.1 306 255.255.255.255 255.255.255.255 On-link 192.168.1.116 286 255.255.255.255 255.255.255.255 On-link 10.1.29.117 281 =========================================================================== Thanks for any advice. I looked at one of the answers but I'm not sure if it applied to me as it said that 10...* was the vpn connection, but I appear to have 10...* when I connect just to the library.

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Is it possible to provide a wired ethernet connection to external devices with an extra LAN card?

- by Ben McCormack

I'm trying to provide a wired ethernet connection (wireless is not an option for this device) to a device (Samsung blu-ray player) without running Cat5 cable all over the home. I have a PC sitting next to this device and the PC is connected to the network via a wireless USB adapter. Is it possible to provide a wired connection from the PC to the wired device using the (currently unused) ethernet port in the back of the computer? Here's how I envision the device getting connected to the internet via my network: Linksys WRT54G v8 Wireless Router | ``--> Windows 7 PC connected via wireless | ``--> Blu-ray player connected via wired connection to the ethernet port on the PC. If so, how is this done? Will I need a crossover cable? What settings will I need to change in Windows 7 so that the device can connect? NOTE: I'm trying to avoid having to buy a wireless bridge and/or hacking a router with an open-source firmware to get this to work. See my previous question for more details.

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Most awesomely bad hack

- by Zypher

As I sit watching one of my latest dirty dirty hacks run, I started wondering what kind of dirty hacks you have created that are so bad they are awesome. We all have a few of them in our past - and they are probably still running in production somewhere, chugging along somehow still working. Which reminds me of the hack we had to put into place when we were moving data centers. Our IVRs had to keep running, as the data center we were moving from was the primary DC, and the new Primary wasn't quite ready to take traffic. So what do we do. Well we answer the calls in DC1, then ship the sip stream over the internet to DC2 1900 miles away ... that just felt oh so wrong. So the question is, what is one (or more) of your awesomely bad hacks?

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My internet drops and will only reconnect if I troubleshoot it or restart my computer.

- by Paul

My internet loses its connection and at the same time, and my speaker seems broken if that happens and my mouse will not be smooth as it was before it happens. It already happened before and I didnt mind it. But now, it's happening literally all the time. After startup, my connection seems okay but after some few minutes, even without me doing something, my laptop will just lose its connection. It says that it is not connected and connections are available, but if I check if there are connections where I can connect it shows nothing. Even if, there is actually a wi-fi connection where my phone and other laptops connect. They dont seem to have problem with it. Just my laptop. After that happens, I usually restart my laptop but I discovered that troubleshooting it would somehow repair the problem, but not all the time. It says that restarting my wireless adapter do the job. Are there any long term fix? I mean that could last long or totally erase the problem? I have Atheros AR5B97 Wireless Network Adapter and Microsoft Virtual WiFi Miniport Adapter, both enabled. On the services, I have Wired AutoConfig and WLAN AutoConfig on Automatic. Aspire 4750, Windows 7 (x86)

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Managing an application across multiple servers, or PXE vs cfEngine/Chef/Puppet

- by matt

We have an application that is running on a few (5 or so and will grow) boxes. The hardware is identical in all the machines, and ideally the software would be as well. I have been managing them by hand up until now, and don't want to anymore (static ip addresses, disabling all necessary services, installing required packages...) . Can anyone balance the pros and cons of the following options, or suggest something more intelligent? 1: Individually install centos on all the boxes and manage the configs with chef/cfengine/puppet. This would be good, as I have wanted an excuse to learn to use one of applications, but I don't know if this is actually the best solution. 2: Make one box perfect and image it. Serve the image over PXE and whenever I want to make modifications, I can just reboot the boxes from a new image. How do cluster guys normally handle things like having mac addresses in the /etc/sysconfig/network-scripts/ifcfg* files? We use infiniband as well, and it also refuses to start if the hwaddr is wrong. Can these be correctly generated at boot? I'm leaning towards the PXE solution, but I think monitoring with munin or nagios will be a little more complicated with this. Anyone have experience with this type of problem? All the servers have SSDs in them and are fast and powerful. Thanks, matt.

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Windows 2008 R2 Servers Sending Arp Requests for IPs outside Subnet

- by Kyle Brandt

By running a packet capture on my my routers I see some of my servers sending ARP requests for IPs that exist outside of its network. For example if my network is: Network: 8.8.8.0/24 Gateway: 8.8.8.1 (MAC: 00:21:9b:aa:aa:aa) Example Server: 8.8.8.20 (MAC: 00:21:9b:bb:bb:bb) By running a capture on the interface that has 8.8.8.1 I see requests like: Sender Mac: 00:21:9b:bb:bb:bb Sender IP: 8.8.8.20 Target MAC: 00:21:9b:aa:aa:aa Target IP: 69.63.181.58 Anyone seen this behavior before? My understanding of ARP is that requests should only go out for IPs within the subnet... Am I confused in my understanding of ARP? If I am not confused, anyone seen this behavior? Also, these seem to happen in bursts and it doesn't happen when I do something like ping an IP outside of the network. Update: In response to Ian's questions. I am not running anything like Hyper-V. I have multiple interfaces but only one is active (Using BACS failover teaming). The subnet mask is 255.255.255.0 (Even if it were something different it wouldn't explain an IP like 69.63.181.58). When I run MS Network Monitor or wireshark I do not see these ARP requests. What happens is that on the router capturing I see a burst of about 10 requests for IPs outside of the network from the host machine. On the machine itself using wireshark or NetMon I see a flood of ARP responses for all the machines on the network. However, I don't see any requests in the capture asking for those responses. So it seems like maybe it is maybe refreshing the arp cache but including IPs that outside of the network. Also when it does this NetMon doesn't show the ARP requests?

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Win 2k3 - DNS query ?

- by nXqd

I'm learning about network and I configured DNS in 2k3. In forward zone : cntt.edu www.cntt.edu [ 192.168.188.4 ] . [ All IP / DNS configuration is right ] After that I use wireshark to catch packet when I enter www.cntt.edu in IE . I see there's no DNS here, I forward directly to 192.168.188.4, there's no query . Any problem ? Thanks for reading this :)

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Troubleshooting Website problems within the local network

- by HaydnWVN

Have an external website which opens fine on some PC's, yet seems to time out (or symptoms of timing out, but never actually does) on others. Seems to only affect (some) of our newer HP Pro 3305 MT Workstations. All of which are running Win7 32bit SP1 with all updates. Older PC's (Win7 32bit SP1 & WinXP) are unaffected. Using Google Chrome & Firefox makes no difference. Opening the website in IE9 Compatibility Mode has exactly the same symptoms. All PC's are on the same local network (Workgroup) using the same DNS server & gateway (inhouse) on the same internet connection, on the same subnet. There is no proxy server, no content filtering, no load balancing etc etc. Only group policy in effect (locally) is for Update scheduling. Local firewalls are all the same (Kaspersky WP4) and our external facing firewall has no IP specific settings. I have no control over the external website, traceroute shows the same destination on all PC's. It is a fairly popular website in our industry (Horticulture) and i'm not aware of any other people (even other sites within our sister companies) with the same problem. Update: Used Fiddler2 to monitor the HTTP request, seems its not getting fulfilled for some reason?! Request sent: GET http://www.rhs.org.uk/ HTTP/1.1 Host: www.rhs.org.uk Connection: keep-alive User-Agent: Mozilla/5.0 (Windows NT 6.1) AppleWebKit/536.11 (KHTML, like Gecko) Chrome/20.0.1132.47 Safari/536.11 Accept: text/html,application/xhtml+xml,application/xml;q=0.9,*/*;q=0.8 Accept-Encoding: gzip,deflate,sdch Accept-Language: en-GB,en-US;q=0.8,en;q=0.6 Accept-Charset: ISO-8859-1,utf-8;q=0.7,*;q=0.3 Log from Fiddler 2 of the request: This session is not yet complete. Press F5 to refresh when session is complete for updated statistics. Request Count: 1 Bytes Sent: 567 (headers:567; body:0) Bytes Received: 0 (headers:0; body:0) ACTUAL PERFORMANCE -------------- ClientConnected: 17:02:33.720 ClientBeginRequest: 17:02:39.118 GotRequestHeaders: 17:02:39.118 ClientDoneRequest: 17:02:39.118 Determine Gateway: 0ms DNS Lookup: 0ms TCP/IP Connect: 46ms HTTPS Handshake: 0ms ServerConnected: 17:02:39.165 FiddlerBeginRequest: 17:02:39.165 ServerGotRequest: 17:02:39.165 ServerBeginResponse: 00:00:00.000 GotResponseHeaders: 00:00:00.000 ServerDoneResponse: 00:00:00.000 ClientBeginResponse: 00:00:00.000 ClientDoneResponse: 00:00:00.000 RESPONSE BYTES (by Content-Type) -------------- ~headers~: 0 Log of a successful request from a working PC (done this morning, excuse the timestamps being different from above): Request Count: 1 Bytes Sent: 493 (headers:493; body:0) Bytes Received: 20,413 (headers:525; body:19,888) ACTUAL PERFORMANCE -------------- ClientConnected: 08:22:47.766 ClientBeginRequest: 08:22:47.766 GotRequestHeaders: 08:22:47.766 ClientDoneRequest: 08:22:47.766 Determine Gateway: 0ms DNS Lookup: 26ms TCP/IP Connect: 30ms HTTPS Handshake: 0ms ServerConnected: 08:22:47.828 FiddlerBeginRequest: 08:22:47.828 ServerGotRequest: 08:22:47.828 ServerBeginResponse: 08:22:48.905 GotResponseHeaders: 08:22:48.905 ServerDoneResponse: 08:22:48.905 ClientBeginResponse: 08:22:48.905 ClientDoneResponse: 08:22:48.905 Overall Elapsed: 00:00:01.1388020 RESPONSE BYTES (by Content-Type) -------------- text/html: 19,888 ~headers~: 525 So my question has evolved into: What is the difference between the 2 requests and how do I determine why 1 PC is not getting a reply to it's GET request?

