McAfee M4050 Troubleshooting Guide - Page 30

Auto-negotiation, Inter-Switch Link Protocol ISL configuration

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McAfee® Network Security Platform 6.0 Troubleshooting Network Security Platform Counter Description Possible Causes Late Collisions A late collision occurs when two This is an indication of faulty hardware (NIC, devices transmit at the same time cable, or switch port) or a duplex mismatch. and neither side of the connection detects a collision. The reason for this occurrence is that the time to propagate the signal from one end of the network to another is longer than the time to put the entire packet on the network. The two devices that cause the late collision never see that the other is sending until after it puts the entire packet on the network. Late collisions are detected by the transmitter after the first time slot of the 64-byte transmit time occurs. They are only detected during transmissions of packets longer than 64 bytes. Its detection is exactly the same as it is for a normal collision; it just happens later than it does for a normal collision. Excessive Collisions Excessive collisions are the number This is an indication of over utilization of the of frames that are dropped after 16 switch port at half-duplex or duplex mismatch. attempts to send the packet resulted in 16 collisions. Carrier Sense Carrier sense occurs every time an This is an indication of faulty hardware (NIC, Ethernet controller wants to send cable, or switch port). data and the counter is incremented when there is an error in the process. Runts These are frames smaller than 64 bytes with a bad FCS value. This is an indication of the result of collisions, duplex mismatch, IEEE 802.1Q (dot1q), or an Inter-Switch Link Protocol (ISL) configuration issue. Giants These are frames that are greater than 1518 bytes and have a bad FCS value. This is an indication of faulty hardware, dot1q, or an ISL configuration issue. Auto-negotiation Auto-negotiation issues typically do not result in link establishment issues. Instead, autonegotiation issues mainly result in a loss of performance. When auto-negotiation leaves one end of the link in, for example, full-duplex mode and the other in half-duplex (also known as a duplex mismatch), errors and retransmissions can cause unpredictable behavior in the network causing performance issues, intermittent connectivity, and loss of communication. Generally these errors are not fatal-traffic still makes it through-but locating and fixing them is a time-waster. 21

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McAfee® Network Security Platform 6.0
Troubleshooting Network Security Platform
21
Counter
Description
Possible Causes
Late Collisions
A late collision occurs when two
devices transmit at the same time
and neither side of the connection
detects a collision. The reason for
this occurrence is that the time to
propagate the signal from one end
of the network to another is longer
than the time to put the entire
packet on the network. The two
devices that cause the late collision
never see that the other is sending
until after it puts the entire packet on
the network. Late collisions are
detected by the transmitter after the
first time slot of the 64-byte transmit
time occurs. They are only detected
during transmissions of packets
longer than 64 bytes. Its detection is
exactly the same as it is for a
normal collision; it just happens later
than it does for a normal collision.
This is an indication of faulty hardware (NIC,
cable, or switch port) or a duplex mismatch.
Excessive
Collisions
Excessive collisions are the number
of frames that are dropped after 16
attempts to send the packet resulted
in 16 collisions.
This is an indication of over utilization of the
switch port at half-duplex or duplex mismatch.
Carrier Sense
Carrier sense occurs every time an
Ethernet controller wants to send
data and the counter is incremented
when there is an error in the
process.
This is an indication of faulty hardware (NIC,
cable, or switch port).
Runts
These are frames smaller than 64
bytes with a bad FCS value.
This is an indication of the result of collisions,
duplex mismatch, IEEE 802.1Q (dot1q), or an
Inter-Switch Link Protocol (ISL) configuration
issue.
Giants
These are frames that are greater
than 1518 bytes and have a bad
FCS value.
This is an indication of faulty hardware, dot1q, or
an ISL configuration issue.
Auto-negotiation
Auto-negotiation issues typically do not result in link establishment issues. Instead, auto-
negotiation issues mainly result in a loss of performance. When auto-negotiation leaves
one end of the link in, for example, full-duplex mode and the other in half-duplex (also
known as a duplex mismatch), errors and retransmissions can cause unpredictable
behavior in the network causing performance issues, intermittent connectivity, and loss of
communication. Generally these errors are not fatal-traffic still makes it through-but
locating and fixing them is a time-waster.