Diagnostics View

In this view IntraVUE™ allows you to see CRChe cyclic redundancy check (CRC) is a technique used to detect errors in digital data. CRC is a hash function that detects accidental changes to raw computer data commonly used in digital telecommunications networks and storage devices such as hard disk drives. This technique was invented by W. Wesley Peterson in 1961 and further developed by the CCITT (Comité Consultatif International Telegraphique et Telephonique). Cyclic redundancy checks are quite simple to implement in hardware and can be easily analyzed mathematically. It is one of the better techniques in detecting common transmission errors. It is based on binary division and is also called polynomial code checksum. errors from devices including their IP address, Network Name, Device Name, Physical port name description, and type of diagnostics error, and value.

The type of errors that IntraVUE™ can detect for a port can be either CRChe cyclic redundancy check (CRC) is a technique used to detect errors in digital data. CRC is a hash function that detects accidental changes to raw computer data commonly used in digital telecommunications networks and storage devices such as hard disk drives. This technique was invented by W. Wesley Peterson in 1961 and further developed by the CCITT (Comité Consultatif International Telegraphique et Telephonique). Cyclic redundancy checks are quite simple to implement in hardware and can be easily analyzed mathematically. It is one of the better techniques in detecting common transmission errors. It is based on binary division and is also called polynomial code checksum. , In Errors, or input Errors are shown for devices supporting the standard MIB.

Port Descriptions (e.g. FastEthernet0/2) are displayed for connection lines.

Selecting the IP address of a device will center that device in the Topology View.

Types

The CRC is a polynomial function calculated and returned on the network frame as 4B number in Ethernet. Basically, it will catch all of the single bit errors and a good chunk of the double bit errors . It is meant to ensure that the frame was not corrupted in transit. So, if the CRC error counter increases for a specific uplink port (as in the picture above) it tells the user that the switches ran the polynomial function on the frames and the result was different from the 4B number found on the frame itself. Because of its nature, it this function is calculated on the OSI Layer 2.

 

In Errors (or CRC Errors) that indicate a bad FCSThe FCS is a mathematical way to ensure that all the frame's bits are correct without having the system examine each bit and compare it to the original. Packets with Alignment Errors also generate FCS Errors. and integral number of octets. These errors contain both FCS and Align Errors.

Frame Check Sequence (FCSThe FCS is a mathematical way to ensure that all the frame's bits are correct without having the system examine each bit and compare it to the original. Packets with Alignment Errors also generate FCS Errors.) errors indicates that frames received by an interface are an integral number of octets long but do not pass the FCS check.

 

CRC Align Errors indicate a bad FCS and a non-integral number of octects. An alignment error indicates a received frame with the number of bits received is an uneven byte count (that is, not an integral multiple of 8), and the frame has a Frame Check Sequence (FCSThe FCS is a mathematical way to ensure that all the frame's bits are correct without having the system examine each bit and compare it to the original. Packets with Alignment Errors also generate FCS Errors.) error. These errors are the result of OSI Layer 2 packet formation problems. Packets with Alignment Errors also generate FCS errors.

 

In general both of these types of CRC errors show when frames are corrupted at the OSI Layer 2 and indicate problems such as:

• Corruption or loss of data
• Duplex mismatch
• Faulty cabling
• Broken hardware
• End stations freezing
• Equipment power resetting
• Interface noise on network cabling segments (UTP, Copper, Fiber)
• Errors at the transmitting or receiving end

 

However, some level of CRC errors should be expected and it's acceptable according to the CRC standard, and a very low rate is still acceptable (i.e. not greater than 1 percent of the total network traffic).