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• Windows mounted network drives slow after upgrading switch

  - by Kver

  On our small business network our old 10/100 consumer grade switch gave up the ghost, and we replaced it with a proper business-grade gigabyte switch. After wiring it in our Linux and Mac users immediately got back to working off of network drives; But 2 of our 3 Windows 7 PCs have suddenly experienced a tremendous slowdown with mapped network drives; Windows will become stuck "discovering" a folder causing applications to freeze when trying to open files. It will instantly display and browse files, but the moment you try to open one the bug hits. To remedy this we have our users copying files to the desktop, but it can take a few minutes while windows is stuck "calculating" the time it will take to copy. These aren't big files, mostly excel sheets less than 500KB - these operations are instant on Linux and Mac. (The third Windows machine is having no issues) I've tried remapping the drives, mapping to different drive letters, rebooting, etc. I'm at a loss, because switches are mostly transparent, and it's only after the switch was replaced that the Windows PCs started acting up. What black-magic voodoo am I missing to make Windows work? Thank you.

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• Service redirection on same network

  - by Unode

  I have a network on which I run multiple servers each dedicated to a given service. Because most services run on distinct ports I'm currently looking for a way of unifying "all" services into a single "proxy" machine. The idea is to abstract which machine is being accessed but still allow direct connection if needed/requested. This "proxy" machine has only one network interface which is part of the same network as all the other service providing machines. I've looked into Routing and NAT but I've so far failed to figure out how to make it work. I tried to achieve this using shorewall but couldn't find clear examples. However I'm not entirely sure this is the best/simplest strategy. With that said, what would be the best way of achieving this result? Example case: Proxy IP - Listening port - Send requests to 192.168.0.50 80 192.168.0.1:80 " 22 192.168.0.2:2222 " 3306 192.168.0.3:3000 " 5432 192.168.0.4:5432 " 5222 192.168.0.5:5222 PS: I'm not concerned with the single-point-of-failure nature of the proxy. Thanks

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• Having an issue trying to get Gigabit speed across my network (Ubuntu Server)

  - by user94217

  I've just started looking into the network speeds at my office, the entire network is setup to be "Gigabit". This includes Gb switches, Gb Network cards and Cat 5e cabling. I'm not expecting the full speed, I just want more than ~90 Mb/s. I've been running some tests with iperf the linux tools and checking the hardware with ethtool. I have 3 servers and when doing my checks/test I discovered that the two backup servers can access each other at around 450 Mb/s but when using either one of them to connect and test the main server, I only get the 90Mb/s even though ethtool shows the networking card running at 1000/Full. The only difference between all the server/networking cards is the "Port" which ethtool shows. On the two backup servers the "Port" is shown as MII yet on the other it's shown as "Twisted Pair". When using ethtool -s to manually set the "Port" to MII on the main server, it looses all connectivity and does not show "Speed" or "Duplex". Anyway, Am i doing something wrong? Is there a specific reason my main server cannot use Gb when there appears to be no difference except the "Port"?

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• VirtualBox bridged network not working as expected

  - by iby chenko

  I am having hard time getting Bridged network to work with VirtualBox. Idea is to have host as well as one or more guests on same LAN. Using NAT (default) I do get access to internet and any node on the LAN when working from one of the VM guests. However, no LAN node including host can access (or ping) guest in VM. I need to be able to use any guest as if it was a physical computer on the network (need to be accessed by any machine on LAN). According to my understanding of the VirtualBox documentation, this should be Bridged mode. I think I set it correctly, well, actually there is not much to it: 1. select Bridged mode in VM network setup 2. select physical NIC of the host to connect bridge to 3. start VM When I do this, each VM does get new IP address that corresponds to LAN settings : 192.168.1.100 192.168.1.102 192.168.1.103 etc. where host is 192.168.1.80 / 255.255.255.0 (IP addresses above 100 are served by DHCP server). This seem to be correct based on what I know about ethernet. From VM I can ping other nodes like 192.168.1.50 etc. and I still get ethernet access. So far so good... But I STILL cannot ping any of the other VMs (running ones of course). I cannot ping them from other VMs, from host or from other nodes on the LAN. Aside from fact that IP addresses handed to guests are now local, this still acts same as NAT. What is going on? What am I missing? Regards, I

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• how to build network across buildings ?

  - by Omie

  Hi ! I need some help in building a network between hundreds of computers spread across multiple buildings of my college. Yes, I'll be doing this as a part of my college project. Please see this image, it will give you enough idea of what I'm trying to achieve. http://i.imgur.com/rOohx.png All the computers in all buildings should be able to connect server. Once network is up, there will be a set of services over intranet and network use will be moderate. well, say there will be an email server and a http server. My point is, I cannot afford much of performance loss. It feels easy to connect computers inside 1 building to each other, however, I'm clueless as to how to connect all of them to server. I mean, just 1 cable won't be enough to connect 1 building to server, right ? How should I go with it ? I am not expecting detailed configuration. Just heads up will do :) Thanks

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• Protocol (or service publish/discovery) to detect devices in network

  - by Gobliins

  we connect some embedded devices in a network. What i am looking for now, is a way to find the devices IP and identify them. We work with Windows PC´s and i am about to write a C# tool that should do this. I thought about send a udp broadcast and in the ack i.e. is the device´s ip, which would mean the device needs a daemon runnig to assign an ip itself. Running a service (like a printer) on the device, and on the PC just lookup for the service. I read about some things like apipa, zeroconf, ipv4 local link, bonjour, dns-sd, mdns, bonjour; They can automatically assign ip´s and publish services in a network. My Question is, can someone recommend me what would be good for my task? -The protocol or Service should be low on ressource (memory/cpu usage) use. -Are there some standard protocolls to use? -Is DNS a good idea or would it be to ressource consumpting just for finding a device´s IP? -Should also work when no dhcp servers are around. edit: To clarify a bit: The IP configuration is automatic. The problem to focus is how to tell the PC which IP in the network (or a direct connection in this vase there would only be one) belongs to the device (identity).

