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  • Just one client bound to address and port: does it make a difference broadcast versus unicast in terms of overhead?

    - by chrisapotek
    Scenario: I am implementing failed over for a network node, so my idea is to make the master node listens on a broadcast ip address and port. If the master node fails, another failover node will start listening on this broadcast address (and port) and take over. Question: My concern is that I will be using a broadcast IP address just for a single node: the master. The failover node only binds if the master fails, in other words, almost never. In terms of network/traffic overhead, is it bad to talk to a single node through a broadcast address or the network somehow is smart enough to know that nobody else is listening to this broadcast address and kind of treat it as a unicast in terms of overhead? My concern is that I will be flooding my network with packets from this broadcast address even thought I am just really talking to a single node (the master). But I can't use unicast because the failover node has to be able to pick up the master stream quickly and transparently in case it fails.

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  • Virtual Machine Network Architecture, Isolating Public and Private Networks

    - by Mark
    I'm looking for some insight into best practices for network traffic isolation within a virtual environment, specifically under VMWARE ESXi. Currently I have (in testing) 1 hardware server running ESXi but i expect to expand this to multiple pieces of hardware. The current setup is as follows: 1 pfsense VM, this VM accepts all outside (WAN/internet) traffic and performs firewall/port forwarding/NAT functionality. I have multiple public IP addresses sent to the this VM that are used for access to individual servers (via per incoming IP port forwarding rules). This VM is attached to the private (virtual) network that all other VMs are on. It also manages a VPN link into the private network with some access restrictions. This isn't the perimeter firewall but rather the firewall for this virtual pool only. I have 3 VMs that communicate with each other, as well as have some public access requirements: 1 LAMP server running an eCommerce site, public internet accessible 1 accounting server, access via windows server 2008 RDS services for remote access by users 1 inventory/warehouse management server, VPN to client terminals in warehouses These servers constantly talk with each other for data synchronization. Currently all the servers are on the same subnet/virtual network and connected to the internet through the pfsense VM. The pfsense firewall uses port forwarding and NAT to allow outside access to the servers for services and for server access to the internet. My main question is this: Is there a security benefit to adding a second virtual network adapter to each server and controlling traffic such that all server to server communication is on one separate virtual network, while any access to the outside world is routed through the other network adapter, through the firewall, and on the the internet. This is the type of architecture i would use if these were all physical servers, but i'm unsure if the networks being virtual changes the way i should approach locking down this system. Thank you for any thoughts or direction to any appropriate literature.

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  • Kernel Log "TCP: Treason uncloaked!"

    - by hurikhan77
    On one linux server (Gentoo hardened), we are experiencing bursts of the following messages in dmesg from time to time: TCP: Treason uncloaked! Peer xx.xx.xxx.xxx:65039/80 shrinks window 4094157295:4094160199. Repaired. Is there anything we should take care of or is this normal? Update: Maybe related, we are using net.ipv4.tcp_congestion_control = cubic. Kernel version is 2.6.28 with Gentoo hardening patches.

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  • With CentOS 6 and LXC, "ifconfig" is unable to see network interface (but busybox "ifconfig" works fine)

