3750 stack to 6509 VSS migration

Unanswered Question
Aug 15th, 2008

Looking into migrating our 3750 stack to 6509 VSS and would welcome all suggestions.

The current 3750 core stack is the default gateway on the network, as well as interface vlans, port-channels, and ip routes, and ACL's.

I see a couple of options:

1. Configure 6509 and then just move the 3750 connections over to 6509 with some short downtime.

2. Implement HSRP between 6509 and 3750, change the default gateway as the HSRP address then gradually move connections from 3750 to 6509.

3. Any suggestions.

Some questions:

Interface Vlan configs - would there be potential issues with Vlans during migration?

Also, would you recommend installing a single 6509, migrating, then configuring the VSS? Or configure the 6509 for VSS, then perform the migration?


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Marwan ALshawi Fri, 08/15/2008 - 08:16

i think option 2 not possiable

because with VSS

u gonna be able to configure one device and the secondary will take the config fron the primary

and during the conifg u will need to restart and hsrp will not be apilcable

so i think better to use the option 1

good luck

if helpful rate

Joseph W. Doherty Fri, 08/15/2008 - 08:56

Without a better understanding of your logical and physical topologies, hard to suggest either.

Before replacing the 3750 stack, I would lean toward VSS being functional, reguardless of method of cutover.

Using the slow migration method, HSRP gateway transfers, is a nice method to migrate from one device to another, but your real issue is you have a single logical core and you would need to first migrate it to a dual core. For instance, since you're using a 3750 stack, is the gateway address even HSRP? If not, there can be network interruption as the gateway MAC changes.

In other words, how difficult would it be to bring a dual core on-line for slow cutover vs. just doing a one-time cut over from single core to another single core?

Tim Johnson Fri, 08/15/2008 - 09:50

Thanks for the info - here is a basic idea of the Topo (Hope ti comes out)

To Edge Devices


| To DMZ

| |

| |

| |

Port-CH. ___________ Port Ch. to Closets

3750 Stack ---------------|Core Stack |------------------

24x7 servers---------------|___________|------------------




Port-CH. ||

3750 Stack ------------------ |

8x5 servers -------------------

The core is really the core, hub and spoke, everything comes to this and it houses the VLAN interfaces and some routing for our two separate FW's and ISP's.

This is a mid sized network, about 20 port channels to other closets, about 20 Vlans, nothing real major.

I'd like to transition with no-to-little downtime, however, for simplicity, I am debating about just configuring the 6509 VSS, then schedule some downtime for an hour and bring up piece by piece.

Thanks again.


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