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• Can't access apache from outsite my local network

  - by valter

  UPDATED: Now, when I type my external ip like xxx.xxx.xxx.xxx:8079, i can access xampp defaults page. But the strange is that when someone else from outside my network, try to access it using the same ip, it doesnt work. I Think it should, because its the external ip. I'm getting crazy. I have tried for hours to access xampp defaults page from outside my local network. My ISP blocks port 80 and 8080. So I changed apache to listen to port 8079 Listen 8079 My local computer ip is 10.1.1.2 I can access the webserver, from any computer on my local network when I type http://10.1.1.2:8079 I also oppended the port 8079 on my modem, as the image shows bellow. (I think i did it right) When apache is running on my computer, if I test the port 8079 at http://canyouseeme.org/ i get the message "Success: I can see your service on xxx.xxx.xxx.xxx on port (8079) Your ISP is not blocking port 8079" If apache is not running I get "Error: I could not see your service on xxx.xxx.xxx.xxx on port (8079) Reason: Connection refused". So, it's clear that the port 8079 is oppened. But when I type xxx.xxx.xxx.xxx:8079 on google chrome for example, I get Oops! Google Chrome could not connect to xxx.xxx.xxx.xxx:8079 What can I do to solve this, to allow apache to server the pages? I don't know what else I shoud configure. Please, help me. Thanks.

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• How do I fix a permissions problem with MS Distributed File System?

  - by charlesrandall

  I have a computer that is new, Windows 7, that is supposed to have access to particular network resources on a Distributed File System. However, despite all permissions being set correctly, I have consistent trouble accessing them. For instance, I'm supposed to be able to reach \company.org\main\subdir. All the permissions have been granted, only when I try to access it by name, it tells me I don't have permission to access \main. This is where the fun starts. If I ping company.org, get the IP, replace company.org by the IP, I can then access \IP\main\subdir without any problems at all. However we have a ton of scripts and build tools that access the network resource by name. My sysadmin has found that using MS's dfsutil.exe, we can fix it temporary using this sequence of commands: C:\dfsutil.exe /pktinfo C:\dfsutil.exe /PktFlush C:\dfsutil.exe /SpcFlush C:\dfsutil.exe /PurgeMupCache C:\dfsutil.exe /pktinfo After that, everything is great... until I reboot, or until some unspecified time later where suddenly I don't have access to \main\ anymore. Hoping to find a more permanent solution than waiting for it to break and running a batch file.

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• Computers on network crashing

  - by Phil Cross

  We have recently upgraded our network to Windows 7 clients with Windows server 2008 servers. The upgrade was completed by the end of September and until now has been fine (apart from the minor bugs). Recently (within the last 2 weeks) we've notice all computers on the network (around 1000) start to slow down to the point their unusable. It starts at about 08:45 and finishes at 09:15. Because of this, we think something may be broadcasting across the network. This happens every day, between these times. I cant use my computer at all at the slowdown peak, and looking at task managers performance graphs, Physical memory is hovering around 35% and CPU usage is at 0-10% (idle) yet still crashing. I've looked on DHCPs server log and cant see anything which stands out. The only change we made prior to the slowdown was installing adobe CS6 on some computers, however the slowdown affects computers without CS6. We have 2 physical machines, each with around 5-7 virtual machines running on them with ample memory. Does anyone have any suggestions as to what we can do to narrow down whats causing the crashes? Any help, suggestions or advice would be appreciated.

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• Corrupted Laptop - Transfer Data Without My Computer (explorer.exe) Using Command Line

  - by nicorellius

  I have a laptop (Toshiba Satellite) that is pretty messed up. The person this belongs too already replaced it with a new machine. My job is to transfer all her data from this machine to disk so that I can transfer it to her. She doesn't want to lose any data (understandably so). Any operation I attempted (i.e., double clicking on any folder icon, like My Documents, My Computer, etc) resulted din a complete crash. The only good news is that I can actually start and navigate around using the command line. Also, I can access the internet. I have a network, so if I can map the drives I can get this thing figured out (hopefully). Also, I tried a USB drive but I couldn't figure out how to access it from the command line. Two questions (I need to use the command line for these): How would I go about accessing the USB drive and how can I map the shared drives on my network so that I may cd to that directory for use of the copy command?

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• Can connect to Samba server but cannot access shares?

  - by jlego

  I have setup a stand-alone box running Fedora 16 to use as a file-sharing and web development server. Needs to be able to share files with a PC running Windows 7 and a Mac running OSX Snow Leopard. I've setup Samba using the Samba configuration GUI tool. Added users to Fedora and connected them as Samba users (which are the same as the Windows and Mac usernames and passwords). The workgroup name is the same as the Windows workgroup. Authentication is set to User. I've allowed Samba and Samba client through the firewall and set the ethernet to a trusted port in the firewall. Both the Windows and Mac machines can connect to the server and view the shares, however when trying to access the shares, Windows throws error 0x80070035 " Windows cannot access \SERVERNAME\ShareName." Windows user is not prompted for a username or password when accessing the server (found under "Network Places"). This also happens when connecting with the IP rather than the server name. The Mac can also connect to the server and see the shares but when choosing a share gives the error "The original item for ShareName cannot be found." When connecting via IP, the Mac user is prompted for username and password, which when authenticated gives a list of shares, however when choosing a share to connect to, the error is displayed and the user cannot access the share. Since both machines are acting similarly when trying to access the shares, I assume it is an issue with how Samba is configured. smb.conf: [global] workgroup = workgroup server string = Server log file = /var/log/samba/log.%m max log size = 50 security = user load printers = yes cups options = raw printcap name = lpstat printing = cups [homes] comment = Home Directories browseable = no writable = yes [printers] comment = All Printers path = /var/spool/samba browseable = yes printable = yes [FileServ] comment = FileShare path = /media/FileServ read only = no browseable = yes valid users = user1, user2 [webdev] comment = Web development path = /var/www/html/webdev read only = no browseable = yes valid users = user1 How do I get samba sharing working? UPDATE: Before this box I had another box with the same version of fedora installed (16) and samba working for these same computers. I started up the old machine and copied the smb.conf file from the old machine to the new one (editing the share definitions for the new shares of course) and I still get the same errors on both client machines. The only difference in environment is the hardware and the router. On the old machine the router received a dynamic public IP and assigned dynamic private IPs to each device on the network while the new machine is connected to a router that has a static public IP (still dynamic internal IPs though.) Could either one of these be affecting Samba? UPDATE 2: As the directory I am trying to share is actually an entire internal disk, I have tried to things: 1.) changing the owner of the mounted disk from root to my user (which is the same username as on the Windows machine) 2.) made a share that only included one of the folders on the disk instead of the entire disk with my user again as the owner. Both tests failed giving me the same errors regarding the network address. UPDATE 3: Not sure exactly what I did, but now whenever I try to connect to the share on the Windows 7 client I am prompted for my username and password. When I enter the correct credentials I get an access denied message. However I did notice that under the login box "domain: WINDOWS-PC-NAME" is listed. I believe this could very well be the problem. Any suggestions? UPDATE 4: So I've completely reinstalled Fedora and Samba now. I've created a share on the first harddrive (one fedora is installed on) and I can access that fine from Windows. However when I try to share any data on the second disk, I am receiving the same error. This I believe is the problem. I think I need to change some things in fstab or fdisk or something. UPDATE 5: So in fstab I mapped the drive to automount in a folder which works correctly. I also added the samba_share_t SElinux label to the mountpoint directory which now allows me to access the shares on the Windows machine, however I cannot see any of the files in the directory on the windows machine. (They are there, I can see them in the fedora file browser locally) UPDATE 6: Figured it out. See answer below

