NAD 3020 User Manual 2

Integrating the Cisco Catalyst Blade

Switch 3020 for the HP c-Class

BladeSystem into the Cisco Data

Center Network Architecture

Design Guide

Contents

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

HP c-Class BladeSystem Enclosure Overview............................................................................. 3

Cisco Catalyst Blade Switch 3020 for HP...................................................................................... 5

Cisco Catalyst Blade Switch 3020 Features ................................................................................. 6

Spanning Tree.............................................................................................................................. 6

Traffic Monitoring.......................................................................................................................... 8

Link Aggregation Protocols........................................................................................................... 9

Data Center Network Architecture............................................................................................... 10

Data Center Network Components............................................................................................. 10

Aggregation Layer ......................................................................................................................11

Access Layer.............................................................................................................................. 11

High Availability ..........................................................................................................................12

Design Goals.............................................................................................................................. 12

High Availability ..........................................................................................................................12

High Availability for the BladeSystem Switching Infrastructure .............................................. 13

High Availability for the Blade Servers ................................................................................... 13

Scalability ................................................................................................................................... 14

Physical Port Count ............................................................................................................... 14

Slot Count .............................................................................................................................. 15

Management .............................................................................................................................. 16

Out-of-Band Management ..................................................................................................... 16

In-Band Management ............................................................................................................ 17

Serial Console Port................................................................................................................ 17

Management Options............................................................................................................. 18

HP c-Class BladeSystem iLO Connectivity............................................................................ 18

Design and Implementation Details............................................................................................. 18

Network Management Recommendations.................................................................................. 18

Network Topologies Using the Cisco Catalyst Blade Switch 3020 .............................................19

Recommended Topology....................................................................................................... 19

Alternative Topology .............................................................................................................. 22

Configuration Details .................................................................................................................. 23

VLAN Configuration ............................................................................................................... 24

RPVST+ Configuration .......................................................................................................... 24

Inter-Switch Link Configuration .............................................................................................. 24

Server-Port Configuration ...................................................................................................... 26

Server Default Gateway Configuration................................................................................... 27

RSPAN Configuration ............................................................................................................ 28

Design Guide

Introduction

This guide provides best design practices for deploying the Cisco® Catalyst® Blade

Switch 3020 for the HP c-Class BladeSystem enclosure within the Cisco Data Center

Networking Architecture. It describes the internal components of the blade-server

enclosure and Cisco Catalyst Blade Switch 3020 and explores different methods of

deployment.

HP c-Class BladeSystem Enclosure Overview

The HP c-Class BladeSystem enclosure represents the next generation of blade-server and blade-

switch integration. Figure 1 shows both a front and back side view of the cabinet. The c-Class

enclosure can hold up to 16 half-height servers and up to 8 switch modules. The servers are

available with either Intel or AMD processors. HP also offers full-height servers with two Intel

processors. Both support dual-core processors. The first two switch bays must contain Ethernet

switches because the onboard LAN adapters are routed to those bays. The additional six bays are

available for additional Ethernet switches, Fibre Channel switches, InfiniBand switches, or copper

or fiber pass-through modules. Each full-height server contains four Gigabit Ethernet interfaces,

two running each module in module slots 1 and 2. Full-height servers also have three mezzanine

slots for additional I/O connections such as Fibre Channel, InfiniBand, or even more Ethernet

switches.

Figure 1. Front and Back Views of HP c-Class BladeSystem Enclosure

The HP c-Class BladeSystem backplane provides power and network connectivity to the blades.

The base I/O module slots house a pair of Cisco Catalyst Blade Switch 3020s, which provide a

highly available and multihomed environment wherein each server blade is attached through a

Gigabit Ethernet port to each Cisco Catalyst Blade Switch 3020. Two Cisco Catalyst Blade Switch

3020s within the blade enclosure connect the blade-server modules to external network devices

such as aggregation layer switches. Figures 2 and 3 show the logical connections between the

servers, the two internal blade switches, and the outside network.

