DHCP Client
The request is a subnet-directed broadcast and is addressed to UDP port 67. A limited IP broadcast is addressed to IP address 255.255.255.255 and is not forwarded by the RUCKUS Layer 3 switch or other IP routers. When the BOOTP or DHCP client and server are on the same network, the server receives the broadcast request and replies to the client. However, when the client and server are on different networks, the server does not receive the client request because the Layer 3 switch does not forward the request.
You can configure the Layer 3 switch to forward BOOTP or DHCP requests. To do so, configure a helper address on the interface that receives the client requests, and specify the BOOTP or DHCP server IP address as the address you are helping the BOOTP or DHCP requests to reach. Refer to configure a helper address. Instead of the server IP address, you can specify the subnet directed broadcast address of the IP subnet the server is in.
The DHCP client supports the dynamic IP address allocation method, where an IP address is assigned to a client for a limited period of time (or until the client explicitly relinquishes the address). Permanent IP address allocation to the hosts and statically assigned IP addresses are not supported.
RUCKUS devices support a DHCP client on physical ports, LAG ports, and Virtual Ethernet ports. The DHCP client is not supported on tunnel ports or stacking ports when stacking is enabled.
The DHCP client is enabled by default at bootup on all RUCKUS devices.
DHCP Client Behavior on a Layer 3 Device
On a layer 3 device, all physical ports act as
DHCP clients by default. When a DHCP offer is received, an IP address gets assigned
to the port (for example, ethernet interface 1/1/1) on which the DHCP offer is
received. No more DHCP offers are accepted on other ports at this point. If a
virtual ethernet (VE) port is configured on the default VLAN, that VE can act
as the
DHCP client if the ip dhcp-client ve default command is
configured. VEs configured on non-default VLANs (user created VLANs) do not act
as
the DHCP client by default. You can change this behavior by designating one of
the
non-default VEs as the DHCP client instead of the default VE.
Therefore, the DHCP client is functional on the following ports based on the configuration:
DHCP Over Default Virtual Ethernet Port (Layer 3 Devices)
The following enhancements mimic the behavior of a Layer 2 device when it is running the Layer 3 image:
- The ICX device is managed even during cable movement from one in-band interface port to another.
- Network devices that are connected downstream through an ICX device are managed no matter what ports are connected, as long as the downstream ports belong to the default Virtual Ethernet port.
- Using DHCP, acquiring an IP address or upgrading the configuration uses zero-touch provisioning.
- By default, the ICX device allows traffic to pass across all ports (reachability).
- A single MAC address per system is used for IP discovery, which allows the same IP address to be used all the time.
Default Virtual Ethernet Port Creation (Layer 3 Devices)
The DHCP server is reachable through a physical port, and, if option 43 VSI is configured on the DHCP server, DHCP server exchange option 43 VSI, “Create default VE” [not case-sensitive], is sent through a DHCPACK message. A RUCKUS device configured as a DHCP client matches the VSI string and creates the default Virtual Ethernet port.
If Virtual Ethernet port creation is successful, the IP address that is acquired through the physical port is released, and an IP address will be re-acquired through the default Virtual Ethernet port.
If default Virtual Ethernet port creation fails, the IP address acquired will be assigned to the physical interface port or ports connecting the DHCP server if the connecting ports are Layer 3 ports.
Possible Reasons for Failure of Virtual Ethernet Port Creation
The member ports of the default VLAN are queried to check for certain configurations. If any of the items are found, default Virtual Ethernet creation fails without other conditions being checked. The following configured items result in failure: