Technology And Computer|

Article by Moshiachy Thisyday

To earn your CCNA or CCNP certification, you’ve got to understand the basics of trunking. This is not just a CCNA topic – it’s essential to have a complicated understanding of trunking and etherchannels to move the BCMSN exam and earn your CCNP as well. Before we deal with those superior topics, though, it’s worthwhile to master the basics!

A trunk allows inter-VLAN visitors to move between immediately connected switches. By default, a trunk port is a member of all VLANs, so visitors for any and all VLANs can travel throughout this trunk. That includes broadcast site visitors!

The default mode of a swap port does differ between fashions, so always check your documentation. On Cisco 2950 switches, every single port is in dynamic fascinating mode by default, that means that every port is actively attempting to trunk. On these switches, the only motion wanted from us is to physically join them with a crossover cable. In just a few seconds, the port light turns inexperienced and the trunk is up and running. The command show interface trunk will confirm trunking.

How does the receiving change know what VLAN the body belongs to? The frames are tagged by the transmitting change with a VLAN ID, reflecting the number of the VLAN whose member ports should receive this frame. When the body arrives at the remote change, that change will look at this ID and then ahead the frame appropriately.

There are main trunking protocols it’s essential to understand and evaluate successfully, these being ISL and IEEE 802.1Q. Let’s check out the main points of ISL first.

ISL is a Cisco-proprietary trunking protocol, making it unsuitable for a multivendor environment. That’s one disadvantage, but there are others. ISL will place both a header and trailer onto the body, encapsulating it. This increases the overhead on the trunk line.

You know that the default VLAN is also referred to as the “native VLAN”, and another disadvantage to ISL is that ISL does not use the concept of the native VLAN. Which means that every single body transmitted across the trunk will likely be encapsulated.

The 26-byte header that’s added to the frame by ISL accommodates the VLAN ID; the 4-byte trailer comprises a Cyclical Redundancy Test (CRC) value. The CRC is a frame validity scheme that checks the frame’s integrity.

In flip, this encapsulation leads to one other potential issue. ISL encapsulation adds 30 bytes complete to the dimensions of the frame, potentially making them too massive for the switch to handle. (The maximum size for an Ethernet frame is 1518 bytes.)

IEEE 802.1q differs considerably from ISL. In distinction to ISL, dot1q doesn’t encapsulate frames. A four-byte header is added to the body, resulting in much less overhead than ISL. If the body is destined for hosts residing in the native VLAN, that header is not added. Because the header is barely four bytes in dimension, and is not even placed on each frame, using dot1q lessens the possibility of outsized frames. When the remote port receives an untagged body, the swap knows that these untagged frames are destined for the native VLAN.

Knowing the main points is the distinction between passing and failing your CCNA and CCNP exams. Maintain learning, get some fingers-on practice, and you’re in your approach to Cisco certification success!

BGP is without doubt one of the most complicated matters you’ll examine when pursuing your CCNP, if not essentially the most complex. I do know from personal expertise that when I was incomes my CCNP, BGP is the topic that gave me the most trouble at first. One thing I preserve reminding today’s CCNP candidates about, though, is that no Cisco technology is unimaginable to grasp for those who just break it down and understand the fundamentals before you start making an attempt to know the more advanced configurations.

BGP attributes are one such topic. You have bought well-identified necessary, well-known discretionary, transitive, and non-transitive. Then you definately’ve bought each particular person BGP attribute to recollect, and the order wherein BGP considers attributes, and what attributes even are… and a lot more! As with every other Cisco matter, we have to stroll before we can run. Let’s check out what attributes are and what they do in BGP.

BGP attributes are much like what metrics are to OSPF, RIP, IGRP, and EIGRP. You won’t see them listed in a routing table, but attributes are what BGP considers when selecting the perfect path to a destination when multiple legitimate (loop-free) paths exist.

When BGP has to decide between such paths, there’s an order by which BGP considers the trail attributes. For success on the CCNP exams, you’ll want to know this order. BGP looks at path attributes on this order:

Highest weight (Cisco-proprietary BGP worth)

Highest local preference (LOCAL_PREF)

Favor locally originated route.

Shortest AS_PATH is preferred.

