Reference Guide

336 | Dynamic Host Configuration Protocol (DHCP)
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Implementation Information
• The Dell Networking implementation of DHCP is based on RFC 2131 and RFC 3046.
• IP Source Address Validation is a sub-feature of DHCP Snooping; FTOS uses ACLs internally to
implement this feature and as such, you cannot apply ACLs to an interface which has IP Source
Address Validation. If you configure IP Source Address Validation on a member port of a VLAN and
then attempt to apply a access list to the VLAN, FTOS displays the first line in Message 1. If you first
apply an ACL to a VLAN and then attempt enable IP Source Address Validation on one of its member
ports, FTOS displays the second line in Message 1.
• FTOS provides 40K entries that can be divided between leased addresses and excluded addresses. By
extension, the maximum number of pools you can configure depends on the on the subnet mask that
you give to each pool. For example, if all pools were configured for a /24 mask, the total would be
40000/253 (approximately 158). If the subnet is increased, more pools can be configured. The
maximum subnet that can be configured for a single pool is /17. FTOS displays an error message for
configurations that exceed the allocated memory.
• The S5000 supports 4K DHCP Snooping entries.
• The S5000 supports Dynamic ARP Inspection on 16 VLANs per system. Refer to Dynamic ARP
Inspection.
Configuration Tasks
• Configuring the System to be a DHCP Server
• Configuring the System to be a Relay Agent
• Configuring Secure DHCP
Configuring the System to be a DHCP Server
A DHCP server is a network device that has been programmed to provide network configuration
parameters to clients upon request. Servers typically serve many clients, making host management much
more organized and efficient.
The key responsibilities of DHCP servers are:
Message 1 DHCP Snooping with VLAN ACL Compatibility Error
% Error: Vlan member has access-list configured.
% Error: Vlan has an access-list configured.
Note: If DHCP snooping is enabled globally and any L2 port is configured, any IP ACL,MAC ACL, or
DHCP Source-Address validation ACL won't block DHCP packets .
Note: If the DHCP server is located on the ToR and the VLTi (ICL) is down due to a failed link when a VLT
node is rebooted in JumpStart mode, it will not be able to reach the DHCP server, resulting in BMP failure.