Brocade MLX Series and Brocade NetIron XMR Diagnostic Guide ...

Link fault signaling 3A CRC alignment error is generated when the total number of packets received is from 64through 1518 octets, but contains either a bad FCS with an integral number of octets (FCSError) or a bad FCS with a non-integral number of octets (Alignment Error).• RuntsAny received packet that is less than 64 bytes is illegal, and is called a runt. In most cases,runts arise from a collision, and although they indicate an illegal reception, they may occur oncorrectly functioning networks. The receiving Brocade device discards all runt frames.• GiantsAny received packet that is greater than the maximum frame size is called a giant. In theory,the jabber control circuit in the transceiver must prevent any node from generating such aframe, but certain failures in the physical layer may also give rise to oversized Ethernet frames.Like runts, giants are discarded by the receiving Brocade device.• Misaligned framesAny frame that does not contain an integral number of received octets (bytes) is also illegal. Areceiver has no way of knowing which bits are legal, and how to compute the CRC-32 of theframe. Such frames are therefore also discarded by the Ethernet receiver.• Old software versionsFeature issues are often caused because the device is running an old version of the software.Brocade recommends that you always update software to reflect the latest patches andversions. If you have questions about your software version, contact Brocade TechnicalSupport for assistance.Link fault signalingLink fault signaling (LFS) is a physical layer protocol that enables communication on a link betweentwo 10 Gigabit Ethernet devices. When LFS is configured on a Brocade 10 Gigabit Ethernet port,the port can detect and report fault conditions on transmit and receive ports. Brocade IronWaresoftware supports LFS among all 10 Gigabit Ethernet devices, including LFS support between Firstand Second generation devices. LFS is disabled by default on 10 Gbps interfaces.When LFS is enabled on an interface, the following syslog messages are generated whenever theinterface goes up or down, or when the TX or RX fiber is removed from both sides of a link whereLFS is configured.interface ethernet1/1, state down - link downinterface ethernet1/1, state upAfter the fiber is installed, the Link and Activity LEDs on the module light up when traffic is flowingacross the link.NOTELFS is disabled by default on 10 Gbps interfaces. It is enabled by default (and cannot be disabled)on 1 Gpbs interfaces.Brocade MLX Series and Brocade NetIron XMR Diagnostic Guide 6153-1002426-02