Figure 2. Enclosure Interconnections Using Full-Height Servers

Design Guide

Figure 3. Enclosure Interconnections Using Half-Height Servers

Design Guide

Cisco Catalyst Blade Switch 3020 for HP

This section briefly describes the Cisco Catalyst Blade Switch 3020 for HP and explains how the

blade servers within the HP c-Class BladeSystem are physically connected to the switching

modules.

The Cisco Catalyst Blade Switch 3020 provides enhanced Layer 2 services (known as Layer 2+ or

Intelligent Ethernet switching) to the HP c-Class BladeSystem. The Cisco Catalyst Blade Switch

3020 enhances basic Layer 2 switching by including Cisco proprietary protocols, access control

lists (ACLs), and quality of service (QoS) based on Layer 3 information. With Simple Network

Management Protocol (SNMP), command-line interface (CLI), or HTTP management options

available and a robust set of Cisco IOS

Switch 3020 naturally integrates into the data center environment. The following features highlight

this capacity:

●

Loop protection and rapid convergence with support for Per VLAN Spanning Tree Plus

(PVST+), IEEE 802.1w, IEEE 802.1s, Bridge Protocol Data Unit (BDPU) Guard, Loop

Guard, PortFast, UplinkFast, and Unidirectional Link Detection (UDLD)

●

Advanced management protocols, including Cisco Discovery Protocol, VLAN Trunking

Protocol (VTP), and Dynamic Trunking Protocol (DTP)

●

Port Aggregation Protocol (PAgP) and Link Aggregation Control Protocol (LACP) for link

load balancing and high availability

●

Support for authentication services, including RADIUS and TACACS+ client support

●

Support for protection mechanisms, such as limiting the number of MAC addresses allowed

or shutting down the port in response to security violations

Each Ethernet switch provides eight external Ethernet ports for connecting the blade enclosure to

the external network. Four Small Form-Factor Pluggable (SFP) ports provide 1000BASE-SX

interfaces and are shared with four of the copper Gigabit Ethernet links. Two additional copper

Gigabit Ethernet ports are shared with two internal crossover interfaces connecting the pair of

switches (labeled X-Crossovers in Figures 2 and 3). All of these ports can be grouped to support

the IEEE 802.3ad LACP. Each blade server is connected to the backplane using the available

Gigabit Ethernet network interface cards (NICs). The number of NICs on each blade server varies.

Each server, whether it is full- or half-height, supports an additional Ethernet interface providing

Integrated Lights Out (iLO) support.

Software switching features, the Cisco Catalyst Blade

Note: The iLO interface supports a management interface that resides on each server blade. For

more information about the iLO system, refer to the “Management” section of this guide.

Design Guide

Cisco Catalyst Blade Switch 3020 Features

This section highlights information about the protocols and features provided by the Cisco Catalyst

Blade Switch 3020 that help integrate the HP c-Class BladeSystem enclosure into the Cisco Data

Center Network Architecture.

Spanning Tree

The Cisco Catalyst Blade Switch 3020 supports different versions of the Spanning Tree Protocol

and associated features, including the following:

●

Rapid Spanning Tree Protocol (RSTP), based on IEEE 802.1w

●

Multiple Spanning Tree (MST), based on IEEE 802.1s (and includes IEEE 802.1w support)

●

PVST+

●

Rapid PVST+ (RPVST+)

●

Loop Guard

●

UDLD

●

BPDU Guard

●

PortFast

●

UplinkFast (Cisco proprietary enhancement for IEEE 802.1d deployments)

●

BackboneFast (Cisco proprietary enhancement for IEEE 802.1d deployments)

The IEEE 802.1w protocol is the standard for rapid spanning tree convergence, whereas IEEE

802.1s is the standard for multiple spanning-tree instances. Support for these protocols is essential

in a server-farm environment for allowing rapid Layer 2 convergence after a failure occurs in the

primary path. The primary benefits of IEEE 802.1w include the following:

●

The spanning-tree topology converges quickly after a switch or link failure.

