migrate from old layer 3 switch to new layer 3 switch...


What is the best method for moving from one Layer 3 switch to a new Layer 3 switch?

Our old Layer 3 is 10/100 Mbps. We are moving to a new switch that is 10/100/1000 Mbps. Our "network consultants" told me that installing a new Layer 3 is basically " a plug and play" operation. We do not have any special configuration (VLANs for example) in our current switch.

On my first attempt, I plugged just two PCs, our (SonicWall)  firewall, and both domain controllers into the gigabit Layer 3 switch. This is with the idea that if I could get a small configuration working.....then I would add the rest of the devices....and I am done.

I plugged those five devices into the new gigabit Layer 3. I could ping each of those devices among them selves.... But I just could not get to any Internet web page. I believe my problem is that the "default gateway" device was not added to my small configuration. In the past the "default gateway device" was embedded in one of the routers. Essentially all the default gateway (xx.xx.254.253) does is point the system devices (on the main subnet) to the firewall (xx.xx.254.222). If I would have been thinking at the time, I could have just changed the device gateway (on one or both of those two test PCs) to xx.xx.254.222 instead of leaving it at xx.xx.254.253. Anyway, I was running short of my "scheduled downtime"... So after not being able to connect to the Internet, I switched everything back over to original.

Now, I know changing the default gateway to xx.xx.254.222 is a good workaround (for not using the actual default gateway) because I changed one computer to xx.xx.254.222 since I returned to our original configuration. It works fine.

Anyway, I found the router that has the default gateway embedded. I could schedule more downtime and attempt to add the gateway to my same "small configuration of  devices" to see if I can connect to the Internet with the gigabit Layer 3 switch. But I thought it would be prudent to see if there is a better procedure than what I am using to move over to the gigabit Layer 3 switch.

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Default gateway on switch is needed only for traffic that is created by switch itself and directed to different network subnet. If your devices don't get default gateway I guess problem is your DHCP server on network (maybe old L3 switch was DHCP server?).
Why don't you check old L3 switch configuration and make the same configuration on new router (at least similar). And, btw, if there is no any configuration on L3 switch, then, most likely, that switch is used as L2 since routing is disabled by default on most L3 switches. If routing is enabled you should set at least two pieces of information on switch - IP address of some interface and you should set default route (but, on the other hand, if everything is in the same VLAN... I guess you don't need that). :)
If really there was no any configuration on your previous switch, then most likely you don't need any setup on new L3 switch and everything should work when you connect your devices, but if there was some configuration you need to configure new switch.

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Ugo MenaCommented:
Check the configuration on your SonicWALL firewall. Specifically the X0 and X1 interfaces.

X0 is most likely your LAN and X1 is probably your Internet connection or set to use your default Gateway.

If your Sonicwall is handling DHCP, all you need to do is change the default gateway address in your Sonicwall and connect it to the new switch. The rest of the devices will get the new setting via DHCP when connected to the new switch.
LLong29Author Commented:

One point I need to add is that we do not use any DHCP servers. We have only about 300 computers split among 18 of our stores. We simply use fixed addresses for each type of workstation at each store. The only thing that changes per store is the third octet which is the store/router number.

Thank you for your comments. I will start checking each of the points you both mentioned.

L. Long
Ugo MenaCommented:
OK. Got it.
I read your post over again and think you are on the right track.
Since you will continue to use the gateway router you will need to connect it to the new switch when testing connections. That is what is connecting your store into the main network.
As your consultant said, it should be plug and play, just plug all the necessary devices in to test. :)
LLong29Author Commented:
Yes. I found the documentation for installing the (new) CISCO layer 3 switch. And I did have to install two IP addresses for the layer 3 to work. I had to set in its own local IP address and the gateway IP address. Then I simply inter-connected to the two switches and have been migrating the devices from the old layer 3 to the new layer 3. Once all the devices have been moved over...then I simply disconnect the old switch.
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