Applies To:

Switch(es) – PowerConnect 62xx/8024/8024F 

Storage Platform(s) - Dell EqualLogic PS Series, Dell PowerVault MD32xxi/MD36xxi

Author:

Naveen Iyengar

Problem:

How to configure the recommended switch settings for IP-SAN?

Solution:

This article provides guidance on how to configure the recommended settings on the Dell PowerConnect switches for IP-SAN environments consisting of Dell EqualLogic or Dell PowerVault MD32xxi/MD36xxi iSCSI Storage arrays.

NOTE:

Dell strongly recommends using dedicated switches for iSCSI traffic.

PowerConnect 62xx/8024/8024F Switch Configuration

The switch must be placed in “privileged” mode to perform the recommended configuration steps. Use the following command to enter “privileged” mode:

console> enable
console#

NOTE:

One may be prompted for a password after submitting the enabled command.

The switch must be placed into configuration mode before any configuration steps can be performed. To enter configuration mode, the following command must be entered:

console# configure
console(config)#

The instructions in this article provide the Command Line Interface (CLI) commands for configuring a PowerConnect switch. Refer to Dell’s support website for the latest documentation if the web-interface is preferred.

 Interface Naming Convention

The conventions for naming interfaces on Dell PowerConnect 62xx/8024/8024F family of switches are as follows:

  • Unit#/Interface ID — each interface is identified by the Unit# followed by a / symbol and then the Interface ID (see below). For example, 2/g10 identifies gigabit port 10 within the second unit of a stack.
  • Unit# — the unit number is used only in a stacking solution where a number of switches are stacked to form a virtual device. In this case, the unit number identifies the physical device identifier within the stack.
  • Interface ID — is formed by the interface type followed by the interface number. There is currently a predefined list of interface types (see below). If additional interface types are to be defined, they must be registered with Dell. For example, 2/g10 identifies the gigabit port 10 on the second unit.
  • Interface Types — the following interface types are defined in the 62xx/8024/8024F series switches:
    • g — gigabit Ethernet port (for example, 1/g2 is the gigabit Ethernet port 2).
    • g — 10 Gigabit Ethernet port (for example, 1/xg2 is the 10 gigabit Ethernet port 2).

Enabling the PortFast Option to Configure Spanning-Tree Protocol (STP) Edge Ports

It is recommended that you disable spanning-tree protocol (STP) on the switch ports that connect end nodes (iSCSI initiators and storage array network interfaces). If you still decide to enable STP on those switch ports, then you should turn on the STP FastPort feature on the ports in order to allow immediate transition of the ports into a forwarding state. PortFast immediately transitions the port into STP forwarding mode upon linkup. The port still participates in STP. However, if the port is to be a part of the loop, the port eventually transitions into STP blocking mode. 

NOTE:

PowerConnect Switches default to RSTP (Rapid Spanning Tree Protocol) an evolution in STP that provides for faster Spanning tree convergence and is preferable to STP

To enable the Rapid Spanning Tree Protocol (RSTP):

console> enable
console# configure

console(config)# spanning-tree mode rstp

To enable PortFast, the spanning-tree PortFast command must be used. The following steps are an example of using this command to enable PortFast:

The following steps are an example of using this command to enable PortFast on a single port – Port 10 of PC8024 Switch #1 in a stack:

console> enable
console# configure
console(config)# interface ethernet 1/xg10
console(config-if-1/xg10)# spanning-tree portfast
console(config-if-1/xg10)# end
console# copy running-config startup-config
console# exit

The following steps are an example of how to enable PortFast on all ports in a PowerConnect 62xx/8024/8024F switch stack:

console> enable
console# configure
console(config)# interface range ethernet all
console(config-if)# spanning-tree portfast
console(config-if)# end
console# copy running-config startup-config
console# exit

Configuring Flow Control

Flow control on the PowerConnect 62xx Family of switches is off by default. To enable flow control on all ports in the switch, use the flowcontrol command.

NOTE:

Flow Control on the PowerConnect 8024/8024F switches are enabled by default

To enable flow control on all ports of a PowerConnect 6248, enter the following commands:

console> enable
console# configure
console(config)# flowcontrol
console(config)# exit
console# copy running-config startup-config
console# exit 

NOTE:

Dell PowerVault MD32xxi/MD36xxi and Dell EqualLogic  storage arrays will autoconfigure to the switch when Flow Control is turned on.

