Configuration Guide User guide

722 FastIron Configuration Guide
53-1002494-02
Dynamic link aggregation
FastIron X Series devices
The following notes and feature limitations apply to the FastIron X Series devices:
You cannot use 802.3ad link aggregation on a port configured as a member of a static trunk
group.
The dynamic link aggregation (802.3ad) implementation on FastIron X Series devices allows
different numbers of ports to be aggregated in a link, depending on the IP version (IPv6 or
IPv4) and the software version running on the device. For details, refer to Table 132 on
page 699.
The default key assigned to an aggregate link is based on the port type (1 Gbps port or 10
Gbps port). The Brocade device assigns different keys to 10 Gbps ports than to 1 Gbps ports
so that ports with different physical capabilities will not be able to form a trunk.
NOTE
The trunks that will be formed by link aggregation will strictly adhere to the static trunking rules
on the Brocade device. Be careful in selecting keys if you are manually configuring link
aggregation keys. Make sure that the possible trunks that you expect to be formed conform to
the static trunking rules.
When the FastIron X Series device dynamically adds or changes a trunk group, the show trunk
command displays the trunk as both configured and active. However, the show running-config
or write terminal command does not contain a trunk command defining the new or changed
trunk group.
If the FastIron X Series device 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 1/3 has an IP interface, and the link aggregation feature places port
1/3 into a trunk group consisting of ports 1/1 through 1/4, the IP interface is removed from
the port.
If the FastIron X Series device (Layer 3) is running OSPF or BGP4, the device 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), as well as on untagged ports.
Adaptation to trunk disappearance
The Brocade 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, dynamic link aggregation can renegotiate the link without a
mismatch.