Core switch replacement 3550 => 3750

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May 24th, 2014
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Hello everyone!

I'm having some concerns regarding to our core switch replacements.

We have 2 3550s core switch and 6 2960s/2950s and a couple of dozens servers, NAS drives, etc...

The core switches will be replaced with 3750 with ip image license on them.

The trouble is we have more than 20 VLANs with more than 10 HSRP virtual IPs.

I've tried to hook up the new switch with disabled VLAN and HSRP (only layer 2 access) and obviously the servers on the distribution switches strated to loosing the ISP access, because the VLAN and therefore the HSRP vips were disabled on the new switch.

I was thinking to kill the second switch which only has the standby vip HSRP IPs and enable all the VLANs with the HSRP on the new switch.

What would be the safest method to switch over to new HSRP core switch?
(Both 3550 need to be replaced)

The main issue is the live traffic, I can't disable and enable 1 by 1 the HSRPs on the old/new switches because it takes ages.

Our system has dozens of live traffic which can't be interrupted in any way.
I can't put every details onto the picture that I quickly draw, because we have about 100 servers/switches/routers/nas etc...

Also from the picture is missing the routers and the firewall vlans. (all vlans)
Every parts of the network cross connected for redundancy and obviously the picture does not contain that part at all.

I would much appreciate every idea/help how to do it as safe as possible.
Could not find much info regarding to core switch replacement, usually this part of the network has not been bothered much, so therefore less experience/info about this. ;)

There is a picture about the network: http://www.7layer.org/downloads/netw1.png

Thanks very much in advance for every help!

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Leo Laohoo Sat, 05/24/2014 - 07:48
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I am apprehensive about your "topology".  Looks very familiar.  

7layerorg Sat, 05/24/2014 - 11:52
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Hi Leo,

Well this is an inherited network, so regarding to the design I just got it like this. (does not mean it's good although)

However which part makes you worried?

Although I can't really make big changes on it, because it just works fine.

Any thoughts on the core switch replacement?

 

 

Leo Laohoo Sat, 05/24/2014 - 17:07
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What is the distance between the core switches? 

Why the choice of 3750?

What switch are you planning to link or connect your "hundreds" of servers to?

7layerorg Sun, 05/25/2014 - 09:22
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The core switches in the same rack, the access layer switches all of them less than 10M.

Well 3750 knows much more than we need at this layer.

And the access layer switches are 2960s and 2 old 2950s.

Leo Laohoo Sun, 05/25/2014 - 21:29
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Let me get this straight ... Your core switches are 3750 switches?  They are in the same rack?   And you are running HSRP?

kaaftab Wed, 05/28/2014 - 03:08
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well its a live environment no one will suggest you to replace it in one go .I belive every one will recommned you to shift one network at a time if you donot have any DR plan with you.Although you can replace it in on go with downtime but its highly not recommended .

Leo Laohoo Wed, 05/28/2014 - 05:09
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Can I also ask if you can post the complete and un-edited output  to the command "sh version" of your 3750 core switches?

Sajid Ali Sun, 05/25/2014 - 22:15
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The safest way, you suggested by your self :)

<span style="font-family:courier new,courier,monospace;"><span style="font-size: 14px;">&quot;&nbsp;was thinking to kill the second switch which only has the standby vip HSRP IPs and enable all the VLANs with the HSRP on the new switch.&quot;</span></span>I think you have to comprise to other issue and you should shift 1 by 1 virtual IP to new switch.

 

Sajid Ali Pathan

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