    - by larsks
    I've just started working with LXC under CentOS 6 (via the libvirt adapter). If I create an LXC container, I'm unable to see any network interfaces when using the native system tools: # ifconfig -a # The behavior is very odd; specifying an interface by names yields neither the expected output nor an error message. This is true even for clearly invalid interface names, like this: # ifconfig foo # The ip command exhibits the same behavior. On the other hand, if I use "ifconfig" provided by busybox, everything works as expected: # busybox ifconfig -a eth0 Link encap:Ethernet HWaddr 52:54:00:E0:12:C8 inet6 addr: fe80::5054:ff:fee0:12c8/64 Scope:Link UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1 RX packets:268 errors:0 dropped:0 overruns:0 frame:0 TX packets:6 errors:0 dropped:0 overruns:0 carrier:0 collisions:0 txqueuelen:1000 RX bytes:17814 (17.3 KiB) TX bytes:552 (552.0 B) 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:0 errors:0 dropped:0 overruns:0 frame:0 TX packets:0 errors:0 dropped:0 overruns:0 carrier:0 collisions:0 txqueuelen:0 RX bytes:0 (0.0 B) TX bytes:0 (0.0 B) So...what does busybox know that the native tools don't? The libvirt config for this environment is pretty standard; the network definition looks like this: <interface type='network'> <mac address='52:54:00:e0:12:c8'/> <source network='default'/> <target dev='veth0'/> </interface> The full configuration is here if you think it might help. I'm running: lxc-0.7.2-2.el6.x86_64 kernel-2.6.32-71.29.1.el6.x86_64 EDIT Weirder and weirder...it's a display issue, not a functionality issue. I can see the output of ifconfig if I pipe it into anything, so for example: # ifconfig eth0 | cat eth0 Link encap:Ethernet HWaddr 52:54:00:E0:12:C8 inet addr:192.168.10.10 Bcast:192.168.10.255 Mask:255.255.255.0 inet6 addr: fe80::5054:ff:fee0:12c8/64 Scope:Link UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1 RX packets:573 errors:0 dropped:0 overruns:0 frame:0 TX packets:6 errors:0 dropped:0 overruns:0 carrier:0 collisions:0 txqueuelen:1000 RX bytes:37914 (37.0 KiB) TX bytes:552 (552.0 b) And in fact even when not piping the output, strace shows that ifconfig is in fact writing the output to file descriptor 1 (aka stdout), so it's not clear why no output is actually showing up. This could be either an LXC or a virsh issue, I guess.

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  • High load average due to high system cpu load (%sys)

    - by Nick
    We have server with high traffic website. Recently we moved from 2 x 4 core server (8 cores in /proc/cpuinfo), 32 GB RAM, running CentOS 5.x, to 2 x 4 core server (16 cores in /proc/cpuinfo), 32 GB RAM, running CentOS 6.3 Server running nginx as a proxy, mysql server and sphinx-search. Traffic is high, but mysql and sphinx-search databases are relatively small, and usually everything works blazing fast. Today server experienced load average of 100++. Looking at top and sar, we noticed that (%sys) is very high - 50 to 70%. Disk utilization was less 1%. We tried to reboot, but problem existed after the reboot. At any moment server had at least 3-4 GB free RAM. Only message shown by dmesg was "possible SYN flooding on port 80. Sending cookies.". Here is snippet of sar 11:00:01 CPU %user %nice %system %iowait %steal %idle 11:10:01 all 21.60 0.00 66.38 0.03 0.00 11.99 We know that this is traffic issue, but we do not know how to proceed future and where to check for solution. Is there a way we can find where exactly those "66.38%" are used. Any suggestions would be appreciated.

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  • Does an unmanaged 4/8-port GBit Ethernet switch with a GBIC port exist?

    - by Aaron Digulla
    I'm looking for a simple unmanaged switch with 4-8 GBit Ethernet ports and a fiber port (either as a GBIC slot or pre-installed with a 1000BASE-SX port). Does something like that exist? [EDIT] I want to connect to places in my home without drilling large holes though the floors. Therefore, I'm looking for a cheap way to connect two GBit switches via fiber. I tried with a media converter (GBit <- multimode fiber) but that costs about 50% throughput. So I was hoping that there is a cheap, small GBit switch which has a GBIC slot). All I found so far are very expensive managed switches with 12 or 24 ports for industry use.

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  • Using a MiFi via WDS

    - by Joril
    I have a Huawei R201 MiFi connected to the internet, and I'd like to use its internet connection even from devices that don't have WiFi, so I grabbed a wireless router I had lying around and configured WDS so that it'd connect to the MiFi, and this is working nicely (I can ping the MiFi from the router web interface). The next step was connecting my PC to the router via ethernet cable, but now I'm stuck... The PC can ping the router, but not the MiFi (they're all on the same subnet). Since the router can ping the MiFi, I guess this is some kind of routing issue? Should I get a more "flexible" router, such as one with DD-WRT maybe? Is what I'm trying to do even possible? (For the record the PC is running Lubuntu 11.10)

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  • How to achieve reliable Gigabit Ethernet Link with my Acer Aspire Revo R3610?

