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New Member

Network Card DHCP Server


How the DHCP Server works in an environment of several VLAN?

Like him it does communicate?

The NIC's different?

How can I know if my NIC multiple VLAN support?


Re: Network Card DHCP Server

Normally, your DHCP server has several DHCP scopes and each scpe is assigned to a dedicated Vlan.

On your L3 switch or router, you need to configure 'ip helper-address ' on each Vlan interface so that all DHCP clients can grab an IP from this server.

All NIC are the same, except some support 10/100Mbps or 10/100/1000Mbps speed (UTP-copper), some 1000Mbps only (fiber).

NIC does not come by supporting single or multiple Vlan. That is handled by L3 switch/router to do and ensure inter-vlan routing works fine.



New Member

Re: Network Card DHCP Server


I don't have router in my LAN. Only some switch and 3 vlans.

The port of switch L3 must be configured like trunk, all right? But as the request it returns for the sender if the frame isn't tagged? Who tag the frame isn't server nic?

Re: Network Card DHCP Server

Before that, I need to understand your network setup.

So, you only have a L3 switch, and configured with 3 Vlans. Meaning this switch is doing inter-vlan routing as well, right?

Correct me if I am wrong, I believed your L3 switch has 3 interface Vlans, i.e Vlan10, Vlan20 & Vlan30, and each Vlan carry certain block of IP Address, example -, & And maybe you used 10.1.x.1 as interface IP for each Vlan.

In this case, routing or communication between Vlans is handled by the L3 switch (enabled using ip routing command). If your server sits in Vlan10, and need to talk host in Vlan30, the L3 switch will do the routing from Vlan10 to Vlan30. Put it this way, your server will first talk to ist gateway of, and from here, the switch (via Vlan10) will check the destination IP (and port), and when it sees the Vlan30, it will forward it there,, but of course, it will also check other things like arp table / mac address of the target host.

This is more or less how things work in a switched (with L3) network environment.

The above is a straight forward setup with only one (1) L3 switch and 3 Vlans. But if you need to use turnk, it means you have another switch connected to the main switch via trunk port (encap either dot1q or ISL). The trunk is needed to allow all available Vlans to pass through the link because the other switch hosts users belongs to the 3 Vlans.