Choose route with lowest origin code. Inner paths are most popular over exterior paths, and external paths are preferred over paths with an origin of “incomplete”.Lowest multi-exit discriminator (MED)

Exterior BGP routes most popular over Inside BGP routes.

If no external route, choose path with lowest IGP value to the following-hop router for iBGP.

Choose most recent route.

Select lowest BGP RID (Router ID).

If you do not know what these values are, or how they’re configured, do not panic! The subsequent several parts of this BGP tutorial will explain it all. So spend some time studying this order, and partly II of this free BGP tutorial, we’ll look at every of these values in detail. Preserve studying

The LINUX operating system is very much similar to UNIX and has derived many basic design principles from it. Day by day, LINUX OS has improved upon its previous versions and indeed has incorporated a number of distinguishable features over other operating systems. In LINUX, disk drives are mounted through file system volume label and not the device path. This is a newer concept applied in LINIX in order to avoid the ambiguity in distinguishing after a disk has been removed and some other have been inserted with the same device path. However, if there is corruption to the volume label, the situation becomes more complex, keeping the data from the drive completely inaccessible and a LINUX data recovery utility is a must to recover the inaccessible data.

To be a bit more elaborative, suppose, your system disk is at /dev/sda2. The system may have mapped another disk as /dev/sda2 and hence, your fstab, where all entries of the mounted disks are there, will be messed up making your system start improperly. At times, such issues can cause huge loss of data.

These kinds of situation may fire the command fsck automatically to check the LINUX volumes each time the system boots-up. As fsck, checks for file system errors and tries to repair the same, it may take a significant amount of time. Any power surge or system crash during the process may cause serious system instability and data loss. This is an added problem that may further flash a warning message and further increase the chances that your LINUX volumes become inaccessible. The message may read as below:

“Warning: invalid flag 0×0000 of partition table 4 will be corrected by w(rite)”

The warning message tells that the disk label has been corrupted and that is why the data in the drive is inaccessible. If running Disk Utility or fsck command fails, you have to restore the data from the backup. However, if backup of your data is not available, run a reliable Linux disk recovery software to recover the data.

LINUX data recovery software are designed with powerful scanning algorithms that can recover any deleted, formatted or inaccessible data with ease irrespective of the data loss situation.

Among many names, Stellar Phoenix Linux Data Recovery is tried and appreciated by many users. The application can successfully recover your lost, formatted or inaccessible data from FAT32,FAT16,FAT12,Ext3,Ext4,Ext2 file system based LINUX volumes.

Kuldeep a techno geek is a technical writer doing research on different file system in linux like Ext2, Ext3. And Ext4. He is also interested in linux data recovery, And Ext3 recovery. He is currently working with http://www.data-recovery-linux.com/

In Linux computers, dd (data definition) command-line utility offers several advantages such as converting raw data or low-level copying of data from hard drive to any other storage media. The command is used to copy the file system and is capable of copying specified number of data blocks or bytes. Furthermore, this tool allows you to copy data blocks rearwards, so that in case of any problem in block at some point, data that is stored after and before string would be copied. But incorrect use of parameters in this command may lead to serious data loss situations and need Linux Data Recovery to be sorted out.

This is a useful command-line tool in Linux that helps you to carry out quick and easy recovery in case of any damage to your system and data loss. This command enables you to create image of even entire Linux volume and restore it in case of any damage. On new hard drive, target partition is created having same size and structure as of the failed one. Then this utility is used for copying data from source drive.

Although, the process of this command it quite safe and easy, but a minor mistake during operation might cause disastrous situations. Performing low-level operations on hard drive, if the ‘of’ and ‘if’ parameters are get reversed accidentally. This behavior of Linux operating system renders all of your valuable data inaccessible and cause data loss. At this point, you need to perform Linux Recovery by resolving it to access your valuable data.

You much also consider the block size that has to be copied. The cont=noerror, synchronization option that is used to copy data and files, ignores remainder of block and then replaces it with zero bytes. Thus if block size is large, complete Data Recovery Linux could not be guaranteed.

In such situations, you need to methodically scan the entire hard drive using powerful and advanced scanning algorithms. This is best possible using efficient and highly automated third-party Linux Data Recovery software.

The applications come equipped with simple and self-descriptive user interface and thus let you carry out recovery on your own, without demanding sound and prior technical skills. They are built-with read-only and non-destructive conduct and thus do not alter original data on the drive.

