Dell Brocade G620 Brocade 8.0.1 Fabric OS Administratiors Guide - Page 470

Recommendations for trunk groups

Page 470 highlights

Managing Trunking Connections ∙ All of the ports in a trunk group must belong to the same port group. ∙ All of the ports in a trunk group must meet the following conditions: - They must be running at the same speed. - They must be configured for the same distance. - They must have the same QoS and FEC state. - They must have the same encryption and compression state. ∙ Trunk groups must be between Brocade switches (or Brocade adapters in the case of F_Port trunking). ∙ There must be a direct connection between participating switches. ∙ Trunking cannot be done if ports are in ISL R_RDY mode. (You can disable this mode by using the portCfgIslMode command.) ∙ Trunking is supported only on FC ports. Virtual FC ports (VE_Ports or VEX_Ports) do not support trunking. Recommendations for trunk groups To identify the most useful trunk groups, consider the following recommendations along with the standard guidelines for SAN design: ∙ Evaluate the traffic patterns within the fabric. ∙ Place trunking-capable switches adjacent to each other. This maximizes the number of trunk groups that can form. If you are using a core and edge topology, place trunking-capable switches at the core of the fabric and any switches that are not trunking-capable at the edge of the fabric. ∙ When connecting two switches with two or more ISLs, ensure that all trunking requirements are met to allow a trunk group to form. ∙ Determine the optimal number of trunk groups between each set of linked switches, depending on traffic patterns and port availability. The goal is to avoid traffic congestion without unnecessarily using ports that could be used to attach other switches or devices. ∙ Each physical ISL uses two ports that could otherwise be used to attach node devices or other switches. ∙ Trunk groups can be used to resolve ISL oversubscription if the total capability of the trunk group is not exceeded. ∙ Consider how the addition of a new path will affect existing traffic patterns: - A trunk group has the same link cost as the master ISL of the group, regardless of the number of ISLs in the group. This allows slave ISLs to be added or removed without causing data to be rerouted, because the link cost remains constant. - The addition of a path that is shorter than existing paths causes traffic to be rerouted through that path. - The addition of a path that is longer than existing paths may not be useful, because the traffic will choose the shorter paths first. ∙ Plan for future bandwidth addition to accommodate increased traffic. For trunk groups over which traffic is likely to increase as business requirements grow, consider leaving one or two ports in the group available for the future nondisruptive addition of bandwidth. ∙ Consider creating redundant trunk groups where additional ports are available or paths are particularly critical. This helps to protect against oversubscription of trunk groups, multiple ISL failures in the same group, and the rare occurrence of an ASIC failure. ∙ To provide the highest level of reliability, deploy trunk groups in redundant fabrics to help ensure that ISL failures do not disrupt business operations. Brocade Fabric OS Administration Guide, 8.0.1 470 53-1004111-02

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All of the ports in a trunk group must belong to the same port group.
All of the ports in a trunk group must meet the following conditions:
They must be running at the same speed.
They must be configured for the same distance.
They must have the same QoS and FEC state.
They must have the same encryption and compression state.
Trunk groups must be between Brocade switches (or Brocade adapters in the case of F_Port trunking).
There must be a direct connection between participating switches.
Trunking cannot be done if ports are in ISL R_RDY mode. (You can disable this mode by using the
portCfgIslMode
command.)
Trunking is supported only on FC ports. Virtual FC ports (VE_Ports or VEX_Ports) do not support trunking.
Recommendations for trunk groups
To identify the most useful trunk groups, consider the following recommendations along with the standard guidelines for SAN design:
Evaluate the traffic patterns within the fabric.
Place trunking-capable switches adjacent to each other.
This maximizes the number of trunk groups that can form. If you are using a core and edge topology, place trunking-capable
switches at the core of the fabric and any switches that are not trunking-capable at the edge of the fabric.
When connecting two switches with two or more ISLs, ensure that all trunking requirements are met to allow a trunk group to
form.
Determine the optimal number of trunk groups between each set of linked switches, depending on traffic patterns and port
availability.
The goal is to avoid traffic congestion without unnecessarily using ports that could be used to attach other switches or devices.
Each physical ISL uses two ports that could otherwise be used to attach node devices or other switches.
Trunk groups can be used to resolve ISL oversubscription if the total capability of the trunk group is not exceeded.
Consider how the addition of a new path will affect existing traffic patterns:
A trunk group has the same link cost as the master ISL of the group, regardless of the number of ISLs in the group. This
allows slave ISLs to be added or removed without causing data to be rerouted, because the link cost remains constant.
The addition of a path that is shorter than existing paths causes traffic to be rerouted through that path.
The addition of a path that is longer than existing paths may not be useful, because the traffic will choose the shorter paths
first.
Plan for future bandwidth addition to accommodate increased traffic.
For trunk groups over which traffic is likely to increase as business requirements grow, consider leaving one or two ports in the
group available for the future nondisruptive addition of bandwidth.
Consider creating redundant trunk groups where additional ports are available or paths are particularly critical.
This helps to protect against oversubscription of trunk groups, multiple ISL failures in the same group, and the rare occurrence
of an ASIC failure.
To provide the highest level of reliability, deploy trunk groups in redundant fabrics to help ensure that ISL failures do not disrupt
business operations.
Managing Trunking Connections
Brocade Fabric OS Administration Guide, 8.0.1
470
53-1004111-02