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  • Portable Socket programming in C/C++ possible?

    - by questions
    I am thinking of creating a multi-platform portable C++ server-client application. Is it even possible while using only standard libraries? If no, what other libraries are there? Are there any improvements in this direction in C++11x? Like for threads, now we have std::threads. To make it more clear.. I want something like boost::thread, which provides multiplatform portable multithreading, for networking. And why C++ doesn't have libraries(standard) for such basic things like networking?

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  • Applet networking patterns

    - by Kristoffersen
    Hi SO. I have an applet that connects to a server, it receives some commands and based on that it haves to draw (or move) different things. Which patterns should I use? I assume that the network connection and applet should run in two different threads? Thanks, Kristoffer

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  • Networking with extremely high latency.

    - by BCS
    Are there any protocols, systems, etc. experimental or otherwise designed for allowing normal (as normal as can be) network operations (E-mail, DNS, HTML, etc.) over very high latency links? I'm thinking of minutes to an hour, or maybe two. Think light speed lag at a solar system scale.

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  • ipad video input

    - by euphoria83
    Is it possible to send video to iPad so that it can either be used for screen sharing or as an extra screen or to watch videos that are being played on another machine, say my mac ? Thanks.

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  • Is there really a need for encryption to have true wireless security? [closed]

    - by Cawas
    I welcome better key-wording here, both on tags and title. I'm trying to conceive a free, open and secure network environment that would work anywhere, from big enterprises to small home networks of just 1 machine. I think since wireless Access Points are the most, if not only, true weak point of a Local Area Network (let's not consider every other security aspect of having internet) there would be basically two points to consider here: Having an open AP for anyone to use the internet through Leaving the whole LAN also open for guests to be able to easily read (only) files on it, and even a place to drop files on Considering these two aspects, once everything is done properly... What's the most secure option between having that, or having just an encrypted password-protected wifi? Of course "both" would seem "more secure". But it shouldn't actually be anything substantial. That's the question, but I think it may need more elaborating on. If you don't think so, please feel free to skip the next (long) part. Elaborating more on the two aspects ... I've always had the feeling using any kind of the so called "wireless security" methods is actually a bad design. I'm talking mostly about encrypting and pass-phrasing (which are actually two different concepts), since I won't even consider hiding SSID and mac filtering. I understand it's a natural way of thinking. With cable networking nobody can access the network unless they have access to the physical cable, so you're "secure" in the physical way. In a way, encrypting is for wireless what building walls is for the cables. And giving pass-phrases would be adding a door with a key. But the cabling without encryption is also insecure. If someone plugin all the data is right there. So, while I can see the use for encrypting data, I don't think it's a security measure in wireless networks. It's wasting resources for too little gain. I believe we should encrypt only sensitive data regardless of wires. That's already done with HTTPS, so I don't really need to encrypt my torrents, for instance. They're torrents, they are meant to be freely shared! As for using passwords, they should be added to the users, always. Not to wifi. For securing files, truly, best solution is backup. Sure all that doesn't happen that often, but I won't consider the most situations where people just don't care. I think there are enough situations where we actually use passwords on our OS users, so let's go with that in mind. I keep promoting the Fonera concept as an instance. It opens up a free wifi port, if you choose so, and anyone can connect to the internet through that, without having any access to your LAN. It also uses a QoS which will never let your bandwidth drop from that public usage. That's security, and it's open. But it's lacking the second aspect. I'll probably be bashed for promoting the non-usage of WPA 2 with AES or whatever, but I wanted to know from more experienced (super) users out there: what do you think?

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  • Virtual Network Interface and NAT disables localhost access for MySQL and Apache

