20. Link Aggregation
ROX™ v2.2 User Guide
193
RuggedBackbone™ RX5000
• If one of the aggregated ports joins or leaves a multicast group (for example, via IGMP or GMRP),
all other ports in the trunk also join or leave.
• Any port configuration parameter changes, such as VLAN or CoS, are automatically applied to all
ports in the trunk.
• Secondary port configuration and status parameters are not be shown in configuration and status
sessions in the user interface. Secondary port numbers are simply listed next to the primary port
number in the user interface.
• When a secondary port is added to a port trunk, it inherits all of the configuration settings of the
primary port. When the secondary port is removed from the port trunk, the settings it had prior to
the aggregation are restored.
• Physical layer features, such as physical link configuration, link status, rate limiting, and Ethernet
statistics, still treat each aggregated port separately.
• Physical configuration and status parameters are not automatically applied to other ports in the
trunk and are displayed for each port as usual.
• Ensure that only ports with the same speed and duplex settings are aggregated. If auto-negotiation
is used, ensure that it is resolved to the same speed for all ports in the port trunk.
• To determine the value of the Ethernet statistics counter for the port trunk, add the values of the
counters for all of the ports in the port trunk.
20.1.2. Link Aggregation Limitations
• A port mirroring target port cannot be a member of a port trunk. However, a port mirroring source
port can be a member of a port trunk.
• A DHCP Relay Agent Client port cannot be a member of a port trunk.
• Load balancing between the links of a bundle is randomized and may not be ideal. For example, if
three 100Mbs links are aggregated, the resulting bandwidth of the port trunk may not be precisely
300Mbs.
• A Static MAC Address should not be configured to reside on an aggregated port, as it may cause
some frames destined for that address to be dropped.
• A secure port cannot be a member of a port trunk.
The port trunk must be properly configured on both sides of the aggregated link. In switch-
to-switch connections, if the configuration of both sides does not match (for example, some
ports are mistakenly not included in the port trunk), the configuration results in a loop. The
following procedure is strongly recommended to configure a port trunk:
1.
Disconnect or disable all the ports involved in the configuration. That is, disconnect or
disable all ports that are being added to or removed from the port trunk.
2.
Configure the port trunk on both switches.
3.
Double-check the port trunk configuration on both switches.
4.
Reconnect or re-enable the ports.
If the port trunk is configured while the ports are not disconnected or disabled, the port will
be automatically disabled for a few seconds.
The IEEE 802.3ad Link Aggregation standard requires all physical links in the port trunk
to run at the same speed and in full-duplex mode. If this requirement is violated, the
performance of the port trunk will drop.