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• OpenWorld 2012 : l'architecture multi-tenant au coeur d'Oracle 12c, une version résolument tournée vers le Cloud du célèbre SGBD

  OpenWorld 2012 : l'architecture multi-tenant au coeur d'Oracle 12c Une version résolument tournée vers le Cloud du célèbre SGBD d'entreprise Un C pour le Cloud qui sera au coeur de la prochaine version « 12c » du célèbre système de gestion de base de données d'Oracle. [IMG]http://idelways.developpez.com/news/images/cloud.jpg[/IMG] L'entreprise a annoncé une nouvelle version de son SGBD sous une approche « Multi-Tenant ». Larry Ellison a dévoilé à la conférence OpenWorld le serveur de base de données Oracle 12c, muni d'une nouvelle architecture « Multi-Tenant », basée sur le Cloud et qui sera disponible dès 2013. D'après le célèbre PDG, cette version prom...

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• WebLogic Server Weekly for March 26th, 2012: WLS 1211 Update, Java 7 Certification, Galleria, WebLogic for DBAs, REST and Enterprise Architecture, Singleton Services

  - by Steve Button

  WebLogic Server 12c Certified with Java 7 for Production Use WebLogic Server 12c (12.1.1) has been certified with JDK 7 for development usage since December and we have now completed JDK 7 certification for use with production systems. In doing so, we have updated the WebLogic Server 12c (12.1.1) distributions incorporating fixes associated with JDK 7 support as well as some bundled patches that address several issues that have been discovered since the initial release. These updated distributions are available for download from OTN and will be beneficial for all WebLogic Server 12c (12.1.1) users in general. What's New Release Notes Download Here! Updated Oracle WebLogic Server 12.1.1.0 distribution Never one to miss a trick, Markus Eisele was one of the first to notice the WebLogic Server 12c update and post a blog about it. Sources told me that as of Friday last week you have an updated version of WebLogic Server 12c on OTN. http://blog.eisele.net/2012/03/updated-oracle-weblogic-server-12110.html Using WebLogic Server 12c with Java 7 - Video To illustrate the use of Java 7 with WebLogic Server 12c, I put together a screen cam showing the creation of a domain using Java 7 and then build and deploy a simple web application that uses Java 7 syntax to show it working. Ireland OUG Presentation: WebLogic for DBAs Simon Haslam posted his slides from a presentation he gave Dublin on 21/3/12 at the OUG Ireland conference. In this presentation, he explains the core concepts and ideas behind WebLogic Server, walks through an installation and offers some tips and common gotcha's to avoid. Simon also covers some aspects of installing and use Enterprise Manager 12c. Note: I usually install the JVM and use the generic .jar installer rather than using an installer bundled with a JVM. http://www.slideshare.net/Veriton/weblogic-for-dbas-10h Slightly Retro: Jeff West on Enterprise Architecure and REST In this weeks flashback, we look at Jeff West's blog from early 2011 where he provides some thoughtful opinions on enterprise architecture and innovation, then jumps into his views on REST. After I progressed in my career and did more team-leading and architecture type roles I was ‘educated’ on what it meant to have Asynchronous and Long-Running processes as part of your Enterprise Application architecture. If I had a synchronous process then I needed a thread available to service the request and then provide the response. https://blogs.oracle.com/jeffwest/entry/weblogic_integration_wli_web_services_and_soap_and_rest_part_1 Starting Managed Servers without an Administration Server using Node Manager and WLST Blogger weblogic-tips shows how to start a managed server without going through the Administration Server, using the Node Manager and WLST. Connect WLST to a Node Manager by entering the nmConnect command. http://www.weblogic-tips.com/2012/02/18/starting-managed-servers-without-an-administration-server-using-node-manager-and-wlst/ Using WebLogic Server Singleton Services WebLogic Server has supported the notion of a Singleton Service for a number of releases, in which WebLogic Server will maintain a single instance of a configured singleton service on one managed server within a cluster. This blog demonstrates how the singleton service can be accessed and used from applications deployed on the cluster. http://buttso.blogspot.com.au/2012/03/weblogic-server-singleton-services.html

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• What should be included in risk management section of software's architecture documentation?

  - by Limbo Exile

  I am going to develop a Java application (a Spring Web application that will be used to extract data from various data sources) and I want to include risk management of the software in the architecture documentation. By risk management (I am not sure if this is the right name) I mean documenting possibilities of what can go wrong with the software and what to do in those cases. At first I tried to draft some lists, including things like database performance decrease, change of external components that the software interacts with, security breaches etc. But as I am not an experienced developer I cannot rely on those drafts, I don't think they are exhaustive. I searched web hoping to find something similar to the Joel Test or to find any other resource that will cite the most popular causes of problems that should be included and analyzed in risk management documentation, but I haven't found much. Finally, my question is: What should be included in risk management section of software's architecture documentation?

