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Figure 33. Client and Server Messaging
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 operating
system (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 configure IP source
address validation on a member port of a virtual local area network (VLAN) and then attempt to apply
an access list to the VLAN, the system displays the first line in the following message. If you first apply
an ACL to a VLAN and then attempt 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 configured L2 ports, any IP ACL,
MAC ACL, or DHCP source address validation ACL does not block DHCP packets.
• The Dell Networking OS 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
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. The system displays
an error message for configurations that exceed the allocated memory.
• The MXL 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 BMP (Bare Metal Provisioning) mode, it is not able to reach
the DHCP server, resulting in BMP failure.
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Dynamic Host Configuration Protocol (DHCP)