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Title: I created a new vlan and added to the trunk port, but it doesn't have an internet connection. [Print this page]

Author: infotech@trusty Time: 2026-1-6 14:10
Title: I created a new vlan and added to the trunk port, but it doesn't have an internet connection.
I created a new VLAN, which is 40; the IP address would be 10.40.0.1. When I connect a device to that VLAN, it doesn't have a internet connection.

What I tried:
Device 1 is connected to that new VLAN 40, which doesn't have internet and can't ping other VLANs within the L3 switch.
Device 2 is connected to another VLAN: it can access the internet and can ping Device 1 and the SVI of VLAN 40.

What is the cause of this?

Author: v-yimengling@ru Time: 2026-1-6 14:36
Hello sir, what is the model of your device? Is it configured with a DHCP address pool? And is the device configured to allow this VLAN on the downlink interface?

Author: infotech@trusty Time: 2026-1-6 14:40

GATC-Emily replied at 2026-1-6 14:36
Hello sir, what is the model of your device? Is it configured with a DHCP address pool? And is the d ...

L3 Switch Model: CS83-24GT4XS-P

Yes, my device can get an IP from that VLAN, and it is pointed to the port interface.

Author: v-yimengling@ru Time: 2026-1-7 09:58

Trusty Hoister replied at 2026-1-6 14:40
L3 Switch Model: CS83-24GT4XS-P

Hello sir,

What is your network topology? After connecting to VLAN 40 and obtaining an IP address, can you successfully ping the gateway IP address and the upstream device's IP address?
Also, are you enabling DHCP snooping on any ports? If so, please disable it and test again.

Author: infotech@trusty Time: 2026-1-7 16:44

GATC-Emily replied at 2026-1-7 09:58
Hello sir,

What is your network topology? After connecting to VLAN 40 and obtaining an IP address ...

This is my topology.
The VLANs are configured in the L3 switch.

And DHCP snooping was enabled and disabled already but didn't work.

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