 Configuring Storm Control

A traffic “storm” occurs when a large outpouring of packets creates excessive network traffic that degrades network performance. Many switches have traffic storm control features that prevent ports from being disrupted by broadcast, multicast, or unicast traffic storms on physical interfaces. These features typically work by discarding network packets when the traffic on an interface reaches a percentage of the overall load (usually 80 percent, by default). 

Since iSCSI traffic is unicast traffic and can typically utilize the entire link, it is recommended that you disable unicast storm control on switches that handle iSCSI traffic in order to prevent any loss of packets. However, the use of broadcast and multicast storm control is encouraged.

The following steps are an example of using the commands to disable unicast and enable multicast/broadcast storm control on a single port – Port 10 of PC6248 Switch #3 in a stack:

console> enable
console# configure
console(config)# interface ethernet 3/g10
console(config-if-3/g10)# no storm-control unicast
console(config-if-3/g10)# storm-control multicast
console(config-if-3/g10)# storm-control broadcast
console(config-if-3/g10)# end
console# copy running-config startup-config
console# exit

The following steps are an example of how to configure the storm control on all ports in a PowerConnect 62xx/8024/8024F switch:

console> enable
console# configure
console(config)# interface range ethernet all
console(config-if)# no storm-control unicast
console(config-if)# storm-control multicast
console(config-if)# storm-control broadcast
console(config-if)# end
console# copy running-config startup-config
console# exit

 Configuring Jumbo Frames

Dell recommends that you enable jumbo frames on the switch ports that handle iSCSI traffic. Jumbo frames are not enabled by default. To enable jumbo frames on the Powerconnect 62xx/8024/8024F switch, use the MTU interface configuration command with a parameter of 9216.

The following steps are an example of using the commands to enable the jumbo frame on one specific port – Port 10 of PC8024 Switch #1 in a stack:

console> enable
console# configure
console(config)# interface ethernet 1/xg1
console(config-if-1/xg1)# mtu 9216
console(config-if-1/xg1)# end
console# copy running-config startup-config
console# exit

The following steps are an example of how to configure the jumbo frame on all ports in a PowerConnect 62xx/8024/8024F switch:

console> enable
console# configure
console(config)# interface range ethernet all
console(config-if)# mtu 9216
console(config-if)# end
console# copy running-config startup-config
console# exit

NOTE:

Jumbo frames must be enabled throughout the entire iSCSI SAN from the NICs, Switches, and storage array ports, otherwise, behavior may be inconsistent.

 

NOTE:

If jumbo frames are correctly enabled throughout the iSCSI SAN fabric then Dell PowerVault MD32xxi/MD36xxi and Dell EqualLogic storage arrays will autoconfigure to handle jumbo frames. As a result, no jumbo frame configuration is required to be done on these storage arrays.

 Configuring Link Aggregated Group (LAG)

When you have two or more Ethernet switches for iSCSI traffic it is recommended to a create Link Aggregated Group (LAG) by having Interswitch Links (ISLs) for redundancy, performance and better scalability.

The number of connections or Ethernet ports in the LAG per switch should ideally be equal to the number of active Ethernet interfaces on all iSCSI storage arrays connected to the switch. For example, if you have two switches connected to two arrays, and each switch has two active array network connections, the LAG should ideally be an aggregate of at least four Ethernet ports.

 

NOTE:

  A stacking bus is strongly recommeneded if a large number of available ports will be used for the LAG or the available ports are at a premium.

The following steps are an example of how to configure the LAG that consists of four ports – ports 21-24 that are linked between two PowerConnect 8024 switches. It is required to enable the jumbo frames on the LAG.

 Switch 1:

console> enable
console# configure
console(config)# interface range ethernet 1/xg21-1/xg24
console(config-if)# channel-group 1 mode on
console(config-if)# mtu 9216
console(config-if)# exit
console(config)# interface port-channel 1
console(config-if-ch1)# mtu 9216
console(config-if-ch1)# end
console# copy running-config startup-config
console# exit

 

Switch 2:

console> enable
console# configure
console(config)# interface range ethernet 1/xg21-1/xg24
console(config-if)# channel-group 1 mode on
console(config-if)# mtu 9216
console(config-if)# exit
console(config)# interface port-channel 1
console(config-if-ch1)# mtu 9216
console(config-if-ch1)# end
console# copy running-config startup-config
console# exit

References: