Technical data

Switching and Routing
May 2012 © 2012 Brocade Communications Systems, Inc. 2 - 49
Figure 2.7 Multi-slot aggregate link
By default, the device’s ports are divided into 4-port groups. The software dynamically assigns a unique key to
each 4-port group. If you need to divide a 4-port group into two 2-port groups, change the key in one of the groups
so that the two 2-port groups have different keys. For example, if you plan to use ports 1/1 and 1/2 in VLAN 1, and
ports 1/3 and 1/4 in VLAN 2, change the key for ports 1/3 and 1/4.
NOTE: If you change the key for a port group, Brocade recommends that you use the value 10000 or higher, to
avoid potential conflicts with dynamically created keys.
About Blocked Ports
Brocade devices can block traffic on a port or shut down a port that is part of a trunk group or aggregate link for
the following reasons:
• For the purpose of link aggregation, the ports on Brocade devices are grouped into pairs of two; one odd-
numbered port, and the next even-numbered port. When you configure link aggregation on a port (for
instance, on an odd-numbered port), this port will be blocked and unable to join a trunk group until you
configure the adjacent port (the even-numbered port) as part of the aggregate link. When you configure both
ports with link aggregation and assign both ports the same key, both ports are able to join a trunk group.
Once the ports become part of a trunk group, they can transmit and receive LACP packets.
NOTE: Ports that are configured as part of an aggregate link must also have the same key. For more information
about assigning keys, see the “Link Aggregation Parameters” on page 2-47
• When a port joins a trunk group and the port on the other end of the link shuts down or stops transmitting
LACP packets, the Brocade device blocks the port. Depending on the timeout value set on the port, the link
aggregation information expires.
If either of these events occur, the Brocade device shuts down the port and notifies all the upper layer protocols
that the port is down.
Brocade devices can also block traffic on a port that is initially configured with link aggregation. The port is
blocked until it joins a trunk group. In this case, traffic is blocked, but the port is still operational.
A port remains blocked until one of the following events occur:
• Link aggregation is enabled on the adjacent port (the paired port) and both ports have the same key
• LACP brings the port back up
• The port joins a trunk group
All ports in a multi-slot
aggregate link have
the same key.
Port 1/2
Port 1/4
Port 1/1
Port 3/6
Port 1/3
Port 3/7
Port 3/8
Port 3/5
System ID: aaaa.bbbb.cccc
Ports 1/1 - 1/4: Key 0
Ports 3/5 - 3/8: Key 0