    - by Interarticle
    I'm running an Ubuntu Server 12.04, and recently I configured it to do NAT for my laptop. Since the server has only one NIC, I followed instructions online to create a virtual network device (eth0:0) that has a LAN IP address, then further configured iptables and UFW to allow internet sharing. However, just a few days ago, I discovered that one of the PHP pages hosted on the server failed for no apparent reason. A little digging revealed that the MySQL server started refusing connections from localhost. The same happened with a page (PhpMyAdmin) that was configured to be accessible only from localhost (in Apache2). The error, as shown by $mysql --protocol=tcp -u root -p looks like ERROR 1130 (HY000): Host '<host name of eth0>' is not allowed to connect to this MySQL server However, the funny thing is, I configured the mysql server to allow root access from localhost (only). Moreover, the mysql server listens only on 127.0.0.1:3306, as shown by: sudo netstat -npa | head Active Internet connections (servers and established) Proto Recv-Q Send-Q Local Address Foreign Address State PID/Program name tcp 0 0 127.0.0.1:3306 0.0.0.0:* LISTEN 1029/mysqld which means that the connection could have only come from 127.0.0.1 (Note that MySQL is working because I can still connect to it via unix domain sockets) In effect, it seems that all tcp connections originating from 127.0.0.1 to 127.0.0.1 appear to any local daemon to come from the eth0 IP address. Indeed, apache2 allowed me to access PhpMyAdmin after I added allow <eth0 IP address>. The following are my network configurations (redacted): /etc/hosts: 127.0.0.1 localhost 211.x.x.x <host name of eth0> <server name> #IPv6 Defaults follows .... /etc/network/interfaces: auto lo iface lo inet loopback auto eth0 iface eth0 inet static address 211.x.x.x netmask 255.255.255.0 gateway 211.x.x.x dns-nameservers 8.8.8.8 # dns-* options are implemented by the resolvconf package, if installed dns-search xxxxxxx.com hwaddress ether xx:xx:xx:xx:xx:xx auto eth0:0 iface eth0:0 inet static address 192.168.57.254 netmask 255.255.254.0 broadcast 192.168.57.255 network 192.168.57.0 /etc/ufw/sysctl.conf: #Uncommented the following lines net/ipv4/ip_forward=1 net/ipv6/conf/default/forwarding=1 /etc/default/ufw: DEFAULT_FORWARD_POLICY="ACCEPT" #Changed DROP to ACCEPT /etc/init/internet-sharing.conf (upstart script I wrote), section pre-start script: iptables -A FORWARD -o eth0 -i eth0:0 -s 192.168.57.22 -m conntrack --ctstate NEW -j ACCEPT iptables -A FORWARD -m conntrack --ctstate ESTABLISHED,RELATED -j ACCEPT iptables -A POSTROUTING -t nat -j MASQUERADE Note again that my problem here is that programs cannot access localhost tcp services, from the server itself, and that access is blocked because the services have access control allowing only 127.0.0.1. I have no problem connecting (as in TCP connections) to services via tcp, even if the services listen only on 127.0.0.1. I do NOT want to connect to the services from another computer.

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  • Wget works, Ping doesn't

    - by derty
    There are some anomalies on a Virtuozzo virtualized Debian 4 (I know, I'm gonna upgrade this one asap, but there dependences). We run some Websites on this one. And a view Days ago exmi4 wasnt able to send mails to SOME people. I'll use live.com as exampledomain! So some of this people got mails and some didn't. Some of the mails got stuck in the queue, and after 2 days they went out!! My Nagios never showed problems with the internet connection or disk space Now i wanted to install "dig" to look how he's solving the dns request. And this Debian tells me he doesn't know dig.. Long story made short, Debian is able to download sites with exact IP or even with wget live.com, but it is not able to ping live.com. I'm 99% sure that the networking is right and the routing too! Some examples of my tring below: wget live.com downloads the site ping live.com ping http://www.live.com ping http://live.com returns: ping: unknown host live.com EDIT: i now use heise.de not live.com any more. and i found out i can ping the heise.de server by using it's IP-address. myserver:~# ping 193.99.144.85 PING 193.99.144.85 (193.99.144.85) 56(84) bytes of data. 64 bytes from 193.99.144.85: icmp_seq=1 ttl=248 time=12.7 ms 64 bytes from 193.99.144.85: icmp_seq=2 ttl=248 time=12.6 ms 64 bytes from 193.99.144.85: icmp_seq=3 ttl=248 time=12.9 ms 64 bytes from 193.99.144.85: icmp_seq=4 ttl=248 time=13.1 ms 64 bytes from 193.99.144.85: icmp_seq=5 ttl=248 time=13.1 ms --- 193.99.144.85 ping statistics --- 5 packets transmitted, 5 received, 0% packet loss, time 4001ms rtt min/avg/max/mdev = 12.671/12.924/13.163/0.238 ms EDIT 2: myserver:/etc/apt# dig heise.de ; <<>> DiG 9.3.4-P1.2 <<>> heise.de ;; global options: printcmd ;; Got answer: ;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 40551 ;; flags: qr rd ra; QUERY: 1, ANSWER: 1, AUTHORITY: 5, ADDITIONAL: 3 ;; QUESTION SECTION: ;heise.de. IN A ;; ANSWER SECTION: heise.de. 2266 IN A 193.99.144.80 ;; AUTHORITY SECTION: heise.de. 1622 IN NS ns.pop-hannover.de. heise.de. 1622 IN NS ns.s.plusline.de. heise.de. 1622 IN NS ns.plusline.de. heise.de. 1622 IN NS ns2.pop-hannover.net. heise.de. 1622 IN NS ns.heise.de. ;; ADDITIONAL SECTION: ns.plusline.de. 265 IN A 212.19.48.14 ns.pop-hannover.de. 5113 IN A 193.98.1.200 ns2.pop-hannover.net. 15150 IN A 62.48.67.66 ;; Query time: 2 msec ;; SERVER: 193.200.112.80#53(193.200.112.80) ;; WHEN: Tue Oct 9 13:03:50 2012 ;; MSG SIZE rcvd: 216