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• Can't access shared drive when connecting over VPN

  - by evolvd

  I can ping all network devices but it doesn't seem that DNS is resolving their hostnames. ipconfig/ all is showing that I am pointing to the correct dns server. I can "ping "dnsname"" and it will resolve but it wont resolve any other names. Split tunnel is set up so outside DNS is resolving fine So one issue might be DNS but I have the IP address of the server share so I figure I could just get to it that way. example: \10.0.0.1\ well I can't get to it that way either and I get "the specified network name is no longer available" I can ping it but I can't open the share. Below is the ASA config : ASA Version 8.2(1) ! hostname KG-ASA domain-name example.com names ! interface Vlan1 nameif inside security-level 100 ip address 10.0.0.253 255.255.255.0 ! interface Vlan2 nameif outside security-level 0 ip address dhcp setroute ! interface Ethernet0/0 switchport access vlan 2 ! interface Ethernet0/1 ! interface Ethernet0/2 ! interface Ethernet0/3 ! interface Ethernet0/4 ! interface Ethernet0/5 ! interface Ethernet0/6 ! interface Ethernet0/7 ! ftp mode passive clock timezone EST -5 clock summer-time EDT recurring dns domain-lookup outside dns server-group DefaultDNS name-server 10.0.0.101 domain-name blah.com access-list OUTSIDE_IN extended permit tcp any host 10.0.0.253 eq 10000 access-list OUTSIDE_IN extended permit tcp any host 10.0.0.253 eq 8333 access-list OUTSIDE_IN extended permit tcp any host 10.0.0.253 eq 902 access-list SPLIT-TUNNEL-VPN standard permit 10.0.0.0 255.0.0.0 access-list NONAT extended permit ip 10.0.0.0 255.255.255.0 10.0.1.0 255.255.255.0 pager lines 24 logging asdm informational mtu inside 1500 mtu outside 1500 ip local pool IPSECVPN-POOL 10.0.1.2-10.0.1.50 mask 255.255.255.0 icmp unreachable rate-limit 1 burst-size 1 asdm image disk0:/asdm-621.bin no asdm history enable arp timeout 14400 global (outside) 1 interface nat (inside) 0 access-list NONAT nat (inside) 1 0.0.0.0 0.0.0.0 static (inside,outside) tcp interface 10000 10.0.0.101 10000 netmask 255.255.255.255 static (inside,outside) tcp interface 8333 10.0.0.101 8333 netmask 255.255.255.255 static (inside,outside) tcp interface 902 10.0.0.101 902 netmask 255.255.255.255 timeout xlate 3:00:00 timeout conn 1:00:00 half-closed 0:10:00 udp 0:02:00 icmp 0:00:02 timeout sunrpc 0:10:00 h323 0:05:00 h225 1:00:00 mgcp 0:05:00 mgcp-pat 0:05:00 timeout sip 0:30:00 sip_media 0:02:00 sip-invite 0:03:00 sip-disconnect 0:02:00 timeout sip-provisional-media 0:02:00 uauth 0:05:00 absolute timeout tcp-proxy-reassembly 0:01:00 dynamic-access-policy-record DfltAccessPolicy aaa authentication enable console LOCAL aaa authentication http console LOCAL aaa authentication serial console LOCAL aaa authentication ssh console LOCAL aaa authentication telnet console LOCAL http server enable http 10.0.0.0 255.255.0.0 inside http 0.0.0.0 0.0.0.0 outside no snmp-server location no snmp-server contact snmp-server enable traps snmp authentication linkup linkdown coldstart crypto ipsec transform-set myset esp-aes esp-sha-hmac crypto ipsec transform-set ESP-3DES-SHA esp-3des esp-sha-hmac crypto ipsec security-association lifetime seconds 28800 crypto ipsec security-association lifetime kilobytes 4608000 crypto dynamic-map dynmap 1 set transform-set myset crypto dynamic-map dynmap 1 set reverse-route crypto map IPSEC-MAP 65535 ipsec-isakmp dynamic dynmap crypto map IPSEC-MAP interface outside crypto isakmp enable outside crypto isakmp policy 10 authentication pre-share encryption 3des hash sha group 2 lifetime 86400 crypto isakmp policy 65535 authentication pre-share encryption aes hash sha group 2 lifetime 86400 telnet 0.0.0.0 0.0.0.0 inside telnet timeout 5 ssh 0.0.0.0 0.0.0.0 inside ssh 70.60.228.0 255.255.255.0 outside ssh 74.102.150.0 255.255.254.0 outside ssh 74.122.164.0 255.255.252.0 outside ssh timeout 5 console timeout 0 dhcpd dns 10.0.0.101 dhcpd lease 7200 dhcpd domain blah.com ! dhcpd address 10.0.0.110-10.0.0.170 inside dhcpd enable inside ! threat-detection basic-threat threat-detection statistics access-list no threat-detection statistics tcp-intercept ntp server 63.111.165.21 webvpn enable outside svc image disk0:/anyconnect-win-2.4.1012-k9.pkg 1 svc enable group-policy EASYVPN internal group-policy EASYVPN attributes dns-server value 10.0.0.101 vpn-tunnel-protocol IPSec l2tp-ipsec svc webvpn split-tunnel-policy tunnelspecified split-tunnel-network-list value SPLIT-TUNNEL-VPN ! tunnel-group client type remote-access tunnel-group client general-attributes address-pool (inside) IPSECVPN-POOL address-pool IPSECVPN-POOL default-group-policy EASYVPN dhcp-server 10.0.0.253 tunnel-group client ipsec-attributes pre-shared-key * tunnel-group CLIENTVPN type ipsec-l2l tunnel-group CLIENTVPN ipsec-attributes pre-shared-key * ! class-map inspection_default match default-inspection-traffic ! ! policy-map global_policy class inspection_default inspect icmp ! service-policy global_policy global prompt hostname context I'm not sure where I should go next with troubleshooting nslookup result: Default Server: blahname.blah.lan Address: 10.0.0.101

