3 - Virtual_Chassis

Copyright © 2005 Juniper Networks, Inc. Proprietary and Confidential www.juniper.net

4-1

Virtual Chassis

© 2008 Juniper Networks, Inc. All rights reserved. 2

What Is a Virtual Chassis System?

A collection of interconnected EX 4200 switches that are represented and managed as a single entity•Consists of 1 to 10 EX 4200 switches•Provides a scaling solution within a switching

environment• Allows up to 480 10/100/1000 Ethernet ports


Benefits of a Virtual Chassis System

Managed as a single switch•Simplifies management tasks such as software

upgrades•Spanning Tree Protocol is not required within Virtual

Chassis systems Provides control plane redundancy

•Facilitates master and backup Routing Engine election and management

Allows growth and expansion based on needs•Start with a single EX 4200 switch and grow as

needed (up to a maximum of 10 EX 4200 switches)


Virtual Chassis Components (1 of 2)

EX 4200 platform switches•1 to 10 EX 4200 switches can be interconnected•Varying EX 4200 platforms supported in Virtual

Chassis systems PFE

•Each EX 4200 switch has 2 or 3 PFEs• 24-port platforms have 2 PFEs• 48-port platforms have 3 PFEs

•The PFEs interconnect to form the backplane


Virtual Chassis Components (2 of 2)

VCPs:•Use proprietary VCB cables •VCPs are located on the rear of EX 4200 switches•Each EX 4200 switch comes with a .5 meter VCB

cable• Longer VCB cables are available

•No configuration required• Ports can be enabled or disabled

VCEPs:•Use fiber optics to connect remote member

switches•Require 2x10 Gigabit Ethernet uplink module•Must be enabled


Deployment Options

Some common deployment options include:•Single-rack application

• Generally spans less than 5 meters•Top-of-rack application

• Can span up to 15 meters•Remote wiring closet application

• Uses VCEPs to interconnect switches in remote wiring closets; can span more than 500 meters


Deployment Scenarios (1 of 3)

Single-rack application:



Top-of-rack application:



Remote wiring closet application:

Distribution

Closet - East Closet - West

10-Gigabit VCEP10-Gigabit Uplink

VCP


Installing a Virtual Chassis System (1 of 2)

Recommended process:1. Install desired master switch

• Power up desired master switch— switch becomes master and obtains member-id 0

• Assign mastership priority (255)

2. Add desired backup switch • Connect to master using VCB

cable• Power up desired backup switch—

switch is elected as backup and assigned member-id 1

• Assign mastership priority (254)

0

1

2

3

4

Linecard

Backup (Backup RE)

Master (Active RE)

Linecard

Linecard

ON

ON


Installing a Virtual Chassis System (2 of 2)

Recommended process (contd.):

3. Add line card switch• Connect to switch above with

VCB cable• Power up third switch—switch

becomes line card and is assigned member-id 2

• Assign desired mastership priority

4. Repeat Step 3 to add subsequent line card switches• Last line card switch completes

loop by connecting with master

0

1

2

3

4

Linecard

Backup (Backup RE)

Master (Active RE)

Linecard

Linecard

ON

ON

ON

ON

ON


Connectivity

Single management interface• Individual management Ethernet ports on member

switches are tied to a special management VLAN associated with a Layer 3 virtual management interface (vme)

Single management IP address•The Virtual Chassis system is managed as a single

network element; therefore, it has only one management IP address

Single virtual console•Connection to a console on any member switch in a

Virtual Chassis system is redirected to the VC master by virtual console software running on all member switches


Software

Software upgrades need be performed only on the master switch

Software image compatibility check:•Member switches must be running the same software

version as the master to be part of a Virtual Chassis system

• If a version mismatch exists, a syslog message is generated•The master switch performs software compatibility

checks on the JUNOS software version on each member switch

• Switches with different hardware versions or model numbers can be members of the same Virtual Chassis system

•A CLI command is available to upgrade incompatible switches by downloading the correct image from the master over the Virtual Chassis cable