●

Convergence is accelerated by a handshake, known as the proposal agreement

mechanism.

Note: The user need not enable PortFast, BackboneFast, or UplinkFast if running RSTP.

In terms of convergence, Spanning Tree Protocol algorithms based on IEEE 802.1w are much

faster than the traditional Spanning Tree Protocol IEEE 802.1d algorithms. The proposal

agreement mechanism allows the Cisco Catalyst Blade Switch 3020 to decide new port roles by

exchanging proposals with its neighbors.

With IEEE 802.1w, as with other versions of the Spanning Tree Protocol, BPDUs are sent by

default every 2 seconds (called the hello time). If three BPDUs are missed, Spanning Tree Protocol

recalculates the topology, a process that takes less than 1 second for IEEE 802.1w.

Because the data center is made of point-to-point links, the only failures are physical failures of the

networking devices or links. The IEEE 802.1w protocol can actively confirm that a port can safely

transition to forwarding without relying on any timer configuration, meaning that the actual

convergence time is less than 1 second.

Design Guide

A scenario wherein BPDUs are lost may be caused by unidirectional links, which can cause Layer

2 loops. To prevent this problem, use Loop Guard and UDLD. Loop Guard prevents a port from

forwarding as a result of missed BPDUs, which might cause a Layer 2 loop that could bring down

the network.

UDLD allows devices to monitor the physical configuration of fiberoptic or copper Ethernet cables

and detect when a unidirectional link exists. When a unidirectional link is detected, UDLD shuts

down the affected port and generates an alert. BPDU Guard prevents a port from being active in a

spanning-tree topology as a result of an attack or a misconfigured device connected to the switch

port. The port that sees unexpected BPDUs is automatically disabled and must then be manually

enabled, giving the network administrator full control over port and switch behavior.

The Cisco Catalyst Blade Switch 3020 supports Per VLAN Spanning Tree (PVST) and a maximum

of 128 spanning- tree instances. RPVST+ is a combination of Cisco PVST Plus (PVST+) and

RSTP, provides the flexibility of one spanning-tree instance per VLAN and the fast convergence

benefits of IEEE 802.1w. MST allows the switch to map several VLANs to one spanning-tree

instance, reducing the total number of spanning-tree topologies the switch processor must manage.

A maximum of 16 MST instances is supported. In addition, MST uses IEEE 802.1w for rapid

convergence. MST and RPVST+ create a more predictable and resilient spanning-tree topology,

while providing downward compatibility for integration with devices that use IEEE 802.1d and

PVST+ protocols.

Figure 4 illustrates an example of Spanning Tree Protocol when using two switches in the

crossover configuration. Each blade switch is dual homed to each aggregation switch through a 2-

port Cisco EtherChannel interface. In this figure the blocked links are indicated in red. In this

example, only four of the eight uplinks from each blade switch are used. The network designer can

make those EtherChannel uplinks more robust (up to four 4 ports each), or use them to connect

other devices such as intrusion detection systems (IDSs) or standalone servers.

Figure 4. Spanning-Tree Example with the HP c-Class Enclosure and Cisco Catalyst Blade Switch 3020s

Design Guide

Note: The IEEE 802.1w protocol is enabled by default when running spanning tree in RPVST+

or MST mode on the Cisco Catalyst Blade Switch 3020. The Cisco Catalyst Blade Switch 3020

enables PVST+ for VLAN 1 by default.

The Spanning Tree Protocol uses the path cost value to determine the shortest distance to the root

bridge. The port path cost value represents the media speed of the link and is configurable on a

per-interface basis, including Cisco EtherChannel interfaces. To allow for more granular Spanning

Tree Protocol calculations, enable the use of a 32-bit value instead of the default 16-bit value. The

longer path cost better reflects changes in the speed of channels and allows the Spanning Tree

Protocol to optimize the network in the presence of loops.

