b09f51b5_HCP_Overview__Support____Cisco__DHCP_Option_Name
[DHCP Option Code] 15 [Description] Specifies the domain name that the client should use when resolving hostnames via the Domain Name System. [DHCP Option Name] 
Domain name option
IP Addressing: DHCP Configuration Guide, Cisco IOS XE Release 3S (Cisco ASR 1000) - DHCP Overview [Support] - Cisco