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CentOS: eth0 not starting on boot

- by Cameron Aziz

Whenever I reboot a CentOS Hyper-V VM, eth0 does not start automatically. All I need to do is perform ifup eth0 and all is fixed, but that isn't feasible from ssh! I am starting in runlevel 3. After I perform ifup eth0 on the console: [root@localhost ~]# ifconfig eth0 Link encap:Ethernet HWaddr 00:15:5D:2B:2B:07 inet addr:10.10.0.3 Bcast:10.10.0.255 Mask:255.255.255.0 inet6 addr: fe80::215:5dff:fe2b:2b07/64 Scope:Link UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1 RX packets:34 errors:0 dropped:0 overruns:0 frame:0 TX packets:49 errors:0 dropped:0 overruns:0 carrier:0 collisions:0 txqueuelen:1000 RX bytes:4656 (4.5 KiB) TX bytes:6399 (6.2 KiB) Interrupt:9 Base address:0xa000 [root@localhost ~]# cat /etc/sysconfig/network-scripts/ifcfg-eth0 DEVICE=eth0 BOOTPROTO=none IPADDR=10.10.0.3 NETMASK=255.255.255.0 GATEWAY=10.10.0.1 USERCTL=no ONBOOT=yes [root@localhost ~]# chkconfig --list | grep network network 0:off 1:off 2:on 3:on 4:on 5:on 6:off

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Windows 7 VPN Error 619

- by TravisPUK

So I am running Windows 7 Enterprise. This morning I was able to VPN using the built in VPN (Connect to Work Network etc). I had to change my network's IP address range and now the VPN will not work. It just stalls on the Verifying user name and password... message. But then it returns the 619 error. Anybody know why changing my machine's IP address would cause this problem? Where should I be looking to try and fix this issue? I have tried this on a Windows XP machine that also had the IP address range change and this still connects fine using exactly the same connection details. EDIT The internal network range changed from 192.x.x.x to 10.x.x.x. This was done on the entire Active Directory. All machines are running fine and the Windows XP machine, that works going to the same client VPN mentioned above is on the same network. Both the XP and the Win 7 machines are using DHCP served by the Domain Controller. The client domain is not performing any IP range checks/restrictions. The VPN is outside the internal network, connection is being made via the Internet and not passing through any other machine, other than the normal domain machines, ie DNS etc. This is passing through a router and the router has the relevant VPN passthrough options configured. All internal machines are working correctly with other forms of VPN, ie Cisco, Sonic etc (these were tested on other machines, they are not installed on the Vista or Win7 machines). After further testing, this is occurring on all Win7 and Vista machines where they can no longer connect to the client VPN, however all XP machines can still connect fine. This has been tested on three Vista, two Win7 and five XP machines. All machines are on DHCP and tests have been done with both the firewalls turned on and off, as well as with fixed IPs being used. Thanks Travis

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Troubleshoot dropped wireless connections

- by Jack

I was recently hired in the IT department of a small company (~180 users) and one of the issues that people have been complaining about is having their wi-fi connections drop during meetings. The company is using an HP ProCurve Wireless LAN with 10 APs and a controller unit located in the server room. I don't have any experience troubleshooting WLAN in a multi-AP environment, so I'm trying to at least gather information using free or cheap tools. I did a basic site survey using the free version of Ekahau HeatMapper and discovered the following in one of the conference rooms that has been a problem. The program picked up three access points (plus a bunch of others with much lower signals that were out of range): AP 1: SSID: "Unknown SSID" - Signal strength: -48 dBm - -40 dBm. Channel: 2 AP 2: SSID "CompanyMain" - Signal strength: -35 dBm or greater. Channel: 2. Security: WEP (This is the main SSID for the company's WLAN.) AP 3: SSID: "CompanyGuest" - Signal strength: -40 dBm - -35 dBm. Channel: 2. Security: WPA2 (This SSID is the company's "guest" WLAN, which was setup to allow Internet access, but prevent network access.) Is there anything that you see that is clearly a problem from the above? I'm assuming that the unknown SSID might be a big problem, and that it is an AP from a neighboring office that is causing interference. Does that seem likely? Also, regarding channel, should we try changing the channels of our APs to avoid interference with that unknown SSID? (Since everything seems to be on Channel 2?) Should our APs be on different channels? In other words, should the CompanyMain and CompanyGuest APs be on different channels? Finally, any recommendations for free/cheap tools to help me figure this out, and/or a good methodology to follow? Thanks in advance for any help. Jack

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Sendind an internet radio singal from my hifi to a portable

- by Paul

I'm just about to set myself up with a wireless network in my house. This is so that I can intregate an internet radio into my hifi system. What I would love to do is to listen to the radio in another room of the house. I also have a little portable radio/cd player that has a USB port on the front. Is there something I could buy which would allow me to listen to the radio through my portable in another room? I do realize that I could solve this problem by buying some wireless portable speakers, however I just wondered if anybody knew another way i.e. bluetooth or something similar?

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