Note: The Cisco Catalyst Blade Switch 3020 supports IEEE 802.1t, which allows for spanning-

tree calculations based on a 32-bit path cost value instead of the default 16 bits. For more

information about the standards supported by the Cisco Catalyst Blade Switch 3020, refer to the

Cisco Catalyst Blade Switch 3020 Overview document: http://www.cisco.com/go/bladeswitch

For more information regarding spanning tree and Layer 2 design in the data center, visit:

http://www.cisco.com/en/US/solutions/ns340/ns517/ns224/ns304/net_design_guidance0900aecd80

0e4d2e.pdf.

Traffic Monitoring

The Cisco Catalyst Blade Switch 3020 supports the following traffic-monitoring features, which are

useful for monitoring blade-enclosure traffic in data center environments:

●

Switched Port Analyzer (SPAN)

●

Remote SPAN (RSPAN)

SPAN mirrors traffic transmitted or received on source ports or source VLANs to another local

switch port. This traffic can be analyzed by connecting a switch or Remote Monitoring (RMON)

probe to the destination port of the mirrored traffic. Only traffic that enters or leaves source ports or

source VLANs can be monitored using SPAN.

RSPAN facilitates remote monitoring of multiple switches across your network. The traffic for each

RSPAN session is carried over a user-specified VLAN that is dedicated to that RSPAN session for

all participating switches. The SPAN traffic from the source ports or source VLANs is copied to the

RSPAN VLAN. This mirrored traffic is then forwarded over trunk ports to any destination session

that is monitoring the RSPAN VLAN.

Figure 5 illustrates the use of RSPAN in a dual-blade switch environment. Here the internal cross-

connects can allow the RSPAN traffic to traverse the backplane from one switch to the other. The

second switch can either send the SPAN traffic out an uplink port to a local IDS device or pass it up

the EtherChannel uplink to the aggregation switch above. Because RSPAN uses its own unique

VLAN, it can use ports that may be blocked by other data VLANs.

Figure 5. RSPAN Example

Design Guide

Link Aggregation Protocols

Cisco Fast EtherChannel interfaces and Gigabit EtherChannel interfaces are logically bundled, and

they provide link redundancy and scalable bandwidth between network devices. PAgP and LACP

help automatically create these channels by exchanging packets between Ethernet interfaces and

negotiating a logical connection. PAgP is a Cisco proprietary protocol that can be run only on Cisco

switches or on switches manufactured by vendors that are licensed to support PAgP. LACP is a

standard protocol that allows Cisco switches to manage Ethernet channels between any switches

that conform to the IEEE 802.3ad protocol. Because the Cisco Catalyst Blade Switch 3020

supports both protocols, you can use either IEEE 802.3ad or PAgP to form port channels between

Cisco switches.

For both of these protocols, a switch learns the identity of partners capable of supporting either

PAgP or LACP and identifies the capabilities of each interface. The switch dynamically groups

similarly configured interfaces into a single, logical link, called a channel or aggregate port. The

interface grouping is based on hardware, administrative, and port parameter attributes. For

example, PAgP groups interface with the same speed, duplex mode, native VLAN, VLAN range,

trunking status, and trunking type. After grouping the links into a port channel, PAgP adds the

group to the spanning tree as a single switch port.

In Figure 6, each blade switch uses an alternative configuration. The switch is no longer dual

homed; instead all the ports are put into a single Cisco EtherChannel uplink to the aggregation

switch above. This single EtherChannel uplink can use up to the full 8 ports, providing a 2-to-1

cable reduction from the servers. In this configuration, the Spanning Tree Protocol may not be

needed because there is no loop in the network if the interconnect ports between the two blade

switches are disabled.

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