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• Organization &amp; Architecture UNISA Studies &ndash; Chap 13

  - by MarkPearl

  Learning Outcomes Explain the advantages of using a large number of registers Discuss the way in which compilers optimize register usage Discuss the evolution of CISC machines Describe the characteristics of RISC architecture Discuss the RISC vs. CISC controversy Describe the way in which RISC and CISC design principles can be combined Instruction Execution Characteristics To understand the the line of reasoning of RISC advocates, we need a brief overview of instruction execution characteristics. These include… Operations Operands Procedure Calls These three sections can be studied in depth in the textbook at pages 503 - 505 A number of groups have come up with the conclusion that the attempt to make the instruction set architecture closer to HLLs (High Level Languages) is not the most effective design strategy. Rather HLL’s can be best supported by optimizing performance of the most time-consuming features of typical HLL programs. Generally 3 main characteristics came up to improve performance… Use a large number of registers or use a compiler to optimize register usage Careful attention needs to be paid to the design of instruction pipelines A simplified (reduced) instruction set is indicated The use of a large register optimization One of the most important design principles of RISC machines is the use of a large number of registers. The concept of register windows and the use of a large register file versus the use of cache memory are discussed. On the face of it, the use of a large set of registers should decrease the need to access memory. The design task is to organize the registers in such a fashion that this goal is realized. Read page 507 – 510 for a detailed explanation. Compiler-based register optimization   Reduced Instructions Set Architecture There are two advantages to smaller programs… Because the program takes up less memory, there is a savings in that resource (this was more compelling when memory was more expensive) Smaller programs should improve performance, and this will happen in two ways – fewer instructions means fewer instruction bytes to be fetched and in a paging environment smaller programs occupy fewer pages, reducing page faults. Certain characteristics are common to RISC processors… One instruction per cycle Register-to-register operations Simple addressing modes Simple instruction formats RISC vs. CISC After initial enthusiasm for RISC machines, there has been a growing realization that RISC designs may benefit from the inclusion of some CISC features CISC designs may benefit from the inclusion of some RISC features

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• Choices in Architecture, Design, Algorithms, Data Structures for effective RDF Reasoning and Querying in a Big Data Environment [on hold]

  - by user2891213

  As part of my academic project I would like to know what choices in Architecture, Design, Algorithms, Data Structures do we need in order to provide effective and efficient RDF Reasoning and Querying in a Big Data Environment. Basically I want to get info regarding below points: What are the Systems and Software to get appropriate Architecture? What kind of API layer(s) would we need on top of the Big Data stores, to make this possible? The Indexing structures we will need. The appropriate Algorithms, and appropriate Algorithms for Query Planning across Big Data stores. The Performance Analysis and Cost Models we will need to justify the design decisions we have made along the way. Can anyone please provide pointers.. Thanks, David

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• I can connect to Samba server but cannot access shares.

  - by jlego

  I'm having trouble getting samba sharing working to access shares. I have setup a stand-alone box running Fedora 16 to use as a file-sharing and web development server. It needs to be able to share files with a Windows 7 PC and a Mac running OSX Snow Leopard. I've setup Samba using the Samba configuration GUI tool on Fedora. Added users to Fedora and connected them as Samba users (which are the same as the Windows and Mac usernames and passwords). The workgroup name is the same as the Windows workgroup. Authentication is set to User. I've allowed Samba and Samba client through the firewall and set the ethernet to a trusted port in the firewall. Both the Windows and Mac machines can connect to the server and view the shares, however when trying to access the shares, Windows throws error: 0x80070035 " Windows cannot access \\SERVERNAME\ShareName." Windows user is not prompted for a username or password when accessing the server (found under "Network Places"). This also happens when connecting with the IP rather than the server name. The Mac can also connect to the server and see the shares but when choosing a share gives the error: The original item for ShareName cannot be found. When connecting via IP, the Mac user is prompted for username and password, which when authenticated gives a list of shares, however when choosing a share to connect to, the error is displayed and the user cannot access the share. Since both machines are acting similarly when trying to access the shares, I assume it is an issue with how Samba is configured. smb.conf: [global] workgroup = workgroup server string = Server log file = /var/log/samba/log.%m max log size = 50 security = user load printers = yes cups options = raw printcap name = lpstat printing = cups [homes] comment = Home Directories browseable = no writable = yes [printers] comment = All Printers path = /var/spool/samba browseable = yes printable = yes [FileServ] comment = FileShare path = /media/FileServ read only = no browseable = yes valid users = user1, user2 [webdev] comment = Web development path = /var/www/html/webdev read only = no browseable = yes valid users = user1 How do I get samba sharing working? UPDATE: I Figured it out, it was because I was sharing a second hard drive. See checked answer below. Speculation 1: Before this box I had another box with the same version of fedora installed (16) and samba working for these same computers. I started up the old machine and copied the smb.conf file from the old machine to the new one (editing the share definitions for the new shares of course) and I still get the same errors on both client machines. The only difference in environment is the hardware and the router. On the old machine the router received a dynamic public IP and assigned dynamic private IPs to each device on the network while the new machine is connected to a router that has a static public IP (still dynamic internal IPs though.) Could either one of these be affecting Samba? Speculation 2: As the directory I am trying to share is actually an entire internal disk, I have tried these things: 1.) changing the owner of the mounted disk from root to my user (which is the same username as on the Windows machine) 2.) made a share that only included one of the folders on the disk instead of the entire disk with my user again as the owner. Both tests failed giving me the same errors regarding the network address. Speculation 3: Whenever I try to connect to the share on the Windows 7 client I am prompted for my username and password. When I enter the correct credentials I get an access denied message. However I did notice that under the login box "domain: WINDOWS-PC-NAME" is listed. I believe this could very well be the problem. Speculation 4: So I've completely reinstalled Fedora and Samba now. I've created a share on the first harddrive (one fedora is installed on) and I can access that fine from Windows. However when I try to share any data on the second disk, I am receiving the same error. This I believe is the problem. I think I need to change some things in fstab or fdisk or something. Speculation 5: So in fstab I mapped the drive to automount in a folder which works correctly. I also added the samba_share_t SElinux label to the mountpoint directory which now allows me to access the shares on the Windows machine, however I cannot see any of the files in the directory on the windows machine. (They are there, I can see them in the fedora file browser locally)

