Switch is working, but not showing up on LAN scan?

Ive got a netgear smart switch that still seems to be working as all of the devices connected to it are still showing up on a LAN scan and are still functioning on the network. What's odd is that the switch itself is no longer showing up on a LAN scan. Any idea why that would be ?

My config is : router (draytek 2860) --> netgear 5 port smart switch (GS105Ev2) --> netgear 5 port smart switch (GS105Ev2) --> netgear 16 port smart switch (GS716T)

Cabling is a mixture of cat5e and cat6, the smaller 5 port switches act as terminals in different locations as there is no direct run between the router and the rack which houses the 16 port switch.

What's odd is also that only 1 of the 2 5 port switches that sit between the router and the 16 port switch is showing up in the LAN scan.

sam

Posted 2017-12-26T19:36:02.220

Reputation: 3 411

have you tried turning the switch off and on? Sometimes that helps. – LPChip – 2017-12-26T20:11:30.190

@LPChip on of the first things i tried, ive also tried factory resetting the switch but to no avail – sam – 2017-12-26T20:47:43.587

Hoe are you doing the “lan-scan” and to which switch is the computer doing the scan attached? – Tonny – 2017-12-26T21:08:29.457

@Tonny im doing the LAN scan using this tool : https://www.iwaxx.com/lanscan/ - scanning the range 192.168.1.1 to 192.168.10.254 . Im running the scan on my laptop which is connected over wifi to either 1 of 2 wireless access points, 1 of the access points is connected to the 16 port switch in question, the other is connected to the router.

– sam – 2017-12-26T21:12:30.320

@sam I know that tool. And there is no way you can get it to scan 192.168.1.1 to 192.168.10.254 because that ip-range is not a single range. LanScan wil only scan the ip-range your computer is connected to, and nothing else. Those ip-ranges make no sense at all. – Tonny – 2017-12-26T22:05:10.410

@Tonny i thought you could change the range in the top bar. See this image : https://imgur.com/a/J4bkj - For instance the site im having trouble with has a range of 192.168.1.x and a Lan to Lan VPN with another site with a range of 192.168.10.x if i set the range 192.168.1.1 to 192.168.10.254 as per this screenshot it shows me the devices at both sites.

– sam – 2017-12-26T22:23:32.700

I believe there is a management suite for the switch - can it connect to both switches and what info it gives (especially regarding IP address)? Try to scan also using nmap and show the results.

– harrymc – 2018-01-15T10:53:49.053

Answers

From the NETGEAR webpage:

Note: Make sure that the computer you are using is connected to the switch with an Ethernet cable. The computer that you are using must have an IP address on the same network as the switch's IP address.

You stated that you are connected via Wi-Fi. Let's remove all the variables.

Unplug the switch from your other network devices. (This will stop the default DHCP behavior)
Plug your computer directly in to the switch using an ethernet cable
Manually set your IP address to an open address in the default range "192.168.0.XXX". (Like 192.168.0.210)
Use the "ProSAFE Plus Configuration Utility" to find the switch.

If you still can't see it:

Factory reset the switch
Goto http://192.168.0.239

HackSlash

Posted 2017-12-26T19:36:02.220

Reputation: 3 174

1Thanks @HackSlash this worked, i had to run steps 1-3 and then i ran a lan scan and the switched showed up on 192.168.0.239 and i could access it through a browser (ProSAFE Plus Configuration Utility not required). Whats really weird is that if i didnt set my computers IP to the 192.168.0.XXX range even if i scanned the 192.168.0.XXX range from 192.168.1.XXX the switch still wouldnt show up. Once i gained access to the switch i set it to have a static IP on the 192.168.1.XXX range. – sam – 2018-02-11T14:54:16.690

1@sam Not being able to scan the switch from a computer in another ip-network (even when both ARE connected to the same ethernet) is completely normal. It is supposed to work that way. To get from one ip (layer3) network to another a router must be involved. Even if both ip-ranges live on the physical layer 2 (ethernet) network. – Tonny – 2018-02-11T15:59:27.103