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  • Network Restructure Method for Double-NAT network

    - by Adrian
    Due to a series of poor network design decisions (mostly) made many years ago in order to save a few bucks here and there, I have a network that is decidedly sub-optimally architected. I'm looking for suggestions to improve this less-than-pleasant situation. We're a non-profit with a Linux-based IT department and a limited budget. (Note: None of the Windows equipment we have runs does anything that talks to the Internet nor do we have any Windows admins on staff.) Key points: We have a main office and about 12 remote sites that essentially double NAT their subnets with physically-segregated switches. (No VLANing and limited ability to do so with current switches) These locations have a "DMZ" subnet that are NAT'd on an identically assigned 10.0.0/24 subnet at each site. These subnets cannot talk to DMZs at any other location because we don't route them anywhere except between server and adjacent "firewall". Some of these locations have multiple ISP connections (T1, Cable, and/or DSLs) that we manually route using IP Tools in Linux. These firewalls all run on the (10.0.0/24) network and are mostly "pro-sumer" grade firewalls (Linksys, Netgear, etc.) or ISP-provided DSL modems. Connecting these firewalls (via simple unmanaged switches) is one or more servers that must be publically-accessible. Connected to the main office's 10.0.0/24 subnet are servers for email, tele-commuter VPN, remote office VPN server, primary router to the internal 192.168/24 subnets. These have to be access from specific ISP connections based on traffic type and connection source. All our routing is done manually or with OpenVPN route statements Inter-office traffic goes through the OpenVPN service in the main 'Router' server which has it's own NAT'ing involved. Remote sites only have one server installed at each site and cannot afford multiple servers due to budget constraints. These servers are all LTSP servers several 5-20 terminals. The 192.168.2/24 and 192.168.3/24 subnets are mostly but NOT entirely on Cisco 2960 switches that can do VLAN. The remainder are DLink DGS-1248 switches that I am not sure I trust well enough to use with VLANs. There is also some remaining internal concern about VLANs since only the senior networking staff person understands how it works. All regular internet traffic goes through the CentOS 5 router server which in turns NATs the 192.168/24 subnets to the 10.0.0.0/24 subnets according to the manually-configured routing rules that we use to point outbound traffic to the proper internet connection based on '-host' routing statements. I want to simplify this and ready All Of The Things for ESXi virtualization, including these public-facing services. Is there a no- or low-cost solution that would get rid of the Double-NAT and restore a little sanity to this mess so that my future replacement doesn't hunt me down? Basic Diagram for the main office: These are my goals: Public-facing Servers with interfaces on that middle 10.0.0/24 network to be moved in to 192.168.2/24 subnet on ESXi servers. Get rid of the double NAT and get our entire network on one single subnet. My understanding is that this is something we'll need to do under IPv6 anyway, but I think this mess is standing in the way.

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  • Splitting an internet connection between multiple separate subnetworks

    - by pythonian4000
    Problem I have an internet connection that I want to split between four separate networks. My requirements are: I need to be able to monitor the amount of bandwidth and data being used by each network, and notify or control as necessary. The four networks should only be able to connect to the internet, not each other. My parents need to be able to operate it, so it needs a simple, preferably Windows-based GUI. Progress so far Server I have a mini-ITX server with six Gigabit ethernet ports - one for the ethernet internet connection, one for each of the four networks, and one for remote access to the server for administration. Bandwidth control I spent a long time researching solutions here. The majority of the control systems/software I found could control bandwidth usage via QOS, but could not monitor or control the amount of data being used. Eventually I found the SoftPerfect Bandwidth Manager, which has everything I need in terms of monitoring and control - per-interface quota management, usage statistics, a web interface for checking usage, and email notifications when quotas are exceeded. It is also Windows-based and has a simple GUI. Internet sharing This is where I am having issues. I am currently using Windows XP Pro SP2 for the server (yes, I know this is far from ideal, but it's the only spare Windows OS I currently have). I can't use the built-in Internet Connection Sharing for several reasons: The upstream internet router has an IP of 192.168.0.1 which ICS clashes with, and I cannot change the router settings. ICS can only share an internet connection with a single interface, but I have four. I have tried bridging the four network cards, but then the Bandwidth Manager cannot see the four individual interfaces - it only sees the bridge. I have tried setting up Dual DHCP DNS server (and am having issues getting DHCP offers to be received by clients), but that would still require gateway software of some sort, which I have been unable to find. My current attempt is to use OpenVPN, with a server for the internet NIC and a separate client for each of the four networks. My thought is that I could bridge the OpenVPN TAP devices to each NIC, meaning that the Bandwidth Manager would control traffic from the bridge instead of the interface. I have not made much progress here though - I've never used OpenVPN before. Questions Is there a Windows software package that does everything I need? (Unlikely, I know) Is there a Windows software package that will share internet between multiple NICs without bridging? Are either of my about attempts feasible? Would it help to have a newer/server version of Windows? Is there a non-Windows alternative that is easy to use?

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  • DNS lookups failing somewhere between firewall and router

    - by TessellatingHeckler
    we have a setup of ADSL line - Cisco 837 ADSL router - Zyxel ZyWall 35 firewall/NAT - Switch == Intel load balanced NICS in a server. It has been fine for years, suddenly DNS resolution stopped working on the server. No changes that I know of, so I can't work backwards from there. It was configured with the ISP's DNS servers, neither network device does DNS relaying. Wireshark shows the request go out but nothing comes back. The server networking stack seems OK though, because if we query an internal DNS server on a remote site, that works. I can logon to the Cisco, and DNS resolves OK from the command line. I can logon to the ZyWall, and DNS does not resolve from the command line. So the problem seems to be the firewall, patch cable or router, yes? On the router: interface Ethernet0 ip address aaa.bbb.ccc.ddd 255.255.255.ddd ip tcp adjust-mss 1450 hold-queue 100 out On the firewall: DNS server set to 8.8.8.8 (Google's), DNS traffic allowed LAN-WAN. What else should I look for? Update: Following This guide I've got traffic logging on the Cisco. I have also got access to a public DNS server which I can run tcpdump on to see things from the other side. And as per the below comments, I've tested with Dig and see that DNS over TCP works, and over UDP does not. Currently: DNS request from the server using TCP shows up in the firewall log, and in the Cisco log, and in tcpdump on the DNS server, the answer comes back, it works fine. DNS request from the server using UDP shows up in the firewall log, and in the Cisco log, does NOT show in tcpdump on the DNS server, times out. DNS request from the cisco (using UDP) does show up in tcpdump on the DNS server, answer received, works fine. Ping requests from the server and the cisco to the DNS server show up in tcpdump on the DNS server. DNS request from the server using UDP does show up on the firewall. Summary: TCP seems fine throughought. UDP works over the ADSL and to the Cisco, and it works from the server to the Cisco, but it doesn't cross the Cisco properly, it seems. I did see the Cisco showing as connected at 10Mb/full-duplex internally, and the firewall showing as 100Mb/full-duplex externally. I have forced the firewall to 10Mb and rebooted both devices. That seemed to help get UDP traffic (server-firewall-cisco) instead of (server-firewall), but did not fix it. Update: Sanitized Cisco config: version 12.2 no service pad service timestamps debug datetime msec service timestamps log datetime msec service password-encryption ! hostname cisco ! logging queue-limit 100 enable secret 5 {password} enable password 7 {password} ! ip subnet-zero ip domain name example.org ip name-server {nameserver_IP} ! ! ip audit notify log ip audit po max-events 100 no ftp-server write-enable ! interface Ethernet0 ip address {Inside_public_IP} 255.255.255.248 ip tcp adjust-mss 1460 hold-queue 100 out ! interface ATM0 no ip address no atm ilmi-keepalive pvc 0/38 encapsulation aal5mux ppp dialer dialer pool-member 1 ! dsl operating-mode auto ! interface Dialer1 ip unnumbered Ethernet0 encapsulation ppp dialer pool 1 dialer idle-timeout 0 dialer persistent no cdp enable ppp chap hostname {ADSL_Username} ppp chap password 7 {ADSL_Password} ! ip classless ip route 0.0.0.0 0.0.0.0 Dialer1 no ip http server no ip http secure-server ! access-list 23 permit {IP} dialer-list 1 protocol ip permit no cdp run snmp-server enable traps tty ! {con, vty} end

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  • Centos/OVH: public IP on KVM virtual machine

    - by Sébastien
    Since a few days, I'm trying to configure my KVM vm to have a public IP address, without any success. First, I'm on OVH, and you need to know they don't allow networking from different mac addresses. I have so registered a virtual mac address associated with my failover IP Here's my configuration: Guest wanted IP: 46.105.40.x Host IP: 176.31.240.x Host configuration dummy0 interface: ifcfg-dummy0 BOOTPROTO=static IPADDR=10.0.0.1 NETMASK=255.0.0.0 ONBOOT=yes NM_CONTROLLED=no ARP=yes BRIDGE=br0 br0 bridge: ifcfg-br0 DEVICE=br0 TYPE=Bridge DELAY=0 ONBOOT=yes BOOTPROTO=static IPADDR=192.168.1.1 NETMASK=255.255.255.0 PEERDNS=yes NM_CONTROLLED=no ARP=yes Failover ip is redirected to the br0 bridge with ip route add 46.105.40.xxx dev br0 > cat /proc/sys/net/ipv4/ip_forward 1 > cat /proc/sys/net/ipv4/conf/vnet0/proxy_arp 1 > route -n Destination Gateway Genmask Flags Metric Ref Use Iface 0.0.0.0 176.31.240.254 0.0.0.0 UG 0 0 0 eth0 46.105.40.x 0.0.0.0 255.255.255.255 UH 0 0 0 br0 176.31.240.0 0.0.0.0 255.255.255.0 U 0 0 0 eth0 192.168.1.0 0.0.0.0 255.255.255.0 U 0 0 0 br0 Guest configuration: KVM: <interface type='bridge'> <mac address='02:00:00:30:22:05'/> <source bridge='br0'/> <address type='pci' domain='0x0000' bus='0x00' slot='0x06' function='0x0'/> </interface> I've borrowed most of the OVH configuration here (in french, http://guides.ovh.com/BridgeClient) for the guest configuration eth0 interface: ifcfg-eth0 DEVICE="eth0" BOOTPROTO=none HWADDR="02:00:00:30:22:05" NM_CONTROLLED="yes" ONBOOT="yes" TYPE="Ethernet" UUID="e9138469-0d81-4ee6-b5ab-de0d7d17d1c8" USERCTL=no PEERDNS=yes IPADDR=46.105.40.xxx NETMASK=255.255.255.255 GATEWAY=176.31.240.254 ARP=yes For the routes, I have in route-eth0: 176.31.240.254 dev eth0 default via 176.31.240.254 dev eth0 With this configuration, I don't have any access to the internet. The only thing I can do is to ping the public ip of the host, nothing more. My final conclusion is that the route does not work, because, when, on the guest, I run ping 8.8.8.8, I have, on the host: > tcpdump -i vnet0 icmp tcpdump: verbose output suppressed, use -v or -vv for full protocol decode listening on br0, link-type EN10MB (Ethernet), capture size 65535 bytes 13:38:09.009324 IP 46-105-40-xxx.kimsufi.com > google-public-dns-a.google.com: ICMP echo request, id 50183, seq 1, length 64 13:38:09.815344 IP 46-105-40-xxx.kimsufi.com > google-public-dns-a.google.com: ICMP echo request, id 50183, seq 2, length 64 I never get the ping reply, only the request. It seems Guest - Host communication is fine. On eth0: > tcpdump -i eth0 icmp tcpdump: verbose output suppressed, use -v or -vv for full protocol decode listening on eth0, link-type EN10MB (Ethernet), capture size 65535 bytes 13:39:40.240561 IP 46-105-40-xxx.kimsufi.com > google-public-dns-a.google.com: ICMP echo request, id 50439, seq 1, length 64 13:39:40.250161 IP google-public-dns-a.google.com > 46-105-40-xxx.kimsufi.com: ICMP echo reply, id 50439, seq 1, length 64 I have the request and the reply on eth0, but reply is not forwarded to the bridge. I really don't understand why, I though it was the aim of the route to do that! IPtables is disabled on both host and guest. I really hope some of you will be able to help me! Many thanks in advance, Sébastien

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  • Bizarre and very specific Internet connection loss

    - by Synetech
    Yesterday (Friday, September 21, 2012), my Internet connection started acting up. After some testing, I confirmed a very specific and baffling set of symptoms: Internet connection goes away every 25-35 minutes (I did not confirm the exact interval, but it seems to be about 30 mins.) Only some protocols are affected; HTTP*, P2P, etc. stop working; FTP, etc. continue to work When it’s stopped, cannot even ping router or cable-modem IPs or view their firmware pages Domain-names and IPs are irrelevant (for protocols that stop working, neither work, for those that still work, both work) Resetting router fixes it for another 30 minutes Keeping the connection idle or active doesn’t seem to make a difference (nor the bandwidth usage in that period) Connecting directly to cable-modem allows it to work indefinitely Disconnecting the router from the cable-modem works indefinitely (no Internet connection obviously, but can still access router IP and firmware page) Connecting the router to the cable-modem, but putting the modem on standby also works indefinitely Same problem with both a wireless laptop and wired (on any port) desktop (both Windows 7; will try to test Windows XP when possible) Nothing had changed in the days leading up to the issue. No modifications to the networking configuration or the router; there were not even any Windows updates except for an MSSE definition update. Waiting does not fix it, nor does any amount of fiddling with anything; only resetting the router fixes it for 30 minutes (resetting the cable-modem doesn't work either) I tried cleaning the pins in the router’s plugs, but that didn’t help, which was not really a surprise since I was not getting a lost connection error. Obviously my first thought was that the router was having a problem, and this is borne out by some tests. The problem is that when it drops, it is not a full drop since I can still do things like ftp ftp.mcafee.com and such which means that the connection and DNS are still working. Moreover, if it were the router, then why does it stay alive indefinitely when not connected to the cable-modem (i.e., no outside influence)? The problem doesn't seem to be either the cable-modem nor the router, but rather an interaction between the two, like something from the outside (port scan? hacker? ISP?) that is triggering a problem in the router. I see that there have been a couple of vulnerabilities for the DI-524, but those were a while back and should be fixed since I have the last firmware for it. I don’t think it’s my ISP (Rogers) since I have been using the router for several years without problem and can connect indefinitely when bypassing it. But I can’t rule them out since that is one of the only possible things that could have suddenly changed. Does anybody have any ideas of explanations, fixed, or tests? (I note that when I opened the router, I heard a very high-pitched noise from somewhere near the capacitors/ferrite ring which I don’t think I heard the last time I opened it a few years ago, but then if it were that, then why would it affect only a very small, specific set of functions?)

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  • Neighbour table overflow on Linux hosts related to bridging and ipv6

    - by tim
    Note: I already have a workaround for this problem (as described below) so this is only a "want-to-know" question. I have a productive setup with around 50 hosts including blades running xen 4 and equallogics providing iscsi. All xen dom0s are almost plain Debian 5. The setup includes several bridges on every dom0 to support xen bridged networking. In total there are between 5 and 12 bridges on each dom0 servicing one vlan each. None of the hosts has routing enabled. At one point in time we moved one of the machines to a new hardware including a raid controller and so we installed an upstream 3.0.22/x86_64 kernel with xen patches. All other machines run debian xen-dom0-kernel. Since then we noticed on all hosts in the setup the following errors every ~2 minutes: [55888.881994] __ratelimit: 908 callbacks suppressed [55888.882221] Neighbour table overflow. [55888.882476] Neighbour table overflow. [55888.882732] Neighbour table overflow. [55888.883050] Neighbour table overflow. [55888.883307] Neighbour table overflow. [55888.883562] Neighbour table overflow. [55888.883859] Neighbour table overflow. [55888.884118] Neighbour table overflow. [55888.884373] Neighbour table overflow. [55888.884666] Neighbour table overflow. The arp table (arp -n) never showed more than around 20 entries on every machine. We tried the obvious tweaks and raised the /proc/sys/net/ipv4/neigh/default/gc_thresh* values. FInally to 16384 entries but no effect. Not even the interval of ~2 minutes changed which lead me to the conclusion that this is totally unrelated. tcpdump showed no uncommon ipv4 traffic on any interface. The only interesting finding from tcpdump were ipv6 packets bursting in like: 14:33:13.137668 IP6 fe80::216:3eff:fe1d:9d01 > ff02::1:ff1d:9d01: HBH ICMP6, multicast listener reportmax resp delay: 0 addr: ff02::1:ff1d:9d01, length 24 14:33:13.138061 IP6 fe80::216:3eff:fe1d:a8c1 > ff02::1:ff1d:a8c1: HBH ICMP6, multicast listener reportmax resp delay: 0 addr: ff02::1:ff1d:a8c1, length 24 14:33:13.138619 IP6 fe80::216:3eff:fe1d:bf81 > ff02::1:ff1d:bf81: HBH ICMP6, multicast listener reportmax resp delay: 0 addr: ff02::1:ff1d:bf81, length 24 14:33:13.138974 IP6 fe80::216:3eff:fe1d:eb41 > ff02::1:ff1d:eb41: HBH ICMP6, multicast listener reportmax resp delay: 0 addr: ff02::1:ff1d:eb41, length 24 which placed the idea in my mind that the problem maybe related to ipv6, since we have no ipv6 services in this setup. The only other hint was the coincidence of the host upgrade with the beginning of the problems. I powered down the host in question and the errors were gone. Then I subsequently took down the bridges on the host and when i took down (ifconfig down) one particularly bridge: br-vlan2159 Link encap:Ethernet HWaddr 00:26:b9:fb:16:2c inet6 addr: fe80::226:b9ff:fefb:162c/64 Scope:Link UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1 RX packets:120 errors:0 dropped:0 overruns:0 frame:0 TX packets:9 errors:0 dropped:0 overruns:0 carrier:0 collisions:0 txqueuelen:0 RX bytes:5286 (5.1 KiB) TX bytes:726 (726.0 B) eth0.2159 Link encap:Ethernet HWaddr 00:26:b9:fb:16:2c inet6 addr: fe80::226:b9ff:fefb:162c/64 Scope:Link UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1 RX packets:1801 errors:0 dropped:0 overruns:0 frame:0 TX packets:20 errors:0 dropped:0 overruns:0 carrier:0 collisions:0 txqueuelen:0 RX bytes:126228 (123.2 KiB) TX bytes:1464 (1.4 KiB) bridge name bridge id STP enabled interfaces ... br-vlan2158 8000.0026b9fb162c no eth0.2158 br-vlan2159 8000.0026b9fb162c no eth0.2159 The errors went away again. As you can see the bridge holds no ipv4 address and it's only member is eth0.2159 so no traffic should cross it. Bridge and interface .2159 / .2157 / .2158 which are in all aspects identical apart from the vlan they are connected to had no effect when taken down. Now I disabled ipv6 on the entire host via sysctl net.ipv6.conf.all.disable_ipv6 and rebooted. After this even with bridge br-vlan2159 enabled no errors occur. Any ideas are welcome.

