Design Reference

10/100/1000BASE-TX Auto-Negotiation recommendations
Auto-Negotiation lets devices share a link and automatically configures both devices so that they
take maximum advantage of their abilities. Auto-Negotiation uses a modified 10BASE-T link integrity
test pulse sequence to determine device ability.
The Auto-Negotiation feature allows the devices to switch between the various operational modes in
an ordered fashion and allows management to select a specific operational mode. The Auto-
Negotiation feature also provides a parallel detection (also called autosensing) function to allow the
recognition of 10BASE-T, 100BASE-TX, 100BASE-T4, and 1000BASE-TX compatible devices,
even if they do not support Auto-Negotiation. In this case, only the link speed is sensed; not the
duplex mode. Avaya recommends the Auto-Negotiation configuration as shown in the following
table, where A and B are two Ethernet devices.
Table 13: Recommended Auto-Negotiation configuration on 10/100/1000BASE-TX ports
Port on A Port on B Remarks Recommendations
Auto-Negotiation
enabled
Auto-Negotiation
enabled
Ports negotiate on highest
supported mode on both
sides.
Avaya recommends that
you use this configuration if
both ports support Auto-
Negotiation mode.
Full-duplex Full-duplex Both sides require the same
mode.
Avaya recommends that
you use this configuration if
you require full-duplex, but
the configuration does not
support Auto-Negotiation.
Auto-Negotiation cannot detect the identities of neighbors or shut down misconnected ports. Upper-
layer protocols perform these functions.
Auto MDIX
Automatic medium-dependent interface crossover (Auto-MDIX) automatically detects the need for a
straight-through or crossover cable connection and configures the connection appropriately. This
removes the need for crossover cables to interconnect switches and ensures either type of cable
can be used. The speed and duplex setting of an interface must be set to Auto for Auto-MDIX to
operate correctly.
CANA
Use Custom Auto-Negotiation Advertisement (CANA) to control the speed and duplex settings that
the interface modules advertise during Auto-Negotiation sessions between Ethernet devices.
Hardware fundamentals and guidelines
32 Network Design Reference for Avaya VSP 4000 Series December 2014
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