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I have a small office network, around 10-15 devices. The router at present started causing problems and considering it's a 8-years-old SMC I bought a new one for replacement.

What I am worried about is what is going to happen when I plug the new one? It is a different brand, so I presume the configuration file backup from the SMC will not be useful. I am not a network engineer and it will be tricky for me to reconfigure the whole network from scratch.

So, is the network going to crash? What can I take note of before replacing the routers? Is there a way to exchange the settings from the old to the new one(a general way, I do realize this could be really brand specific)?

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    If its a moderately complex network with customization's in the router, you should hire it done by a competent network engineer.
    – Moab
    Dec 29, 2015 at 12:44
  • I am not entirely sure how dependent on the router the network is.. When I go to the router's menu I am pretty much confused what to look for, as it is times more complicated than a normal router's settings page.
    – Phantomazi
    Dec 29, 2015 at 12:47
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    Manually go through every detail of the configuration of the existing router and make sure you understand it all. Do research or ask questions if necessary. Then look at the configuration scheme for the new router and make sure you understand how to make it do everything the existing router does. Dec 29, 2015 at 12:47
  • @Phantomazi that is another reason to have a professional do the job, if you screw it up it just makes it that much harder for the person you should have hired in the first place.
    – Moab
    Dec 29, 2015 at 12:56

2 Answers 2

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There really isn't enough details to fully solve your problem. Is the switch currently managed? What's the current configuration like? Are you using wireless? Is the new switch managed?

Assuming both are managed, just using the old configuration may not work as the syntax to certain functions may have changed. Best bet, match your configurations and install outside of business hours so you can trouble shoot any issues after it has been installed.

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Some things you may have to configure:

  1. WAN address, i.e., the "outside" address for the router - for a small office it is probably dynamically assigned by DHCPand, if so, the new router may pick up the address it needs. But that's not guaranteed even for a small office/home office (SOHO) configuration. It could be a static IP address. If so you would need to know the currently assigned WAN IP address, subnet mask, and gateway address for the WAN side of the router. So you need to determine whether the current router is using static addressing or DHCP for the external WAN interface.

  2. LAN address - the LAN side of the router will likely be using a private network configuration. But even if it is using private IP addresses for the LAN side, you can't count on the new router using the same private IP address block as the old one, especially if the routers are from different manufacturers. The 192.168.0.0/16 block is the most typically used block for routers designed for SOHO use. But, even if both routers are using that class C block of addresses, your new router may not be using the same subnet for the LAN side of the router as the old one. E.g., the old one might use 192.168.0.0/24 while the new one might use 192.168.1.0/24. That means the systems connected to your router would now have IP addresses in the range 192.168.0.1 to 192.168.0.254 whereas they would all have to be readdressed to addresses in the range 192.168.1.1 to 192.168.1.254, if they currently have static IP addresses rather than ones dynamically assigned by DHCP from the current router or you need to change the LAN addressing on the router, which is usually the easier course of action. If every system on the LAN uses dynamically assigned addresses they get from the router, you don't have to worry about the LAN addressing, but bear in mind that even if they are using DHCP to get their addresses, they might not be getting those addresses from the router. E.g., there could be another DHCP server on the network from which they get their addresses, such as a Windows Active Directory domain controller, so you would then still need to make sure the new router is consistent with the old one.

  3. Port forwarding - do you have any servers on the LAN that are accessible from the Internet? E.g., a web or FTP server. Or do users remotely connect to their office systems sometimes using RDP, SSH, etc.? If so, you will likely need to set up appropriate port forwarding, since the current router is likely using Network Address Translation to make the internal system(s) accessible from the Internet. So you would need to look for port forwarding or firewall settings in the old router and configure the new one to match. The procedure for configuring such settings is likely to be different for routers from different manufacturers or even between different models from the same manufacturer.

  4. Firewall rules - often for SOHO configurations all traffic is allowed outbound, but even for SOHO configurations, a network device facing the Internet may be configured to disallow certain traffic. E.g., peer-to-peer (P2P) traffic or access to certain websites deemed inappropriate. If the old router performs that function, you may need to configure the new one to act similarly.

  5. Wireless LAN - the LAN side of the router may be providing both wired and wireless access. For wireless access, you either have to reconfigure the systems on the LAN to use the SSID and passphrase/key of the default settings for the new router or reconfigure the SSID and a passphrase for the new router to match those of the current router. The latter may be the easiest course of action, if most of the 10 to 15 systems are using wireless connectivity. Though, if the current router is providing wireless access and is 8-years old, it might be using an older wireless standard such as WEP or WPA, which are no longer considered secure, so you should switch systems to a newer standard such as WPA2, so you might need to reconfigure systems on the LAN in such a case. Though WPA2 superceded WPA in 2004, so, hopefully, you won't have to worry about that.

It is highly unlikely you can export the settings from the current router and import a file produced by the current router into the new one. Even if both routers were from the same manufacturer, but different models, that might not work. And the exact steps to configure such settings in routers will differ from manufacturer to manufacturer and even between different models from the same manufacturer.

You could examine the settings of the current router and try to make the new router's settings match then remove the old one and put in the new one at a time when there is going to be less impact to users, e.g. on a weekend, if no one usually works at the office on a weekend. Then test each system on the LAN to make sure it has Internet access and verify, if there are any systems that should be accessible from outside the network, that port forwarding is working, if it is needed. If there are problems you could just pull out the new router and put the old one back in place until you can figure out how to resolve the problems.

It is also possible that the network configuration at the office is uncomplicated, i.e., no systems need to be accessible from the Internet and that both the WAN and LAN sides use DHCP with the router functioning as the DHCP server for the LAN side, so that you could just replace the new router with the old one and everything would work as it does today with at most, perhaps, only a change on the wireless side for an SSID and passphrase/key and, perhaps, a reboot of systems so they pick up any needed IP address change on the LAN side or, alternatively, issuing an "ipconfig /renew" command at a command prompt on Windows systems to have them query the router for new DHCP-assigned settings.

If you want to become familiar with networking and how to configure routers and can test the new router's configuration at a time that won't have a significant impact to users, this would be an opportunity to do so. The easiest course and quickest path will likely be to hire someone with network experience to do the work, as others have suggested, if you don't have the time or inclination to, perhaps, work through some initial problems if you make a mistake or overlook some setting that needs to be in the new router.

If the office doesn't currently have someone that provides IT support, you can likely find someone in your area who provides support to small businesses who can do the work for you. If you don't know of anyone currently, you could ask other small business owners in the area for a recommendation of someone.

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