    - by The Operator
    I want to stream HD movies over my wired Gigabit LAN from my PC to my Acer Aspire Revo R3610. It's connected with a 3ft Cat5e patch cable to my Netgear GS605v2 Switch. The PC acting as File Server is connected at 1Gbps to the Switch. Network driver options are set to defaults, including automatic speed/duplex negotiation on both machines. The Revo will not connect to my Network Switch at 1Gbps - the OS reports that it reverts to 100Mbps either shortly after connection or immediately upon connection. Through a process of elimination (trying different drivers, patch cables, ports on the switch, and other 1Gbps-capable devices connected to the Network switch which successfully achieve 1Gbps links and performance) I have drawn the conclusion there is either a Hardware or Software (Driver) issue with the Revo itself. I have performed tests using Windows 7 and Ubuntu 9.10. Can anyone offer insight on Gigabit Ethernet with the Revo?

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  • dig lookup different from system lookup

    - by simao
    Hello, I am running dd-wrt and I configured it's dns server to resolve a few hosts inside my network. When I use dig to lookup these hosts, they are resolved OK, but when I try to ping those hosts I always receive an unknown host error message. For example: obe:~ simao$ dig dd-wrt ; <<>> DiG 9.6.0-APPLE-P2 <<>> dd-wrt ;; global options: +cmd ;; Got answer: ;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 44026 ;; flags: qr aa rd ra; QUERY: 1, ANSWER: 1, AUTHORITY: 0, ADDITIONAL: 0 ;; QUESTION SECTION: ;dd-wrt. IN A ;; ANSWER SECTION: dd-wrt. 0 IN A 192.168.1.1 But then: obe:~ simao$ ping dd-wrt ping: cannot resolve dd-wrt: Unknown host Any ideas? Thanks.

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  • How to forward UDP and TCP traffic from one IP to another

    - by Rishabh Agnihotri
    Well i have a server with two LAN Card Installed.I have a server in U.S and one in India.I have created a GRE tunnel to route all traffic from U.S Server to my Indian Server.My Traffic has UDP,TCP,HTTP,etc Traffic.Now i have two LAN Card on my Indian Server.Well i have configured two IPs on the system for some of my needs on the system.One is a /30 and another is a /24.Well now i want the /30 IP to talk to my /24 IP.Lets take a e.g the IPs are 180.151.130.34 - /30 and 103.243.19.254 -/24 I want to forward all the TCP,UDP,HTTP,etc like traffic coming to 180.151.130.34 to 103.243.19.254.In the sense i want to make them talk to each other in a way if a TCP/UDP Packet comes to 180.151.130.34 it should be forwarded to 103.243.19.254 and then that packet is sent back by 103.243.19.254 to 180.151.130.34.I am not able to configure this part.Can anyone tell me step by step how to do so? Well i forgot to specify i am using Windows Server 2008. Any help would be greatly appreciated.Thanks in advance.

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  • Suggestions for wireless adapter

    - by Michael Kniskern
    I recently purchased a desktop computer and it did not come with a wireless network card. I am currently using the Belkin Wireless G USB Adapter and it is a very sub par product. It has very slow response times and download speeds with just basic browsing and downloads podcasts through iTunes. Does anyone have a better suggestion for a wireless adapter? Should I go with another USB adapter or one that connects directly into the motherboard? I am current using Windows Vista 64 bit Home Premium.

