You can enable DHCP Snooping on the switch along with setting a specific scope on your DHCP servers to hand out address to a certain subnet or range.

DHCP snooping is a security feature that monitors DHCP messages between a DHCP client and DHCP

servers to filter harmful DHCP messages and to build a bindings database of MAC address, IP address,

VLAN ID, and port tuples that are considered authorized. You can enable DHCP snooping globally, perinterface,

and on specific VLANs, and configure ports within the VLAN to be trusted or untrusted.

DHCP servers must be reached through trusted ports.

DHCP snooping enforces the following security rules:

• DHCP packets from a DHCP server (DHCPOFFER, DHCPACK, DHCPNAK,

DHCPRELEASEQUERY) are dropped if received on an untrusted port.

• DHCPRELEASE and DHCPDECLINE messages are dropped if for a MAC address in the snooping

database, but the binding’s interface is other than the interface where the message was received.

• On untrusted interfaces, the switch drops DHCP packets whose source MAC address does not match

the client hardware address. This feature is a configurable option.

Page 448 User guide:

support.dell.com/.../ucg_en.pdf

If all clients on the 2 new switches are getting the IPs from the same second server then you can set up the IP helper command to point the switches to a specific DHCP server address.

IP Helper

The IP Helper feature allows the switch to forward certain configured UDP broadcast packets to a

particular IP address. This allows various applications, such as the DHCP relay agent, to reach servers on

non-local subnets, even if the application was designed to assume a server is always on a local subnet and

uses broadcast packets (with either the limited broadcast address 255.255.255.255, or a network directed

broadcast address) to reach the server.

You can configure relay entries both globally and on specific routing interfaces. Each relay entry maps an

ingress interface and destination UDP port number to a single IPv4 address (the helper address). You can

configure multiple relay entries for the same interface and UDP port, in which case the relay agent relays

matching packets to each server address. Interface configuration takes priority over global configuration.

In other words, if the destination UDP port of a packet matches any entry on the ingress interface, the

packet is handled according to the interface configuration. If the packet does not match any entry on the

ingress interface, the packet is handled according to the global IP helper configuration.

On page 555 of the User guide provided in previous post.

To configure the helper address, identify the router interface that will receive the broadcasts for UDP services. In interface configuration mode, use the "helper-address" command to define the address to which UDP broadcasts for services should be forwarded.

console(config)# interface vlan xx

console(config-if-vlan11)# helper-address xxx.xxx.xxx.xxx

Console(config)#

How this will prevent other clients on the network (not connected directly to 6024/6224) from getting DHCP from 2nd DHCP server and not from the main one?

Thank you

OB

You can use the IP Helper Interface Command described in the User Guide pages 556-558.

 http://support.dell.com/support/edocs/network/PC62xx/en/UCG/ucg_en.pdf

With this command you can specify a DHCP server address to a certain interface (range, vlan).