Calculators

Subnet Calculator

Calculate network, broadcast, host range from any IP/CIDR

New to subnetting? An IP address has two parts: the network (your neighborhood) and the host (your house number). The CIDR number after the slash (e.g. /24) tells you how many bits are the network part. Try 192.168.1.0 with CIDR 24, or paste 10.0.0.0/8 into the address box.

IP Address

CIDR / Prefix Length

Network Address

192.168.1.0

Broadcast Address

192.168.1.255

Subnet Mask

255.255.255.0

Wildcard Mask

0.0.0.255

First Usable

192.168.1.1

Last Usable

192.168.1.254

Usable Hosts

254

Total Addresses

256

IP Class

IP Type

Private (RFC 1918)

Binary Mask

11111111.11111111.11111111.00000000

CIDR Notation

/24

CIDR	Subnet Mask	Wildcard	Usable Hosts	Note
/32	255.255.255.255	0.0.0.0	1	Host route
/31	255.255.255.254	0.0.0.1	2	P2P link
/30	255.255.255.252	0.0.0.3	2	P2P link
/29	255.255.255.248	0.0.0.7	6	Small
/28	255.255.255.240	0.0.0.15	14	Small
/27	255.255.255.224	0.0.0.31	30	Workgroup
/26	255.255.255.192	0.0.0.63	62	Dept.
/25	255.255.255.128	0.0.0.127	126	Half C
/24	255.255.255.0	0.0.0.255	254	Standard LAN
/23	255.255.254.0	0.0.1.255	510
/22	255.255.252.0	0.0.3.255	1,022
/21	255.255.248.0	0.0.7.255	2,046
/20	255.255.240.0	0.0.15.255	4,094	Large
/19	255.255.224.0	0.0.31.255	8,190
/18	255.255.192.0	0.0.63.255	16,382
/17	255.255.128.0	0.0.127.255	32,766
/16	255.255.0.0	0.0.255.255	65,534	Class B
/8	255.0.0.0	0.255.255.255	16.7M	Class A

Private IP Ranges (RFC 1918)

Class	Range	CIDR	Hosts
A	10.0.0.0 – 10.255.255.255	/8	16,777,214
B	172.16.0.0 – 172.31.255.255	/12	1,048,574
C	192.168.0.0 – 192.168.255.255	/16	65,534

Usable hosts = 2ⁿ − 2 (where n = host bits). Subtract 2 for network and broadcast addresses.

IPv4 Multicast Address Space (224.0.0.0/4)

Multicast uses Class D addresses — 224.0.0.0 through 239.255.255.255. Unlike unicast (one-to-one) or broadcast (one-to-all), multicast delivers to a subscribed group. Routers use IGMP locally and PIM between routers to manage group membership and distribution trees.

Range	Block Name	RFC / Scope	Notes
224.0.0.0 – 224.0.0.255	Link-Local Control	RFC 5771	Never forwarded by routers. Protocol-use only (OSPF, EIGRP, PIM, VRRP…)
224.0.1.0 – 224.0.1.255	Internetwork Control	IANA	Globally routable control traffic (NTP, RP-announce, etc.)
224.0.2.0 – 224.0.255.255	AD-HOC Block I	RFC 5771	Globally routable, miscellaneous assigned addresses
224.1.0.0 – 231.255.255.255	Global Scope (General)	RFC 5771	Public multicast streams, applications, conferencing
232.0.0.0/8	Source-Specific Multicast (SSM)	RFC 4607	Receiver specifies both group and source — no RP needed. Preferred for broadcast/AV delivery.
233.0.0.0/8	GLOP Addressing	RFC 3180	ASN embedded in 2nd/3rd octets. AS 65000 = 233.253.232.0/24. Deprecated for new deployments.
234.0.0.0/8	Unicast-Prefix-Based	RFC 6034	Derived from unicast prefix — avoids manual coordination.
239.0.0.0/8	Administratively Scoped	RFC 2365	Private multicast — like RFC 1918 for unicast. Use freely inside your org; won't leak to Internet.

Well-Known Link-Local Addresses (224.0.0.x)

These are never forwarded by routers. TTL = 1 by default. Essential for protocol operation on directly connected segments.

Address	Protocol / Use	Notes
224.0.0.1	All Hosts (All Systems)	Every multicast-capable host on the segment
224.0.0.2	All Routers	All multicast routers on the segment
224.0.0.4	DVMRP Routers	Distance Vector Multicast Routing Protocol (legacy)
224.0.0.5	OSPF — All Routers	All OSPF routers (Hello, LSAs)
224.0.0.6	OSPF — DR/BDR	Designated Router / Backup DR only
224.0.0.9	RIPv2	All RIPv2 routers
224.0.0.10	EIGRP	All EIGRP routers — Hello packets
224.0.0.12	DHCP Relay (Bootstrap)	BOOTP/DHCP server discovery
224.0.0.13	PIM — All PIM Routers	Protocol Independent Multicast Hellos
224.0.0.18	VRRP	Virtual Router Redundancy Protocol
224.0.0.19–21	IS-IS over IP	Intermediate System to Intermediate System
224.0.0.22	IGMPv3 Reports	Membership reports sent to this address
224.0.0.107	PTPv2 / IEEE 1588	PTP peer-delay messages (P2P transport)
224.0.1.1	NTP — Network Time Protocol	Globally routable NTP multicast
224.0.1.129	PTPv2 / IEEE 1588	PTP primary / Sync messages (E2E transport)

Broadcast & AV Multicast Addressing

Broadcast and AV-over-IP standards rely heavily on multicast within the 239.0.0.0/8 administratively scoped block and, increasingly, SSM 232.0.0.0/8. Below are common allocations used in broadcast facilities.