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  • debian gateway using iptables

    - by meijuh
    I am having problems setting up a debian gateway server. My goal: Having eth1 the WAN interface. Having eth0 the LAN interface. Allow both ports 22 (SSH) and 80 (HTTP) accessed from the outside world on the gateway (SSH and HTTP run on this server). What I did was the following: Create a file /etc/iptables.rules with contents: /etc/iptables.rules: *nat -A POSTROUTING -o eth1 -j MASQUERADE COMMIT *filter -A INPUT -i lo -j ACCEPT -A INPUT -m state --state RELATED,ESTABLISHED -j ACCEPT -A INPUT -i eth1 -p tcp -m tcp --dport 22 -j ACCEPT -A INPUT -i eth1 -p tcp -m tcp --dport 80 -j ACCEPT -A INPUT -i eth1 -j DROP COMMIT edit /etc/network/interfaces as follows: /etc/network/interfaces: # The loopback network interface auto lo iface lo inet loopback pre-up iptables-restore < /etc/iptables.rules auto eth0 allow-hotplug eth0 iface eth0 inet dhcp #auto eth1 #allow-hotplug eth1 #iface eth1 inet dhcp allow-hotplug eth1 iface eth1 inet static address 217.119.224.51 netmask 255.255.255.248 gateway 217.119.224.49 dns-nameservers 217.119.226.67 217.119.226.68 Uncomment the rule net.ipv4.ip_forward=1 in /etc/sysctl.conf to allow packet forwarding. The static settings for eth1 such as the ip address I got from my router (which I want to replace); I simply copied these. I have a (windows) DNS + DHCP server on ip address 10.180.1.10, which assigns ip address 10.180.1.44 to eth0. What this server does is not really interesting it only maps domain names on our local network and assigns one static ip to the gateway. What works: on the gateway itself I can ping 8.8.8.8 and google.nl. So that is okey. What does not work: (1) Every machine connected to eth0 (indirectly via a switch) can not ping an ip or a domain. So I guess the gateway can not be found. (2) Also when I configure my linux machine (a laptop) to use a static ip 10.180.1.41, a mask and a gateway (10.180.1.44) I can not ping an ip or domain either. This means that maybe my iptables is incorrect of not loaded correctly. Or I maybe have to configure my DNS/DHCP on my windows machine. I have not reset the windows machine net, restart the DNS/DHCP services, should I do this? I did not install dnsmasq as desribed here: http://blog.noviantech.com/2010/12/22/debian-router-gateway-in-15-minutes/. I don't think this is necessary?

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  • CentOS/Apache killing connections

    - by fin1te
    Getting a really strange error. Basically, whenever I browse to my server (http://[ip_address] or http://[hostname]), it doesn't load, and my active SSH connection drops out. I installed CentOS 5.5, and then httpd and PHP 5.3. No other applications where installed, so I can't imagine it's something else causing it. I also reinstalled CentOS 5.5 again, completely fresh, the only thing I did to it was yum install httpd, and it still caused this issue. I've changed nothing in the config or anything else. Driving me mad, has anyone heard of this? It's really frustrating since everytime I attempt to debug this issue, I get kicked off SSH and have to log back in. Theres nothing in the Apache error logs, and nothing in the access log recording my attempt. Also, the result from uname - Linux [hostname] 2.6.35.4-rscloud #8 SMP Mon Sep 20 15:54:33 UTC 2010 x86_64 x86_64 x86_64 GNU/Linux Thank you

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  • racoon-tool doesn't generate full racoon.conf file in /var/lib/racoon/racoon.conf

    - by robthewolf
    I am using ipsec-tools/racoon to create my VPN. I am using racoon-tool to configure racoon.conf but when I run racoon-tool reload it only generates the first section - Global items. When I run racoon-tool I get: # racoon-tool reload Loading SAD and SPD... SAD and SPD loaded. Configuring racoon...done. This is the entire file /var/lib/racoon/racoon.conf # # Racoon configuration for Samuel # Generated on Wed Jan 5 21:31:49 2011 by racoon-tool # # # Global items # path pre_shared_key "/etc/racoon/psk.txt"; path certificate "/etc/racoon/certs"; log debug; I cannot find anywhere a solution as to why this is happening. Please help

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  • Network monitoring solution

    - by Hellfrost
    Hello Serverfault ! I have a big distributed system I need to monitor. Background: My system is comprised of two servers, concentrating and controlling the system. Each server is connected to a set of devices (some custom kind of RF controllers, doesnt matter to my question), each device connects to a network switch, and eventually all devices talk to the servers, the protocol between the servers and the devices is UDP, usually the packets are very small, but there are really a LOT of packets. the network is also somewhat complex, and is deployed on a large area physically. i'll have 150-300 of these devices, each generating up to 100+ packets per second, and several network switches, perhaps on 2 different subnets. Question I'm looking for some solution that will allow me to monitor all this mess, how many packets are sent, where, how do they move through the network, bandwidth utilization, throughput, stuff like that. what would you recommend to achieve this? BTW Playing nice with windows is a requirement.

