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Implementation Information
The following describes DHCP implementation.
• Dell Networking implements DHCP based on RFC 2131 and RFC 3046.
• IP source address validation is a sub-feature of DHCP Snooping; the Dell Networking OS uses access control lists (ACLs) internally to
implement this feature and as such, you cannot apply ACLs to an interface which has IP source address validation. If you congure IP
source address validation on a member port of a virtual local area network (VLAN) and then apply an access list to the VLAN, the
system displays the rst line in the following message. If you rst apply an ACL to a VLAN and then enable IP source address validation
on one of its member ports, the system displays the second line in the following message.
% Error: Vlan member has access-list configured.
% Error: Vlan has an access-list configured.
NOTE: If you enable DHCP Snooping globally and you have any congured L2 ports, any IP ACL, MAC ACL, or DHCP
source address validation ACL does not block DHCP packets.
• The system provides 40K dhcp binding entries that can be divided between leased addresses and excluded addresses. By
extension, the maximum number of pools you can congure depends on the subnet mask that you give to each pool. For example, if all
pools were congured for a /24 mask, the total would be 40000/253 (approximately 158). If the subnet is increased, more pools can be
congured. The maximum subnet that can be congured for a single pool is /17. The system displays an error message for
congurations that exceed the allocated memory.
• The switch supports 4K DHCP Snooping entries.
• All platforms support Dynamic ARP Inspection on 16 VLANs per system. For more information, refer to Dynamic ARP Inspection.
NOTE: If the DHCP server is on the top of rack (ToR) and the VLTi (ICL) is down due to a failed link, when a VLT node is
rebooted in JumpStart mode, it is not able to reach the DHCP server, resulting in bare metal provisioning (BMP) failure.
Congure the System to be a DHCP Server
A DHCP server is a network device that has been programmed to provide network conguration parameters to clients upon request.
Servers typically serve many clients, making host management much more organized and ecient.
The following table lists the key responsibilities of DHCP servers.
Table 26. DHCP Server Responsibilities
DHCP Server Responsibility Description
Address Storage and Management DHCP servers are the owners of the addresses used by DHCP
clients. The server stores the addresses and manages their use,
keeping track of which addresses have been allocated and which
are still available.
Conguration Parameter Storage and Management DHCP servers also store and maintain other parameters that are
sent to clients when requested. These parameters specify in detail
how a client is to operate.
Lease Management DHCP servers use leases to allocate addresses to clients for a
limited time. The DHCP server maintains information about each of
the leases, including lease length.
Responding To Client Requests DHCP servers respond to dierent types of requests from clients,
primarily, granting, renewing, and terminating leases.
Providing Administration Services DHCP servers include functionality that allows an administrator to
implement policies that govern how DHCP performs its other tasks.
NOTE: DHCP server is not supported on VLT.
348 Dynamic Host Conguration Protocol (DHCP)