Address / Range	Standard / Protocol	Notes
239.0.0.0/8	Administratively Scoped (General)	Use this block for all internal facility multicast. Sub-allocate by site or service.
239.255.255.250	SSDP / UPnP	Simple Service Discovery Protocol — device discovery
239.255.255.251	mDNS / Bonjour / Avahi	Multicast DNS — zero-config device discovery (port 5353)
239.69.0.0/16	AES67 / RAVENNA (common)	Common facility allocation for AES67 audio streams — not a standard, coordinate internally
239.x.x.x (custom)	SMPTE ST 2110	Video (2110-20), audio (2110-30/31), metadata (2110-40) — assign per stream within your 239/8 block
224.2.0.0/11	SAP / SDP (SDP Announcements)	Session Announcement Protocol — used for MPEG multicast service discovery; 224.2.127.254 = SAP
224.2.127.254	SAP Announcements	Listening address for SAP/SDP stream discovery (VLC auto-detect)
232.0.0.0/8	SSM — Source-Specific Multicast	Preferred for IPTV / AV-over-IP. Receiver joins (S, G) pair — eliminates RP, reduces spoofing risk.

IGMP Versions

Version	RFC	Key Feature	Leave Behavior	Recommendation
IGMPv1	RFC 1112	Basic join. No explicit leave.	Timeout-based (~3 min)	Legacy only
IGMPv2	RFC 2236	Explicit leave group message. Faster leave.	Leave + Last-Member Query (~1–2s)	Acceptable, common
IGMPv3	RFC 3376	Source filtering — supports SSM (S,G) joins. Reports sent to 224.0.0.22.	Explicit include/exclude source lists	Recommended

Multicast MAC Address Mapping

IPv4 multicast addresses map to a corresponding Ethernet MAC address. The OUI 01:00:5E is reserved for IPv4 multicast. Only the low-order 23 bits of the multicast IP are mapped — meaning 32 group addresses share each MAC (bit 25 is not mapped), which can cause unwanted traffic on unmanaged switches.

IP: 239 . 1 . 2 . 100 → Binary low 23 bits: 0000001 . 00000010 . 01100100

MAC: 01:00:5E : 01:02:64 (OUI fixed, last 3 octets from IP low-23)

Formula: Take the last 3 octets of the multicast IP → zero out the MSB of the first → append to 01:00:5E. Example: 239.1.2.100 → 01:00:5E:01:02:64

IPv6 Multicast (FF00::/8)

IPv6 has no broadcast — multicast replaces it. All IPv6 multicast addresses begin with FF. The second byte encodes flags and scope. There is no separate IGMP; IPv6 uses MLD (Multicast Listener Discovery) — MLDv1 ≈ IGMPv2, MLDv2 ≈ IGMPv3 with SSM support.

Address	Scope	Purpose
FF01::1	Interface-local	All nodes (same interface only)
FF01::2	Interface-local	All routers (same interface only)
FF02::1	Link-local	All nodes on the link
FF02::2	Link-local	All routers on the link
FF02::5	Link-local	OSPFv3 all routers
FF02::6	Link-local	OSPFv3 DR/BDR
FF02::A	Link-local	EIGRP routers
FF02::D	Link-local	PIM routers
FF02::16	Link-local	MLDv2 reports (like IGMPv3)
FF02::1:FF00::/104	Link-local	Solicited-node multicast (NDP / neighbor discovery)
FF05::2	Site-local	All routers in site
FF0E::/16	Global	Globally scoped IPv6 multicast

PIM Modes — Quick Reference

Mode	Tree Type	RP Required?	Best For
PIM-SM	Shared (RPT) + Shortest Path Tree	Yes — Rendezvous Point	Sparse receivers spread across a large network
PIM-DM	Source-based (SPT) — flood & prune	No	Dense receivers, small networks — not recommended at scale
PIM-SSM	Source-specific (S, G) SPT only	No RP needed	IPTV, AV-over-IP, AES67 — preferred in modern broadcast networks
Bidir-PIM	Bidirectional shared tree	Yes — RP is a forwarding point	Many-to-many (video conferencing, trading floors)

Broadcast AV Tip: Use PIM-SSM with IGMPv3 for SMPTE ST 2110 and AES67 — it eliminates the RP as a single point of failure and maps directly to the (S,G) model used by those standards.