@Tonny is right. This gets in to subnetting. It is possible to open up your subnet mask to 255.0.0.0 if you want to scan a larger subnet. This might take a very long time to scan. – HackSlash – 2018-02-12T16:14:13.290

Without further details on your network setup I can only list a couple of possibilities here:

Your doing an IP-address scan, but the switch doesn't have an IP-address set.
Switch management IP-address is in another IP-range so it doesn't react when you are scanning your range.
Switch management VLAN is another one than the VLAN on which you are doing the scanning.
Switch management interface is "hung up" and isn't responding. (Switch reboot should clear that, but obviously that will cause a short outage for the other devices.)
As the previous item, but it isn't really "hanging" but just to busy to respond because it tries to deal with other, more important, traffic first. (I've seen that happen with networks suffering lot's of broadcast traffic and also on networks where some devices produced a lot of jumbo-frames.)

There are probably several other causes that can produce the effect, but those are the most common ones I know about.

Tonny

Posted 2017-12-26T19:36:02.220

Reputation: 19 919

Thanks @tonny , ive updated my question to provide me info on my setup, ive tried power cycling the 16 port switch (by using the reset button and by pulling the plug) but to no avail. Ive also tried factory resetting the switch using the factory reset button but again to no avail. Whats also odd is also that only 1 of the 2 5 port switches that sit between the router and the 16 port switch is showing up in the LAN scan. – sam – 2017-12-26T20:46:04.740

It's quite possible that the factory default is a static IP address that your network would need to match. You'll have to check the manual for the address. – Zac67 – 2017-12-26T20:51:25.090

@zac67 - Possibly, ive followed this guide also and tried to access the default static IP as well as using their discovery tools but to no avail : https://kb.netgear.com/30418/What-is-the-default-IP-address-of-my-NETGEAR-Web-Managed-or-Smart-Managed-Switch

– sam – 2017-12-26T21:37:42.340

Have you tried a switch separated from the rest? If they all default to the same address and sense an ARP collision they might deactivate IP altogether. – Zac67 – 2017-12-26T22:44:59.343

Switches do not need an IP address to operate as a switch - the purpose of giving a switch an IP address is for management access to the switch - so the switch will work as a switch even if it has bad or unreachable IP addresses

For both the GS105Ev2 and the GS716T the switch will either get a DHCP address or if it cannot then get the address 192.168.0.239/24.

You state you are scanning 192.168.1.1 to 192.168.10.255. First what is your DHCP server giving out? Second this does not include 192.168.0.239 which is the default for both switches so change that. Finally what address do you get for the GS105Ev2 switch that you see - if its 192.168.0.239 then I believe all three have not got DHCP server assigned address and so have the same IP address and so only one will show up. If this is so then they probably are "fighting" over the address - in that they will all respond to ARP requests and whichever is last will win, This makes it very difficult to connect to them.

If its not 192.168.0.239 then check your DHCP server configuration page on the draytek 2860 and see that the address is being issued and to which MAC - hopefully it matches that on a label on the outside of switch - the last octet may be different from what you see on the network as each VLAN needs a different MAC address. Then you can tell which switch is getting an address

If its the closest then maybe DHCP is being stopped by the first switch - so if you can manage the switch using the address you see then check the configuration of the switch and fix it. If its the second switch you can reach ... well , I don't know, check the above and update the question.

Ross

Posted 2017-12-26T19:36:02.220

Reputation: 1 096

The router (acting as DCHP server) is set to give the switches MAC address reserved IP. The gateway is 192.168.1.1. 2) Ive expanded the LAN search range to include 192.168.0.x but nothing unfortunately.

< – sam – 2018-01-16T15:54:10.947

OK , without seeing all the configuration I think the best thing to try is hackslash answer. – Ross – 2018-01-17T00:50:31.690