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  • dhcpd pool exhaustion - What's the result?

    - by jarmund
    I have a DHCP server that serves leases to several houndred, maybe up to a thousand, different clients on an average day. The pool consists of 242 IPs, and due to the highly dynamic nature of the network, it's enough 99% of the time (most devices are gone from the network in a few minutes), despite having a lease time of 3600. Now, imagine if more clients than that connect to the network during an hour. The sollution is obvious: Decrease lease time, or increase the DHCP pool, however, what i would like to know: What happens when dhcpd has exhausted the pool? Are new DHCP requests simply ignored?

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  • Always use one slow connection in preference of a "faster" one

    - by billc.cn
    In Windows, there's this automatic metric thing where the metric is selected according to the declared speed of the link. I now have a gigabit LAN routed to a 2MB DSL service and a HSDPA mobile broadband connection. The former is always chosen for Internet packets even though the latter is actually faster. I tried setting the mobile broadband's interface metric to 1 and raising its priority in the advanced settings of the adapter settings, but this does not seem to affect the metric of the default route. The default route to the Ethernet interface always have a lower metric than the mobile broadband interface. Am I missing something here?

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  • How do I register a service with Bonjour?

    - by Roman
    I am trying to start to use Bonjour. Here I found a manual how to register a service with Bonjour. The following is written there: The network services architecture in Bonjour includes an easy-to-use mechanism for publishing, discovering, and using IP-based services. Well let's see how to register a service. In the very beginning it is written: To publish a service, an application or device must register the service with a Multicast DNS responder But how?!?! First of all I do not know what is the Multicast DNS responder. Second, it is not written how do I do it. Where and what should I type? Should I use command line? Should I use some programming languages? What exactly should I type... Is there an easy way to start to use Bonjour? Well, it was emphasized several times how easy it should be to use it. But I cannot start to use it for several day. So, can anybody, pleas, help me with that?

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  • How do I configure tinydns (with fefe's IPv6 patch) to listen on IPv6 address?

    - by Christian Hudon
    I'm setting up my network to support IPv6. I have static IPv6 addresses assigned to each interface of my router, and radvd advertising different prefixes on each interface. The next step would be to get my dnscache (from djbdns) working on IPv6. Said dnscache has fefe's IPv6 patch applied, so I assume it should work with IPv6. However, I can't find any documentation online on how to make the patched dnscache listen on IPv6. How do I configure tinydns and dnscache to listen on IPv6 too?

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  • Which ports to open on host firewall so that network printing and scanning works?

    - by George Pligor
    I have a multi-functional machine which is both a laser printer and a scanner (Samsung SC-4705ND) I am not able to make the scanner work with the (software) firewall installed in my computer turned on. Operating system is ubuntu 12.04 with regular firewall. if firewall is turned off then everything works as expected I run nmap to discover open services on the samsung machine and I opened all these ports: 80, 427, 515, 631, 5200, 9100, 10001 but with not luck.. How should I configure firewall?

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  • mystery Internet traffic to port 445

    - by Ben Collver
    Recently, I noticed traffic from the office network to TCP port 445 on the Internet [a]. Below are the Linux firewall log entries to Facebook's network [b] and Google's network [c]. I would like to identify the source of this traffic. My first guess is that Facebook and Google might be using multiple TCP ports for SSL load balancing. However, I could not confirm this based on the web proxy logs. What else might it be? [a] http://support.microsoft.com/kb/204279 [b] Sep 4 08:30:03 firewall01 kernel: IN=eth0 OUT=eth2 SRC=10.0.0.131 DST=69.171.237.34 LEN=52 TOS=0x00 PREC=0x00 TTL=127 ID=14287 DF PROTO=TCP SPT=51711 DPT=445 WINDOW=8192 RES=0x00 SYN URGP=0 [c] Aug 28 06:02:41 firewall01 kernel: IN=eth0 OUT=eth2 SRC=10.0.0.115 DST=173.194.33.47 LEN=52 TOS=0x00 PREC=0x00 TTL=127 ID=4558 DF PROTO=TCP SPT=49294 DPT=445 WINDOW=8192 RES=0x00 SYN URGP=0