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• Postfix/SMTPD Relay Access Denied when sending outside the network

  - by David

  I asked a very similar question some 4 or 5 months ago, but haven't tracked down a suitable answer. I decided to post a new question so that I can ... a) Post updated info b) post my most current postconf -n output When a user sends mail from inside the network (via webmail) to email addresses both inside and outside the network, the email is delivered. When a user with an email account on the system sends mail from outside the network, using the server as the relay, to addresses inside the network, the email is delivered. But [sometimes] when a user connects via SMTPD to send email to an external address, a Relay Access Denied error is returned: Feb 25 19:33:49 myers postfix/smtpd[8044]: NOQUEUE: reject: RCPT from host-68-169-158-182.WISOLT2.epbfi.com[68.169.158.182]: 554 5.7.1 <host-68-169-158-182.WISOLT2.epbfi.com[68.169.158.182]>: Client host rejected: Access denied; from=<[email protected]> to=<[email protected]> proto=ESMTP helo=<my-computer-name> Feb 25 19:33:52 myers postfix/smtpd[8044]: disconnect from host-68-169-158-182.WISOLT2.epbfi.com[68.169.158.182] Sending this through Microsoft Outlook 2003 generates the above log. However, sending through my iPhone, with the exact same settings, goes through fine: Feb 25 19:37:18 myers postfix/qmgr[3619]: A2D861302C9: from=<[email protected]>, size=1382, nrcpt=1 (queue active) Feb 25 19:37:18 myers amavis[2799]: (02799-09) FWD via SMTP: <[email protected]> -> <[email protected]>,BODY=7BIT 250 2.0.0 Ok, id=02799-09, from MTA([127.0.0.1]:10025): 250 2.0.0 Ok: queued as A2D861302C9 Feb 25 19:37:18 myers amavis[2799]: (02799-09) Passed CLEAN, [68.169.158.182] [68.169.158.182] <[email protected]> -> <[email protected]>, Message-ID: <[email protected]>, mail_id: yMLvzVQJloFV, Hits: -9.607, size: 897, queued_as: A2D861302C9, 6283 ms Feb 25 19:37:18 myers postfix/lmtp[8752]: 2ED3A1302C8: to=<[email protected]>, relay=127.0.0.1[127.0.0.1]:10024, delay=6.6, delays=0.25/0.01/0.19/6.1, dsn=2.0.0, status=sent (250 2.0.0 Ok, id=02799-09, from MTA([127.0.0.1]:10025): 250 2.0.0 Ok: queued as A2D861302C9) Feb 25 19:37:18 myers postfix/qmgr[3619]: 2ED3A1302C8: removed Outgoing Settings on Outlook 2003 match the settings on my iPhone: SMTP server: mail.my-domain.com Username: My full email address Uses SSL Server Port 587 Now, here's postconf -n. I realize the "My Networks" Parameter is a bit nasty. I have these IP addresses in here for just this reason, as others have been complaining of this problem too: alias_database = hash:/etc/postfix/aliases alias_maps = $alias_database append_dot_mydomain = no biff = no broken_sasl_auth_clients = yes command_directory = /usr/sbin config_directory = /etc/postfix content_filter = amavisfeed:[127.0.0.1]:10024 daemon_directory = /usr/libexec/postfix debug_peer_level = 2 disable_vrfy_command = yes html_directory = no inet_interfaces = all mail_owner = postfix mail_spool_directory = /var/spool/mail mailbox_size_limit = 0 mailq_path = /usr/bin/mailq manpage_directory = /usr/share/man message_size_limit = 20480000 mydestination = $myhostname, localhost, localhost.$mydomain mydomain = my-domain.com myhostname = myers.my-domain.com mynetworks = 127.0.0.0/8, 74.125.113.27, 74.125.82.49, 74.125.79.27, 209.85.161.0/24, 209.85.214.0/24, 209.85.216.0/24, 209.85.212.0/24, 209.85.160.0/24 myorigin = $myhostname newaliases_path = /usr/bin/newaliases queue_directory = /var/spool/postfix readme_directory = /usr/share/doc/postfix-2.3.3/README_FILES receive_override_options = no_address_mappings recipient_delimiter = + relay_domains = $mydestination sample_directory = /usr/share/doc/postfix-2.3.3/samples sendmail_path = /usr/sbin/sendmail setgid_group = postdrop smtp_bind_address = my-primary-server's IP address smtpd_banner = mail.my-domain.com smtpd_helo_required = yes smtpd_sasl_auth_enable = yes smtpd_sasl_path = private/auth smtpd_sasl_type = dovecot smtpd_tls_auth_only = yes smtpd_tls_cert_file = /etc/ssl/mailserver/postfix.pem smtpd_tls_key_file = /etc/ssl/mailserver/private/postfix.pem smtpd_tls_loglevel = 3 smtpd_tls_received_header = no smtpd_tls_session_cache_timeout = 3600s smtpd_use_tls = yes tls_random_source = dev:/dev/urandom unknown_local_recipient_reject_code = 554 virtual_alias_maps = mysql:/etc/postfix/mysql-virtual-alias-maps.cf,mysql:/etc/postfix/mysql-email2email.cf virtual_gid_maps = static:5000 virtual_mailbox_base = /var/vmail virtual_mailbox_domains = mysql:/etc/postfix/mysql-virtual-mailbox-domains.cf virtual_mailbox_maps = mysql:/etc/postfix/mysql-virtual-mailbox-maps.cf virtual_minimum_uid = 5000 virtual_transport = dovecot virtual_uid_maps = static:5000 If anyone has any ideas and can help me finally solve this issue once and for all, I'd be eternally grateful.

