Network Topology

[SuperDanza]

Hello,

I recently asked a question about connecting MS210s to my existing Cisco 3750 network. Thanks to the support here I was able to successfully add six of those switches to my network.

The next step for me is to figure out what steps to take to replace my 3750 core. The core is running EIGRP but that is a legacy configuration due to some old T1 and T3 links to sites. Everything is now connected via layer 2 point to point fiber. There is no routing on the far end sites. Just 3750 switches running at layer 2. I am thinking that I really can exist in a layer 2 world going forward. Here is what my network is going to look like:

The VLANs exist for management purposes. There are some cases where I need ACLs to prevent a VLAN from accessing another VLAN. That seems pretty straightforward. My questions are:

1. Can I really exist in the layer 2 world with no routing. My network is a true hub/spoke with all far end connections landing on the MS410. Do I need routing? I set this up in a lab and was able to ping from VLAN to VLAN. configure ACLs to limit traffic to certain VLANs and all VLANs were able to access the internet.

2. As asked in the previous post, my plan is to do a shutdown on VLAN 110 on the 3750 stack and then configure that VLAN on the MS410. I am expecting some traffic issues while the new route is learned. I will repeat the steps for the rest of the VLANS. I tested this in a lab with only a few machines and it worked. But lab and real world are two different animals.

3. 192.168.0.1 is currently an old Cisco 2611. This equipment was in service when there were T1 and T3 serial connections. The ONLY work it is doing now is serving as the gateway for VLAN 1. This address is the VLAN 1 address of the MS410. I am thinking I can just disconnect the 2611, connect the MS410 and traffic to 192.168.0.1 will eventually route through the MS410. I can clear the arp cache on the 3750 core to speed things up. THIS WILL NEED TO BE THE FIRST THING I DO WHEN I INTRODUCE THE MS410 TO THE NETWORK. I can move the other connections over time. I still have about 15 more switches to deploy and then I am ready to cutover.

I am looking for any input that would be helpful. As I stated, the last post got my MS210s integrated with the Catalysts (pruning VLANS! Yes! Thank you!). My next step is to remove the 3750 core, replacing it with the MS410.

Thanks in advance!! I am sure I have missed something 🙂

(And I know there is no link to my WatchGuard Access Points - I know I need one, just threw the drawing together quickly. They will connect to MS210s trunked with a native VLAN of 110 and allowed 110 and 85)

[PhilipDAth · Accepted solution]

I don't think you need any dynamic routing protocols.

With 6 sites - I think I would do a big bang cut over.  Change the whole lot over at once.

[SuperDanza]

Thank you for verifying the routing question.

Doing a rip and replace was my original plan. However this work involved a police department and downtime needs to be kept at a minimum. I also had a flashback of being 8 years old and taking my sound effects machine apart and then sitting on the floor looking at all of the pieces forgetting how it all went together.

On paper this is a very simple network. My plan is to replace the edge switches, including the five at the PD, and then do a rip/replace of the Core stack on a Friday night. 

I appreciate the time you took to read and comment on my post. I feel better moving forward with this plan. Thank you.

[PhilipDAth]

Ask them when their lowest activity period is.  Monday 9am, Tuesday 2am, Wednesday 3pm, etc.  Book the change in then.

[SuperDanza]

That's a fine thought. I can work anytime after midnight. We are a small community and it's pretty quiet at night. I can keep a 3750 trunked back to the core that keeps key connections up while I rip out the rest of the switches. Downtime would be minimal. It's the core that concerns me. Thinking about it I can replace three of the distribution switches in that stack ahead of time and just have to deal with replacing the remaining layer 3 switch with the layer 2 MS410. 

I am probably making this more complicated in my head than it is. But measure 15 times, cut once...