Dell 5316M User Manual

Link Aggregation Interoperability
of the Dell™ PowerConnect™
5316M with Cisco IOS or Cisco
CatOS based Switches

By Bruce Holmes

August 2005

Contents

Introduction................................................................................................................................................3

Link Aggregation with Gigabit Ethernet Cisco Switches.................................................................. 5

Configuring the PowerConnect 5316M external ports for Dynamic Link Aggregation...............6

Configuring a Cisco IOS Gigabit Ethernet Switch for Dynamic Link Aggregation.....................6

Configuring a Cisco CATOS Gigabit Ethernet Switch for Dynamic Link Aggregation .............7

Confirming a successful Dynamic Link Aggregation connection with the PowerConnect

5316M...........................................................................................................................................................7

Confirming a successful Dynamic Link Aggregation connection with Cisco IOS.......................7

Confirming a successful Dynamic Link Aggregation connection with CISCO CATOS............. 8

Configuring the PowerConnect 5316M external ports for Static Link Aggregation..................... 9

Configuring a CISCO IOS Switch for Static Link Aggregation.......................................................9

Configuring a Cisco CATOS Switch for Static Link Aggregation...................................................9

Confirming a successful Static Link Aggregation connection........................................................10

Link aggregation with Cisco Fast Ethernet Switches........................................................................11

Configuration Limitations..................................................................................................................... 12

Port configuration differences with Dell and CISCO ......................................................................13

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Introduction

The Dell PowerConnect 5316M is a fully managed Layer 2 switch that helps organizations reduce
the price and cable sprawl traditionally associated with the networking of servers. This robust
networking switch is based on the same technology as the PowerConnect 5324, but is housed in a
different form factor that is specifically designed for the Dell Modular Server Enclosure.

Many IT organizations have great investments in a standardized core network infrastructure as
well as the human resources to maintain that network. With this investment in mind, Dell has
designed the PowerConnect 5316M based on industry standard network protocols to ensure
interoperability whenever possible.

Figure 1 – PowerConnect 5316M configuration options

Dell PowerEdge 1855

Blade Server (top view)

Optional Intel Gigabit

Ethernet daughtercard

PowerConnect 5316M

The Dell Modular Server Enclosure can support one to four PowerConnect 5316M switch modules.
Modules in chassis I/O bays 1 and 2 connect to the embedded Ethernet controllers on the blade
(population of I/O bay 1 is required; population of I/O bay 2 is optional). Additionally, chassis I/O
bays 3 and 4 can also be populated if optional dual port GbE daughtercards are installed in the
blade servers.

This paper describes how to configure the Dell PowerConnect™ 5316M Gigabit Ethernet switch to
interoperate and connect with Cisco IOS
standard link aggregation groups (LAGs) that adhere to the IEE 802.3ad standard. Both static and
dynamic LAGs are discussed.

The table below shows some of the terms used to refer to LAGs in Dell and Cisco documentation.
This paper will use the term LAG.

Dell Modular Server Enclosure

(rear view)

2

and CatOS3 based switches when using industry

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Dell PowerConnect Cisco IOS/Cat OS

Link Aggregation
Groups (LAGs)

EtherChannel

Fast EtherChannel (FEC)
Gigabit EtherChannel
(GEC)

port-channel Channeling

channel-group channel-group

The primary purpose of LAGs is to increase the overall bandwidth between two switches. This is
accomplished by effectively aggregating multiple ports together that act as a single, logical
connection between the two switches.

The IEEE 802.3ad standard based link aggregation implemented on the PowerConnect 5316M is
interoperable with Cisco Ether Channel using both static and dynamic configuration (dynamic via
LACP not the Cisco proprietary PAgP). Dell is a member of the University of New Hampshire
Interoperability Lab, where all PowerConnect products are tested to confirm interoperability with
other Consortium members. Included in these tests is link aggregation interoperability with other
Consortium members. Additional information regarding UNH’s link aggregation testing can be
found at:

ftp://ftp.iol.unh.edu/pub/bfc/testsuites/la.io.test.suite.pdf

Link aggregation can be configured as either dynamic or static. Dynamic configuration is
supported using the IEEE 802.3ad standard, which is known as Link Aggregation Control Protocol
(LACP). Static configuration is used when connecting the Dell PowerConnect 5316M Gigabit
Ethernet switch to an external Gigabit Ethernet switch that does not support LACP. One advantage
of LACP is that the protocol enables the Gigabit Ethernet switch to confirm that the external switch
is also configured for link aggregation. When using static configuration, a cabling or configuration
mistake involving the Dell PowerConnect 5316M or the external switch could go undetected and
thus can cause undesirable network behavior. Both static and dynamic LAGs (via LACP) can
detect physical link failures within the LAG and continue forwarding traffic through the other
connected links within that same LAG. LACP can also detect switch or port failures that do not
result in loss of link. This provides a more resilient LAG. Best practices suggest using dynamic
link aggregation instead of static link aggregation.

The examples shown below use the switches’ command line interfaces to configure the switches.
See the Dell™ PowerConnect™ 5316M Command Line Interface (CLI) Guide for more detailed
information. See the section “Port Channel Commands” for information on configuring LAGs via
the CLI.

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If desired, any of the example configurations can be performed on the Dell PowerConnect 5316M
via the web based interface (WBI) as well. See the Dell PowerConnect 5316M Ethernet Switch Module
Userʹs Guide for a description of the Dell WBI. See the section “Defining LAG Parameters” for
information on configuring LAGs via the WBI. The Dell™ PowerConnect™ 5316M Command Line
Interface (CLI) Guide and the Dell PowerConnect 5316M Ethernet Switch Module Userʹs Guide are
located on the dell support website:

http://support.dell.com/support/edocs/network/PC5316M/en/index.htm.

Link Aggregation with Gigabit Ethernet Cisco Switches

The following examples show minimal configurations necessary to establish a LAG between a
Cisco IOS Gigabit Ethernet switch (Catalyst 3750), Cisco CatOS Ethernet switch (Catalyst 6509) and
the Dell PowerConnect 5316M. These commands work without issue when starting from a default
configuration of the switches.

To set the Dell PowerConnect 5316M to default configuration, use the following commands:

NOTE: This will erase any configuration data previously configured and reboot the switch.

5316M# delete startup-config
5316M# reload

To set a Cisco IOS based switch to default configuration, use the following commands:

NOTE: This will erase any configuration data previously configured and reboot the switch.

3750# delete flash:/config.text
3750# reload

To set a Cisco CatOS based switch (e.g. Catalyst 6509) to default configuration, use the following
commands:

NOTE: This will erase any configuration data previously configured and reboot the switch.

Cat_6509 (enable) clear config all

Please see other sections of this paper for cases when it is impractical to reset the switches to factory
defaults.

The Dell PowerConnect 5316M can support up to 8 different LAGs. A port channel can have from
zero to six of the external ports as members. Internal ports can not be members of a LAG. The
examples in this document show different numbers of ports in a LAG.

It is recommended that the ports to be aggregated on both the Cisco and Dell switches be
disconnected during configuration. This will avoid any network loops being formed before the
LAGs are set up.

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