Value,Name,Status,Reference
0,Reserved,,[RFC6891]
1,LLQ,Optional,[RFC8764]
2,UL,On-hold,[http://files.dns-sd.org/draft-sekar-dns-ul.txt]
3,NSID,Standard,[RFC5001]
4,Reserved,,[draft-cheshire-edns0-owner-option]
5,DAU,Standard,[RFC6975]
6,DHU,Standard,[RFC6975]
7,N3U,Standard,[RFC6975]
8,edns-client-subnet,Optional,[RFC7871]
9,EDNS EXPIRE,Optional,[RFC7314]
10,COOKIE,Standard,[RFC7873]
11,edns-tcp-keepalive,Standard,[RFC7828]
12,Padding,Standard,[RFC7830]
13,CHAIN,Standard,[RFC7901]
14,edns-key-tag,Optional,[RFC8145]
15,Extended DNS Error,Standard,[RFC8914]
16,EDNS-Client-Tag,Optional,[draft-bellis-dnsop-edns-tags]
17,EDNS-Server-Tag,Optional,[draft-bellis-dnsop-edns-tags]
18-20291,Unassigned,,
20292,Umbrella Ident,Optional,[https://developer.cisco.com/docs/cloud-security/#!integrating-network-devices/rdata-description][Cisco_CIE_DNS_team]
20293-26945,Unassigned,,
26946,DeviceID,Optional,[https://developer.cisco.com/docs/cloud-security/#!network-devices-getting-started/response-codes][Cisco_CIE_DNS_team]
26947-65000,Unassigned,,
65001-65534,Reserved for Local/Experimental Use,,[RFC6891]
65535,Reserved for future expansion,,[RFC6891]