Users Guide

ip dhcp-relay vss
Enables the support for the DHCPv4 Virtual Subnet Selection (VSS) option.
Syntax
ip dhcp-relay vss
Parameters None.
Defaults Disabled by default.
Command Mode CONFIGURATION
Usage
Information
After enabling the VSS option, the DHCPv4 virtual subnet selection support gets enabled globally.
Additionally, to send VRF information to the DHCP server, you must configure the VSS type information
on the respective DHCP client facing interfaces.
NOTE: Option-82 must be enabled Globally and at the interface level to activate VSS feature
support.
This command is restricted to netadmin and sysadmin roles users.
Example
OS10(config)# ip dhcp-relay vss
OS10-8986(config)# ip dhcp-relay ?
max-hops Maximum allowable hop count
server-override Enable relay server override sub-option
vss Enable VSS sub-option in relay agent
Supported
Releases
10.5.2 or later
ip dhcp-relay vss-info
Configures the VRF information to be carried in the option 151 field of relay packets to the server which allows the DHCP server
to decide the address pool for IP allocation.
Syntax
ip dhcp-relay vss-info type {0 [ value string]/1 [value 7-octet value]/255}
Parameters
● 0 string - Enter the type as 0 then the VRF name.
● 1 value - Enter the type as 1 then OUI:VRF-Index ,3 bytes OUI:4 bytes VRF_Index
● 255 - Enter the type as 255 for global or default address space.
Defaults No vss-info value is configured on the interface.
Command Mode INTERFACE CONFIGURATION
Usage
Information
The VRF values for subnet selection are sent to the DHCP server in the option 151 field only if ip
dhcp-relay vss-enable is enabled at the Global level. The value of the VRF name must match a
VRF configured on the DHCP server for a DHCP pool. It is not the name of a VRF configured on the local
switch, as a result, no validation is performed.
● To send the VRF information to the DHCP server, set the vss-info type as type-0 or type-1 and
configure the corresponding VRF name string or VRF Octet value, respectively, on the interface.
● If a no value or type-255 is passed as the vss value, the IP address is allocated from the default
address pool of the server corresponding to the link selection subnet.
● The type 0 and type 1 values configured on the client interfaces must contain the server-side
VRF DHCP pool information. It is used by the server to allocate IP address to the clients from the
requested VRF pool. The configured type 0 or type 1 value must be the VRF or VPN ID associated
with the DHCP pool in the server.
You can configure the vss-info on all types of the DHCP client interfaces (Ethernet interface, port-
channel, VLAN, and virtual-network).
NOTE: With VSS enabled, change in the vss-info configuration value at the interface after the
client IP assignment takes effect in the subsequent renew process. If the client receives a NACK, the
client starts the discovery process with the new values.
300 System management