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Re: GS752TPv2 and DHCP

Tripo
Tutor

GS752TPv2 and DHCP

Hello all,

 

I hope somebody could help me with my problem. I recently got a GS752TPv2 and I am trying to make it work properly with my DHCP. Here is my installation right now for testing:

 

Internet <-> Router with DHCP <-> GS752TPv2 <-> my compyter

Addresses given by my DHCP are 192.168.1.x

 

If I plug direclty my computer to my router, I get a valid IP address (192.168.1.5 for example) and I can access to Internet. When I plug my GS752TPv2 to my router, it seems the switch doesn't recognize the DHCP and starts with IP 192.168.0.239. Of course, if I plug my computer in the switch, I don't get any IP address because the switch is not a DHCP server and it doesn't access to my router... I tried several configuration on the switch to make it find my router but without success (DCHP mode, static mode, reset, factory reset). I also updated it to last firmware (6.0.4.6) but nothing changed.

 

Did I miss something? 
Thanks in advance,

Regards,

Benjamin

Model: GS752TPv2|48-Port Gigabit Ethernet PoE+ Smart Managed Pro Switch with 4 SFP Ports (380W)
Message 1 of 9

Accepted Solutions
Tripo
Tutor

Re: GS752TPv2 and DHCP

I am replying to myself because Netgear's technical support found the solution. Without really understanding why, it seems my router was creating a loop. I deactivated STP and now everything works perfectly so if somebody also has an issue getting an IP using DHCP, try deactivating STP!

View solution in original post

Message 8 of 9

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schumaku
Guru

Re: GS752TPv2 and DHCP

By default, these switches are L2 devices spanning a transparent LAN. If neither the switch itself nor a connected computer does get a IP address assigned, the first guess is that the network connection from the router to the switch isn't up, or (unlikely as you stated the same issue happens following a switch factory reset) there are multiple VLANs configured for the management, and for the ports used for the link to the router and the computer.

Message 2 of 9
Tripo
Tutor

Re: GS752TPv2 and DHCP

That's exactly my problem, the switch should be transparent and gets an IP from my DHCP but it doesn't, even after the factory reset. I am using nominal configuration (no VLAN, nothing set up) and it doesn't work. I really don't understand. Is there a way for me to run a diagnostic on the switch? I just bought so I don't think the problem comes from the switch itself but (if I'm really unlucky) it might...

Message 3 of 9
schumaku
Guru

Re: GS752TPv2 and DHCP

Link LEDs on both ends of the connection router<-> switch are OK?

 

You can always connect the switch Web UI by temporary re-configuring the computer to the 192.168.0.0/24 subnet (e.g. 192.168.0.123/24 255.255.255.0 subnet, default gateway any other address in that same subnet (and tick the connection config check which does exist on some overly smart OS) on applying the config. Now open the Web UI on http://192.168.0.239/ .... so you can check e.g. the port status on the router connection.

Message 4 of 9
Tripo
Tutor

Re: GS752TPv2 and DHCP

LEDs are ok: green and blinking. It seems the switch is "talking" but it doesn't work.

I attached a screenshot with port configuration of the swith: port 25 on my router and port 32 (not visible on the screenshot) to my computer. As you can see, status is up with speed 1GB (for both of them).

 

Is there a way I can see logs on the switch with IP attribution (connection to DHCP, failing, test...)?

Message 5 of 9
schumaku
Guru

Re: GS752TPv2 and DHCP

Strange.

 

Using the very same LAN port on the router as for the single computer test?

 

Switching -> Address Table ... does this display some more MAC addresses from systems on your network?

 

Lets start with the Monitoring -> Logs -> Buffered Logs (not that I expect much ref. the DHCP)

 

When manually configuring the management interface IP ... can it be reached?

Message 6 of 9
Tripo
Tutor

Re: GS752TPv2 and DHCP

Yes, I am using exactly the same port and the same cable on my router to test the connection to the switch and to double check with my computer.

 

On address table, I can see all the devices plugged to my router (status Learned on the port where my router is plugged-in). My router is listed twice, first with VLAN ID 1 and with VLAN ID 100 which is used for TV. DHCP is on VLAN 1 and all the other devices are listed in VLAN 1. Could that be a problem?

 

On monitoring logs, I don't have "Buffered Logs". I attached memory logs but I don't see anything weird in it.

 

When I manually configure the switch IP address with a valid IP (@192.168.1.251, netmask 255.255.255.0 and gateway 192.168.1.254 -- which is my router address), my router still doesn't see it and to be able to access to the switch, I need to manually setup my computer IP. For short, the IP changed but the switch behave in the same way than with its previous address (192.168.0.239).

Message 7 of 9
Tripo
Tutor

Re: GS752TPv2 and DHCP

I am replying to myself because Netgear's technical support found the solution. Without really understanding why, it seems my router was creating a loop. I deactivated STP and now everything works perfectly so if somebody also has an issue getting an IP using DHCP, try deactivating STP!

Message 8 of 9
schumaku
Guru

Re: GS752TPv2 and DHCP


@Tripo wrote:

I am replying to myself because Netgear's technical support found the solution. Without really understanding why, it seems my router was creating a loop. I deactivated STP ...


There can be other devices connecting e.g. concurrently to the router's WiFi and to an Ethernet port direct or indirect connecting to the switch. The router on it's own (unless there is an incorrect config of a LAG or aggregation between the router and the switch with multiple links) won't create a loop. Just disabling STP instead of finding the effective issue will move the issue to another point...

 

Sonos devices can cause such isues for example.

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