Stellar Phoenix Linux Data Recovery is the most effective solution for all your data loss problems. The tool recovers data from all Ext4, Ext3, Ext2, FAT12, FAT16 and FAT32 hard drive volumes. It works well with all major distributions of Linux operating systems including Fedora, Red Hat, Debian, SUSE and Ubuntu.

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Data loss is a horrible reality and it may occur to any system, nevertheless of the hardware and system configuration. You can prevent such situations by creating a reliable and complete backup of your storage media. In Linux operating system, you can use mondoarchive command for this purpose. If you have a complete backup of your data, you can prevent need of Linux Data Recovery in case of any mishap.

The mondoarchive command backups a subset of all your files, whole file system, or even the images of non-Linux file systems to tape, ISO images, CDs, or an NFS (Network File System) mount. In case of critical data loss situations, you would be able to easily restore all your data and information, taking your system from mere metal state to its original state if required.

This command-line utility provides following two parameters for different operations-

-O: With this parameter mondoarchive backs up entire file system to the CD, ISO image, tape or to NFS volume. A special boot CD or the boot floppies would be created to enable you to restore data from the bare metal if required.
-V: With this parameter mondoarchive command verifies backup against the live Linux file system. The option might be used in the combination with -O parameter for verifying the backup after its creation, or independently to check how much the live Linux file system has modified since backup was created.

You can call the mondoarchive command without flags for making this auto-detect as many configuration settings as possible, ask you for the rest and then create backup and verify the operating system or the subset thereof.
In order to restore data from backup, you can either run the mondorestore from command line or boot your system from emergency floppies/CD generated while backing up the data. The latter would prove helpful if gremlin wipes the drive.

In case if the backup gets damage or the backup media fails, you can not restore data from backup and need to opt for Data Recovery Linux. The Linux Recovery in such situations is possible through third-party applications.
The tools are known as Linux Data Recovery software. They use high-end scanning techniques to methodically scan the entire hard drive and retrieve all of the lost data. With rich graphical user interface and read-only conduct, the utilities are easy and safe to use.

Stellar Phoenix Linux Data Recovery is the most effective and advanced application for absolute recovery of all your lost data. It recovers data from Ext4, Ext3, Ext2, FAT32, FAT16, and FAT12 file system volumes. The software works well with all major distributions of Linux operating system including Fedora, Ubuntu, SUSE, Red Hat, and Debian.

In Linux operating system, you should arrange to mount root file system as read-only to start with at boot time. If required then remount the file system in read/write mode. Most of the Linux distributions follow this process. If your operating system does not do this, you must read the documentation and then find out how to set your file system to follow this process.

You are required to specify -n option to mount the file system so that it does not try to update the /etc/mtab directory, otherwise the file system will fail and you will not be able to access data from it. It might cause data loss in some situations and require Linux Data Recovery to be sorted out. When a file system failure occurs on Linux file system, you generally encounters following error messages, which may stop the functionality of your system:

“EXT2-fs warning: maximal count reached.” This error message is caused by Linux operating system kernel when it mounts the file system, which is marked as clean but the number of mounts since check has reached predefined value. It might sometimes cause file system corruption and put you in need of Data Recovery Linux. The possible solution to resolve this problem is to install latest version of ext2fs utilities. You can check maximum number of counts by using tune2fs utility. “Cannot read table of mounted file systems.” You encounter this problem when the file system data structures like /etc/mtab or /etc/fstab gets damaged. If you’ve a new version of mount, then you should empty or delete the /etc/mtab file during boot. When these data structures get damaged, file system corruption occurs and you come across significant data loss circumstances.

In order to sort out the file system corruption problem, you are required to format the hard drive and reinstall operating system. This process will replace your damaged file system with new one and make your system working. But this process has a downside that it removes all of the data from hard drive and cause complete data loss that requires Data Recovery Linux for retrieving data. Recovery is possible through third-party applications, known as Linux Recovery software. The tools thoroughly scan the affected hard drive retrieve all of the lost data from it. They are completely safe and easy to use.

Stellar Phoenix Linux Data Recovery is the best ever made and the most advanced application that handles all types of data loss situations. It is compatible with most major distributions of Linux including Debian, RedHat, SUSE and Fedora. The software supports recovery from Ext4, Ext3, Ext2 and ReiserFS file system volumes.