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• Tunnel is up but cannot ping directly connected network

  - by drmanalo

  We configured a site-to-site VPN and here is the topology. I control the network on the left but not the one on the right. All devices in our network has public IPs. Server---ASA5505---Cisco887======Internet=====ASA5510---devices I can see the tunnel is up and can do extended ping using a loopback interface. From the 10.175 and 10.165 networks, they can also ping my loopback address. I can also dial in using a Cisco VPN client, and can connect to the devices on the right. #show crypto session Crypto session current status Interface: Vlan3 Profile: xxx-profile Session status: UP-ACTIVE Peer: 213.121.x.x port 500 IKEv1 SA: local 77.245.x.x/500 remote 213.121.x.x/500 Active IPSEC FLOW: permit ip 10.0.20.0/255.255.255.240 10.175.0.0/255.255.128.0 Active SAs: 0, origin: crypto map IPSEC FLOW: permit ip 10.0.20.0/255.255.255.240 10.165.0.0/255.255.192.0 Active SAs: 2, origin: crypto map #ping 10.165.29.39 source loopback 2 Type escape sequence to abort. Sending 5, 100-byte ICMP Echos to 10.165.29.39, timeout is 2 seconds: Packet sent with a source address of 10.0.20.1 !!!!! Success rate is 100 percent (5/5), round-trip min/avg/max = 16/17/20 ms My problem is the devices on the right cannot reach my server. They could only ping the loopback address and nothing else. I'm pasting some diagnostics related to routing thinking perhaps routing is my issue. I can paste all the running-config on my side of network if needed. #show ip int brief Interface IP-Address OK? Method Status Protocol ATM0 unassigned YES NVRAM administratively down down Ethernet0 unassigned YES NVRAM administratively down down FastEthernet0 unassigned YES unset up up connected to ASA FastEthernet1 unassigned YES unset administratively down down FastEthernet2 unassigned YES unset administratively down down FastEthernet3 unassigned YES unset up up Loopback1 10.0.20.65 YES NVRAM up up Loopback2 10.0.20.1 YES NVRAM up up Virtual-Template1 77.245.x.x YES unset up down Virtual-Template2 77.245.x.x YES unset up down Vlan1 unassigned YES unset down down Vlan3 77.245.x.x YES NVRAM up up connected to the Internet #show run | section ip route ip route 0.0.0.0 0.0.0.0 77.245.x.x ip route 213.121.240.36 255.255.255.255 Vlan3 #show access-list Extended IP access list 102 10 permit ip 10.0.20.0 0.0.0.15 10.175.0.0 0.0.127.255 (3332 matches) 20 permit ip 10.0.20.0 0.0.0.15 10.165.0.0 0.0.63.255 (3498 matches) #show vlan-switch VLAN Name Status Ports ---- -------------------------------- --------- ------------------------------- 1 default active 3 VLAN0003 active Fa0, Fa1, Fa2, Fa3 1002 fddi-default act/unsup 1003 token-ring-default act/unsup 1004 fddinet-default act/unsup 1005 trnet-default act/unsup #show ip route Codes: L - local, C - connected, S - static, R - RIP, M - mobile, B - BGP D - EIGRP, EX - EIGRP external, O - OSPF, IA - OSPF inter area N1 - OSPF NSSA external type 1, N2 - OSPF NSSA external type 2 E1 - OSPF external type 1, E2 - OSPF external type 2 i - IS-IS, su - IS-IS summary, L1 - IS-IS level-1, L2 - IS-IS level-2 ia - IS-IS inter area, * - candidate default, U - per-user static route o - ODR, P - periodic downloaded static route, H - NHRP, l - LISP + - replicated route, % - next hop override Gateway of last resort is 77.245.x.x to network 0.0.0.0 S* 0.0.0.0/0 [1/0] via 77.245.x.x 10.0.0.0/8 is variably subnetted, 5 subnets, 3 masks C 10.0.20.0/28 is directly connected, Loopback2 L 10.0.20.1/32 is directly connected, Loopback2 C 10.0.20.64/28 is directly connected, Loopback1 L 10.0.20.65/32 is directly connected, Loopback1 S 10.165.0.0/18 [1/0] via 213.121.x.x 77.0.0.0/8 is variably subnetted, 3 subnets, 3 masks S 77.0.0.0/8 [1/0] via 77.245.x.x C 77.245.x.x/29 is directly connected, Vlan3 L 77.245.x.x/32 is directly connected, Vlan3 213.121.x.0/32 is subnetted, 1 subnets S 213.121.x.x is directly connected, Vlan3 I read some of the posts here which lead to NATing issue but I'not sure of my next step. Should I translate my public address to private and route it to the loopback address? (only guessing) CISCO VPN site to site Site-to-Site VPN between two ASA 5505s only working in one direction Hope someone could help. Thanks in advance!

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• Can't get network bridging to work