Roles and Responsibilities

Master switch:•Manages all switches participating in the Virtual Chassis

system•Runs JUNOS software in a master role•Runs chassis management processes and control protocols

Backup switch:•Maintains a state of readiness should the master fail•Receives synchronized protocol state and forwarding table

information from master switch•Runs JUNOS software in a backup role

Line card:•The remaining member switches in the Virtual Chassis

system are candidate switches operating as if they are line cards


Mastership Election

Mastership determination:1. Member with the highest user-configured priority

• Priority range is 1–255, factory-default value is 128

2. Member previously functioning as master prior to reboot

3. Member with the longest standing uptime• Difference must be greater than 1 minute

4. Member with the lowest MAC address• Used as tie breaker if all is equal through the first 3

determination points

Configuring mastership priority:[edit virtual-chassis]user@switch# show member 0 { mastership-priority 255;}member 1 { mastership-priority 254;}


Mastership Election Considerations

Once the master is elected:•The member that is second in the master election

process becomes the backup switch•If a master or backup fails, one of the line card

switches is elected as the new backup switch•Preemption occurs when a switch with a higher

mastership priority joins the Virtual Chassis system


Member ID Assignment

Member ID assignment and considerations:•Master switch typically assumes member ID 0•Master switch assigns unique member IDs (1–9) to

each member switch •Member IDs are assigned in ascending order

based on the sequence in which member switches were added to the Virtual Chassis system

•Member ID is preserved across reboot within a Virtual Chassis system

•Member ID serves as slot number for interface naming

•Member ID can be manually configured through the CLI


Topology Discovery (1 of 3)

VCCP is used to exchange LSA-based discovery messages•Discovery messages are exchanged between all

PFEs and build member switch topology and PFE topology maps

Each switch runs shortest-path algorithm for each PFE•Creates PFE map tables that outline shortest paths

between all PFEs Source ID egress filter tables prevent

broadcast and multicast packets from looping•Filter tables are built for each PFE



b ca e fd h ig

Physical Virtual Chassis Cabling

Virtual Chassis Backplane Cables

a

i

b

h

d

f

e

c

g

Logical Virtual Chassis Ring Topology

Virtual Chassis Backplane

Note: a, b, c, … i are PFEs

Example of topology discovery with the SPF algorithm:



Example of topology discovery with the SPF algorithm (contd.):

a

i

b

h

d

f

e

c

g

Logical Virtual Chassis Ring Topology

Virtual Chassis Backplane

Note: a, b, c, … i are PFEs

a

b

i

c

h

d

g

e

f

PFE a’s Rooted Reachability SPF Tree

g

f

h

e

i

d

a

c

b

PFE g’s Rooted Reachability SPF Tree


0

1

2

3

4

ge-0/0/10

ge-3/0/14

ge-0/0/28

ge-2/0/47

Packet Flow Overview (Interchassis)

Packet flow example:•Packets always take the shortest

path• Shortest path is determined by

hop count and bandwidth•Packets going from ge-0/0/10 to

ge-3/0/14 pass through member 4 to reach member 3 because 0 to 4 to 3 is only one hop, whereas 0 to 1 to 2 to 3 is two hops

•Packets going from ge-0/0/28 to ge-2/0/47 pass through member 1 to reach member 2 because 0 to 1 to 2 is only one hop, whereas 0 to 4 to 3 to 2 is two hops


Operational Monitoring

Key operational commands:•Use show chassis hardware to view installed

hardware and inventory details for Virtual Chassis system

•Use show virtual-chassis status to verify status and role of individual members within the Virtual Chassis system

•Use show virtual-chassis active-topology to view active topology details within Virtual Chassis system

•Use show virtual-chassis vc-port to view VCP status and associated details

•Use show virtual-chassis member-config to view Virtual Chassis configuration for individual members

•Use show virtual-chassis protocol commands to view interchassis communication details and status

Documents

3 - Virtual_Chassis