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In Linux operating system, GPT (GParted) is a useful tool that facilitates you to create, resize, move, delete, copy and check the hard drive partitions/volumes. It also copy file system on newly created partitions. It is helpful to create space to install new operating system, copying data stored on hard drive, mirroring one volume with another and recognizing disk usage. In some cases, using this tool may become problematic. It might damaged Linux superblock and lead to critical situations of system inaccessibility and possibly data loss. At this point, you are required to opt for Linux Data Recovery to get your precious and business-critical data back.

Sometimes, when the disk resizing, copying or any other GParted process is running, few read/write errors might terminate the phenomenon. Subsequent to this serious incident, your hard drive volumes could not mount and you come across a number of error message. In such circumstances, when you run the fsck utility after rebooting the system to check integrity and consistency of file system and hard drive, conditions could remain same. Situation becomes critical on every attempt to fix this issue. Linux operating system superblock may get damaged and give you that indication through following error message:

“superblock corrupted, run with -b 32768”

Superblock is a metadata structure of Linux operating system that keeps record of all file system characteristics such as size, block size, empty and filled blocks, respective counts, location and size of Inode tables, size of block groups, disk block map and the disk usage information. When it gets damaged, you can not access data from your hard drive and Data Recovery Linux is required.

Linux file system keeps redundant copies of the superblock. You can correct the problem by using any of them. You can search and use an alternative superblock with the help of ‘mkfs -n’ command.

If the above method can not help you to sort out the issue, Linux Recovery is the way to go for successful retrieval of your valuable data. Recovery is potential through advanced third-party applications, known as Linux Recovery Software.

The tools powerful and efficient scanning mechanisms to methodically scan whole hard drive and extract all of the lost, missing or inaccessible data from it. With read-only conduct and rich graphical user interface, the software are pretty safe and easy to use.

Stellar Phoenix Linux Data Recovery is an advanced and robust application for assured recovery in all data loss situations. The software recovers data from Ext4, Ext3, Ext2, FAT32, FAT16 and FAT12 file system partitions. It works well with most major distributions of Linux including Debian, SUSE, Red Hat, Fedora and Mandriva.

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All the data files that are accessible in Linux based computers are placed in a big tree, called root directory and denoted as ‘/’, in an organized form. These data files might be spread out over various devices. The mount command in Linux operating system allows you to attach a file system on a data storage media to the root directory. However, if the file system is faulty and you run fsck utility to fix the problem after mounting the disk using this command, severe file system corruption occurs. It causes critical data loss situations and calls for Linux data recovery.

The mount command tells the Linux kernel to attach the file system found on your hard drive volume in the /dir directory. The previous owner, mode, and contents of the directory become invisible after mounting, and as long as the file system stays mounted, the /dir pathname refers to the root of file system on Linux hard drive volume.

The following three types of invocations of mount command don’t actually mount the volume:

·     mount -h- It prints the help message on screen.

·     mount -V- This invocation prints the version string.

·     Mount [-l] [-t type]- The option lists all the mounted file systems that are of type “type” on your Linux hard drive. The -l option adds labels (like ext2, ext3) in the listing.

In current versions of Linux operating system, it is possible to mark the mount and submounts as private, shared, unbindable, or slave. The shared mount gives you an option to create mirrors of the mount.

Mount is an essential process for accessing data from any Linux hard drive volume. If the drive is not mountable, it cannot be accessed. Sometimes, when you try to mount a Linux volume, you come across the following error message that puts you in need of data recovery Linux:

“Wrong fs type, bad option, bad superblock on /dev/hda8, missing codepage or helper program, or other error. In some cases useful info is found in syslog – try dmesg | tail or so”

This problem is caused by dirty or corrupt file system. In such cases, you need to use Linux recovery software to get your mission-critical data back. The Linux data recovery applications enable you to thoroughly scan the affected Linux hard drive using advanced scanning algorithms.

Stellar Phoenix Linux Data Recovery is the best solution to ensure absolute recovery in all Linux data loss situations. The software recovers lost Linux data from Ext4, Ext3, Ext2, FAT32, FAT16, and FAT12 file system volumes. It works well with all major distributions of Linux operating system, including SUSE, Mandriva, Red Hat, Debian, and Ubuntu.