Brocade TurboIron 24X Series Configuration Guide - Manual (Page 381)

Brocade TurboIron 24X Series Configuration Guide 347
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Dynamic link aggregation
• If the feature places a port into a trunk group as a secondary port, all configuration information
except information related to link aggregation is removed from the port. For example, if port 3
has an IP interface, and the link aggregation feature places port 3 into a trunk group consisting
of ports 1 – 4, the IP interface is removed from the port.
NOTE
Unique Key should be configured for each group of ports that have differing VLAN membership,
regardless of being tagged or untagged.
• If you use this feature on a Layer 3 Switch that is running OSPF or BGP4, the feature causes
these protocols to reset when a dynamic link change occurs. The reset includes ending and
restarting neighbor sessions with OSPF and BGP4 peers, and clearing and relearning dynamic
route entries and forwarding cache entries. Although the reset causes a brief interruption, the
protocols automatically resume normal operation.
• You can enable link aggregation on 802.1Q tagged ports (ports that belong to more than one
port-based VLAN).
NOTE
It is recommended to disable the link aggregation on ports before you disable link aggregation.
Adaptation to trunk disappearance
The device will tear down an aggregate link if the device at the other end of the link reboots or
brings all the links down. Tearing the aggregate link down prevents a mismatch if the other device
has a different trunk configuration following the reboot or re-establishment of the links. Once the
other device recovers, 802.3 can renegotiate the link without a mismatch.
Flexible trunk eligibility
The criteria for trunk port eligibility in an aggregate link are flexible. A range of ports can contain
down ports and still be eligible to become an aggregate link.
It also increases the tolerance for down ports during link negotiation. In previous releases, all the
ports in a valid trunk configuration (2-port, 4-port, or 8-port trunk starting on a valid primary port
number) need to be up.
The device places the ports into 2-port groups by default, consisting of an odd-numbered port and
the next even-numbered port. For example, ports 1 and 2 are a two-port group, as are ports 3 and
4, and so on. If either of the ports in a two-port group is up, the device considers both ports to be
eligible to be in an aggregate link.
Figure 32 shows an example of 2-port groups in a range of four ports on which link aggregation is
enabled. Based on the states of the ports, some or all of them will be eligible to be used in an
aggregate link.
FIGURE 32 Two-port groups used to determine aggregation eligibility