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  • Sync my files across multiple computers

    - by EnderMB
    I do a lot of work on my home computer, ranging from programming, writing stored procedures and writing documentation and reporting. A lot of this work is university related and constantly swapping files across several computers is annoying at best. I have a large final-year project coming up and I'm going to be sharing this work amongst home and university and require some kind of online storage that provides version control for my programs, as well as my Word documents, PDF's and saved academic papers. Are there any good solutions for my problem?

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  • Improve file transfer speed between Windows PCs and servers

    - by Geotarget
    I've setup a server which I've connected to multiple PCs in my workplace. Sadly, data transfer speeds are at max 3 MB/sec per connection which works out slow for file transfers, especially when transferring large files. I'm using Windows filesharing and the server is a Windows Server 2008 (2 Ghz CPU, 1 GB RAM) and the client PCs mostly running Windows 7. How can I detect bottlenecks in my network and improve file sharing speed within the network?

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  • Ubuntu Server, 2 Ethernet Devices, Same Gateway - Want to force internet traffic through 1 device (or at least allow it to work!)

    - by Chris Drumgoole
    I have a Ubuntu 10.04 Server with 2 ethernet devices, eth0 and eth1. eth0 has a static IP of 192.168.1.210 eth1 has a static IP if 192.168.1.211 The DHCP server (which also serves as the internet gateway) sits at 192.168.1.1. The issue I have right now is when I have both plugged in, I can connect to both IPs over SSH internally, but I can't connect to the internet from the server. If I unplug one of the devices (e.g. eth1), then it works, no problem. (Also, I get the same result when I run sudo ifconfig eth1 down). Question, how can I configure it so that I can have both devices eth0 and eth1 play nice on the same network, but allow internet access as well? (I am open to either enforcing all inet traffic going through a single device, or through both, I'm flexible). From my google searching, it seems I could have a unique (or not popular) problem, so haven't been able to find a solution. Is this something that people generally don't do? The reason I want to make use of both ethernet devices is because I want to run different local traffic services on on both to split the load, so to speak... Thanks in advance. UPDATE Contents of /etc/network/interfaces: # The loopback network interface auto lo iface lo inet loopback # The primary network interface auto eth0 iface eth0 inet dhcp # The secondary network interface #auto eth1 #iface eth1 inet dhcp (Note: above, I commented out the last 2 lines because I thought that was causing issues... but it didn't solve it) netstat -rn Kernel IP routing table Destination Gateway Genmask Flags MSS Window irtt Iface 192.168.1.0 192.168.1.1 255.255.255.0 UG 0 0 0 eth0 192.168.1.0 0.0.0.0 255.255.255.0 U 0 0 0 eth0 0.0.0.0 192.168.1.1 0.0.0.0 UG 0 0 0 eth0 UPDATE 2 I made a change to the /etc/network/interfaces file as suggested by Kevin. Before I display the file contents and the route table, when I am logged into the server (through SSH), I can not ping an external server, so this is the same issue I was experiencing that led to me posting this question. I ran a /etc/init.d/networking restart after making the file changes. Contents of /etc/network/interfaces: # The loopback network interface auto lo iface lo inet loopback # The primary network interface auto eth0 iface eth0 inet dhcp address 192.168.1.210 netmask 255.255.255.0 gateway 192.168.1.1 # The secondary network interface auto eth1 iface eth1 inet dhcp address 192.168.1.211 netmask 255.255.255.0 ifconfig output eth0 Link encap:Ethernet HWaddr 78:2b:cb:4c:02:7f inet addr:192.168.1.210 Bcast:192.168.1.255 Mask:255.255.255.0 inet6 addr: fe80::7a2b:cbff:fe4c:27f/64 Scope:Link UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1 RX packets:6397 errors:0 dropped:0 overruns:0 frame:0 TX packets:683 errors:0 dropped:0 overruns:0 carrier:0 collisions:0 txqueuelen:1000 RX bytes:538881 (538.8 KB) TX bytes:85597 (85.5 KB) Interrupt:36 Memory:da000000-da012800 eth1 Link encap:Ethernet HWaddr 78:2b:cb:4c:02:80 inet addr:192.168.1.211 Bcast:192.168.1.255 Mask:255.255.255.0 inet6 addr: fe80::7a2b:cbff:fe4c:280/64 Scope:Link UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1 RX packets:5799 errors:0 dropped:0 overruns:0 frame:0 TX packets:8 errors:0 dropped:0 overruns:0 carrier:0 collisions:0 txqueuelen:1000 RX bytes:484436 (484.4 KB) TX bytes:1184 (1.1 KB) Interrupt:48 Memory:dc000000-dc012800 lo Link encap:Local Loopback inet addr:127.0.0.1 Mask:255.0.0.0 inet6 addr: ::1/128 Scope:Host UP LOOPBACK RUNNING MTU:16436 Metric:1 RX packets:635 errors:0 dropped:0 overruns:0 frame:0 TX packets:635 errors:0 dropped:0 overruns:0 carrier:0 collisions:0 txqueuelen:0 RX bytes:38154 (38.1 KB) TX bytes:38154 (38.1 KB) netstat -rn Kernel IP routing table Destination Gateway Genmask Flags MSS Window irtt Iface 192.168.1.0 0.0.0.0 255.255.255.0 U 0 0 0 eth0 192.168.1.0 0.0.0.0 255.255.255.0 U 0 0 0 eth1 0.0.0.0 192.168.1.1 0.0.0.0 UG 0 0 0 eth1 0.0.0.0 192.168.1.1 0.0.0.0 UG 0 0 0 eth0

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  • Unable to share a folder between Windows 7 and Ubuntu (running in VMWare)

    - by darthvader
    I have installed vmware toolbox in ubuntu (guest OS). I tried to share a location from the settings of the virtual machine. But when I click Ok, the following error in thrown in the host (Win 7) OS. "Unable to update run-time folder sharing status: Unknown error." The location is not showing up in /mnt/ What could be the reason? P.S I have vmhgfs process running in my Ubuntu VM. I was following this method.

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  • Is it necessary to share every underlying folder in a Dropbox shared folder?

    - by ErnstvdS
    I have one Dropbox (I suppose) shared between my business account / PC and my wife's account / PC running Windows XP and a laptop with Windows 7. I created a folder and shared this one with both (or three) accounts. I created an underlying folder (no need to share, says the help) but it is not visible on the other PCs, so I've shared it to both accounts. Is this sharing necessary for every simple new folder?

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  • Using Dropbox as a cloud based file share - does everyone need an upgraded account?

    - by aSkywalker
    We have a file share in our small office (3-5 users). We now have the need for the files to be accessible outside of the office. I like the idea of dropbox - we have been using it for small remote sharing. If we buy the upgrade account, and move 30 to 70 gigs of files to it, will every user have to have the pro account? I have submitted this question to dropbox - but thought that the advice of users here would also be valuable

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  • How to troubleshoot port forwarding on Windows 7 (64 Bit) with ICS enabled?

    - by LearnCocos2D
    I want to forward some ports (1666 for perforce, 8081 for Hudson) on my Internet Gateway machine. This machine is running Windows 7 (64 Bit, legal, user-account) and connected to the Internet via cable modem (it's not a router). The Windows machine is sharing its Internet Connection via ICS and that works fine on all connected computers. I can access the services via the gateway's public IP (95.x.x.x) on the given ports if they are running on the gateway machine itself. I've added the ports and destination IP address (192.168.0.18) in the Internet network adapter's Advanced Settings dialog (Sharing tab). That's the same dialog where you have a list of preconfigured services like HTTP, FTP and other incoming services. When I do that I can't connect to the services anymore. For some reason port forwarding isn't working. I have uninstalled Bitdefender because I wanted to check if the Firewall interferes. I've also disabled the Windows Firewall and Defender to no avail. I tried a freeware tool that helps to setup port forwarding but that didn't work either. The target machine is a Mac OS X computer whose Firewall is disabled. The IP is static. I can successfully connect to the services using the local IP address (192.168.0.18) from two different machines, including the gateway computer. So internally and externally it seems to me that the ports are open and not blocked, and the issue is with port forwarding itself. From what I understand it should be enough to add an entry to the Advanced Settings dialog to enable port forwarding when there are no firewalls interfering. How can I troubleshoot why port forwarding isn't working for me? What steps should I follow to alleviate the issue? PS: I gladly accept command line solutions. Other things I've tried: adding an Inbound Rule to Windows Firewall for the 1666, 8081 ports trying with Windows Firewall enabled and disabled disabling/enabling the network adapter double-checked that the IP addresses are correct mapping a different incoming port to the service's actual port followed or checked the misc tips in this article What I haven't dared trying yet (let me know if it's worth a shot): disable/enable ICS remove all network adapters (via Control Panel), then re-install and re-configure them

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  • Unable to share a folder between Windows 7 and Ubuntu (running in VMWare)

    - by iJeeves
    I have installed vmware toolbox in ubuntu (guest OS). I tried to share a location from the settings of the virtual machine. But when I click Ok, the following error in thrown in the host (Win 7) OS. "Unable to update run-time folder sharing status: Unknown error." The location is not showing up in /mnt/ What could be the reason? P.S I have vmhgfs process running in my Ubuntu VM. I was following this method.

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  • Can a windows virus downloaded in linux be transferred to windows?

    - by user219048
    I know that linux is mostly safe from viruses, however: if you do download a windows virus (i.e., through a drive-by download), will it just sit there on your computer, and take up space? Is it unable to infect files because of the different operating system? If you transfer files between computers (by using a usb flash drive or through online file sharing), is there any risk that the virus could be transferred to windows and activate?

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