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  • ASA and cisco vs NSA sonic firewall

    - by Lbaker101
    Currently I’m trying to structure our network to fully support and be redundant with BGP/Multi homing. Our current company size is 40 employees but the major part of that is our Development department. We are a software company and continued connection to the internet is a requirement as 90% of work stops when the net goes down. The only thing hosted on site (that needs to remain up) is our exchange server. Right now i'm faced with 2 different directions and was wondering if I could get your opinions on this. We will have 2 ISPs that are both 20meg up/down and dedicated fiber (so 40megs combined). This is handed off as an Ethernet cable into our server room. ISP#1 first digital ISP#2 CenturyLink we currently have 2x ASA5505s but the 2nd one is not in use. It was there to be a failover and it just needs the security+ license to be matched with the primary device. But this depends on the network structure. I have been looking into the hardware that would be required to be fully redundant and I found that we will either of the following. 2x Cisco 2921+ series routers with failover licenses. They will go in front of the ASAs and either connects in a failover state or 1 ISP into each of the 2921 series routers and then 1 line into each of the ASAs (thus all 4 hardware components will be used actively). So 2x Cisco 2921+ series routers 2x Cisco ASA5505 firewalls The other route 2x SonicWalls NSA2400MX series. 1 primary and the secondary will be in a failover state. This will remove the ASAs from the network and be about 2k cheaper than the cisco route. This also brings down the points of failure because it’s just the 2x sonicwalls It will also allow us to scale all the way up to 200-400 users (depending on their configuration). This also makes so the Sonic walls. So the real question is with the added functionality ect of the sonicwall is there a point in paying so much more to stay the cisco route? Thanks!

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  • How to connect cable internet on ubuntu

    - by NAVEED
    I was using my cable internet on windows and it was working. Now I moved to ubuntu for development work. But I am unable to connect this internet on ubuntu. I called their technical support and they ask me to install PTPPN (I have forgot the exact name) and then provide our server name, your username and passowrd. I download that software PTPPN(whatever) by using a debian file but I did not find it after installation. I tried to contact to technical support again but unable to connect. Can someone please tell the exact name of that software and how to install and then connect to internet on ubuntu? I have only the following information for now: Install "PTPN" on ubuntu. (forgot exact name of this package) servername: blue.connect.net.pk username: myusername password: mypassword Thanks

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  • Windows 7 - system error 5 problem

    - by ianhobson
    My wife has just had a new computer for Christmas (with an upgrade from VISTA to Windows 7), and has joined the home network. We are using a mix of WindowsXP and Ubuntu boxes linked via a switch. We are all in the same workgroup. (No domain). Internet access, DHCP, and DNS server is an SME server that thinks it is domain controller (although we are not using a domain). I need to run a script to back up my wife's machine (venus). In the past the script creates a share on a machine with lots of space (leda), and then executes the line. PSEXEC \\venus -u admin -p adminpassword -c -f d:\Progs\snapshot.exe C: \\leda\Venus\C-drive.SNA With the wife's old XP machine, this would run the sysinternals utility, copy shapshot,exe to her machine and run it, which would then back up her C: drive to the share on leda. I cannot get this to work with Windows 7, nor can I link through to the C$ share on her machine. This gives me a permissions error (system error 5). The admin account is a full admin account. And yes - I do know the password. The ordinary shares on her machine work fine! I guess I'm missing something that Microsoft have built into Windows 7 - but what? The machine is running Windows 7 business, with windows firewall, AVG anti virus, and all the crap-ware you get with a new PC removed. Thanks

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