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Juniper Networks/Cisco Systems Switch Interoperability Cookbook

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Objective!

To verify interoperability of Juniper VLAN spanning tree protocol (VSTP) and Cisco

per-VLAN spanning tree protocol plus (PVST+) between Juniper and Cisco switches,

respectively.

To measure convergence time of a VSTP-PVST+ topology between Juniper and Cisco

switches after link failure.

Background!

With Juniper’s VLAN Spanning Tree Protocol (VSTP), Juniper switches can run one or

more spanning tree instances per VLAN. As stated in the Junos Software Guide, VSTP

“enables more intelligent tree spanning, because each VLAN can have interfaces enabled

or disabled depending on the paths available to that specific VLAN.”

The goal of this exercise is to demonstrate interoperability in a multiple-VLAN

environment using VSTP running on Juniper EX switches and PVST+ running on Cisco

Nexus or Catalyst switches.

Topology!

This example uses redundant links between two Juniper switches and one Cisco switch.

VLAN IDs of 2001 and 2002 have been defined on both the Juniper and Cisco switches.

VSTP is enabled on the Juniper switches, while the Cisco Nexus 7010 runs Rapid

PVST+.

Figure 15 illustrates the VSTP-PVST+ validation test bed. This example involves a

standalone Juniper EX4300 switch; a Juniper Virtual Chassis Fabric (comprised of two

Juniper QFX5100 and one Juniper EX4300 switches); and a Cisco Nexus 7010.

As shown in the figure, the links interconnecting each switch are trunk ports that allow

tagged traffic from VLAN IDs 2001 and 2002. Two access-mode ports are configured on

each switch: One apiece for VLAN IDs 2001 and 2002. Traffic offered from the Spirent

TestCenter traffic generator/analyzer verifies the spanning tree topology in each VLAN.

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Cisco Ex SERIES Instrukcja Użytkownika Strona 65