  - by Antonis Christofides

  I'm trying to make network bridging to work on a Debian squeeze (I'm experimenting in order to make a QEMU/KVM virtual machine that will be visible to the outside network as if it were a distinct machine). The problem is that when I type brctl addif br0 eth0 then I lose connectivity to the network until I type brctl delif br0 eth0. More specifically, here's how my machine looks like before I do anything (essentially eth0 is listening on 147.102.160.153): root@laura:/home/anthony# ip addr show 1: lo: <LOOPBACK,UP,LOWER_UP> mtu 16436 qdisc noqueue state UNKNOWN link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00 inet 127.0.0.1/8 scope host lo inet6 ::1/128 scope host valid_lft forever preferred_lft forever 2: eth0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast state UP qlen 1000 link/ether 8c:73:6e:db:1c:1b brd ff:ff:ff:ff:ff:ff inet 147.102.160.153/24 brd 147.102.160.255 scope global eth0 inet6 2001:648:2000:a0:8e73:6eff:fedb:1c1b/64 scope global dynamic valid_lft 2591848sec preferred_lft 604648sec inet6 fe80::8e73:6eff:fedb:1c1b/64 scope link valid_lft forever preferred_lft forever 3: wlan0: <BROADCAST,MULTICAST> mtu 1500 qdisc mq state DOWN qlen 1000 link/ether 4c:ed:de:8e:44:d7 brd ff:ff:ff:ff:ff:ff 4: vboxnet0: <BROADCAST,MULTICAST> mtu 1500 qdisc noop state DOWN qlen 1000 link/ether 0a:00:27:00:00:00 brd ff:ff:ff:ff:ff:ff 5: pan0: <BROADCAST,MULTICAST> mtu 1500 qdisc noop state DOWN link/ether ee:7c:88:59:d0:e8 brd ff:ff:ff:ff:ff:ff Now let me add the bridge: root@laura:/home/anthony# brctl addbr br0 root@laura:/home/anthony# ip tuntap add dev tap0 mode tap root@laura:/home/anthony# ip link set tap0 up root@laura:/home/anthony# brctl addif br0 tap0 Until here everything continues to work normally. Finally, I try to add eth0 to the bridge: root@laura:/home/anthony# brctl addif br0 eth0 At this point, I no longer have a network connection. If I try to ping something, it tells "Destination Host Unreachable". The output of ip addr show seems normal: root@laura:/home/anthony# ip addr show 1: lo: <LOOPBACK,UP,LOWER_UP> mtu 16436 qdisc noqueue state UNKNOWN link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00 inet 127.0.0.1/8 scope host lo inet6 ::1/128 scope host valid_lft forever preferred_lft forever 2: eth0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast state UP qlen 1000 link/ether 8c:73:6e:db:1c:1b brd ff:ff:ff:ff:ff:ff inet 147.102.160.153/24 brd 147.102.160.255 scope global eth0 inet6 2001:648:2000:a0:8e73:6eff:fedb:1c1b/64 scope global dynamic valid_lft 2591908sec preferred_lft 604708sec inet6 fe80::8e73:6eff:fedb:1c1b/64 scope link valid_lft forever preferred_lft forever [snip wlan0, vboxnet0 and pan0, which are down and irrelevant] 8: br0: <BROADCAST,MULTICAST> mtu 1500 qdisc noop state DOWN link/ether 16:30:f2:67:ab:75 brd ff:ff:ff:ff:ff:ff 9: tap0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast state UNKNOWN qlen 500 link/ether 16:30:f2:67:ab:75 brd ff:ff:ff:ff:ff:ff inet6 fe80::1430:f2ff:fe67:ab75/64 scope link valid_lft forever preferred_lft forever Also: root@laura:/home/anthony# route -n Kernel IP routing table Destination Gateway Genmask Flags Metric Ref Use Iface 147.102.160.0 0.0.0.0 255.255.255.0 U 1 0 0 eth0 169.254.0.0 0.0.0.0 255.255.0.0 U 1000 0 0 eth0 0.0.0.0 147.102.160.200 0.0.0.0 UG 0 0 0 eth0 I can't understand what I'm doing wrong. I want the machine to continue to listen on 147.102.160.153 on eth0, and in addition to that I want to have a tap0 interface, bridged to eth0, that will be available to the guest machine so that the latter listens on another ip address (say 147.102.160.205). (If there's another way to achieve what I want, I'm also interested.)

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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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• Patterns for non-layered applications

  - by Paul Stovell

  In Patterns of Enterprise Application Architecture, Martin Fowler writes: This book is thus about how you decompose an enterprise application into layers and how those layers work together. Most nontrivial enterprise applications use a layered architecture of some form, but in some situations other approaches, such as pipes and filters, are valuable. I don't go into those situations, focussing instead on the context of a layered architecture because it's the most widely useful. What patterns exist for building non-layered applications/parts of an application? Take a statistical modelling engine for a financial institution. There might be a layer for data access, but I expect that most of the code would be in a single layer. Would you still expect to see Gang of Four patterns in such a layer? How about a domain model? Would you use OO at all, or would it be purely functional? The quote mentions pipes and filters as alternate models to layers. I can easily imagine a such an engine using pipes as a way to break down the data processing. What other patterns exist? Are there common patterns for areas like task scheduling, results aggregation, or work distribution? What are some alternatives to MapReduce?

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• How to understand other people's CSS architectures?

  - by John

  I am reasonably good with CSS. However, when working with someone else's CSS, it's difficult for me to see the "bigger picture" in their architecture (but i have no problem when working with a CSS sheet I wrote myself). For example, I have no problems using Firebug to isolate and fix cross browser compatibility issues, or fixing a floating issue, or changing the height on a particular element. But if I'm asked to do something drastic such as, "I want the right sidebars of pages A, B, C and D to have a red border. I want the right side bars of pages E, F and G to have a blue border if and only if the user mouses over", then it takes me time a long time to map out all the CSS inheritance rules to see the "bigger picture". For some reason, I don't encounter the same difficulty with backend code. After a quick debriefing of how a feature works, and a quick inspection of the controller and model code, I will feel comfortable with the architecture. I will think, "it's reasonable to assume that there will be an Employee class that inherits from the Person Class that's used by a Department controller". If I discover inconvenient details that aren't consistent with overall architectural style, I am confident that I can hammer things back in place. With someone else's CSS work, it's much harder for me to see the "relationships" between different classes, and when and how the classes are used. When there are many inheritance rules, I feel overwhelmed. I'm having trouble articulating my question and issues... All I want to know is, why is it so much harder for me to see the bigger picture in someone else's CSS architecture than compared to someone else's business logic layer? **Does it have any thing to do with CSS being a relatively new technology, and there aren't many popular design patterns?

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• Block diagram containing computer buses,motherboard..

  - by learnerforever

  Hi all, I am trying to understand computer architecture. In particular: - Physical view i.e. what all is packed inside the motherboard and what all outside - Conceptual view. how processor,memory,peripherals are connected. I am getting confused among various buses like local bus,PCI bus, SCSI bus,ISA bus,USB bus. I am looking for block diagrams. How is the USB port connected to processor ultimately? through PCI bus etc? Why do we have so many buses? What was it like before SCSI/IDE came? Does the diagram at : http://www.vaughns-1-pagers.com/computer/pc-block-diagram.htm look correct? It shows no connection between PCI bus and SCSI bus. Is that correct? I would greatly appreciate any other link especially of block diagrams/anatomy and not just textual writeup. Thanks,

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