How do you calculate a subnet?

Start with an IP address and its prefix length (for example /24). The prefix says how many leading bits are the network portion; the remaining bits are host bits. Set every host bit to 0 to get the network address and to 1 to get the broadcast address. The addresses in between (minus those two on IPv4) are the usable host range. From the prefix you also derive the subnet mask and the total number of addresses (2 raised to the number of host bits). A subnet calculator does all of this instantly: type a network in CIDR or IP-and-mask form and it returns the network, broadcast, host range, mask and host count.

What is 255.255.255.0 in subnet mask?

255.255.255.0 is the IPv4 subnet mask for a /24 network. In binary it is 24 ones followed by 8 zeros, so the first three octets identify the network and the last octet identifies the host. A /24 holds 256 total addresses, of which 254 are usable for hosts. The first is the network address and the last is the broadcast address. It is the most common mask for home and small-office LANs, such as 192.168.1.0/24.

What is the subnet mask of 192.168.1.1 /24?

For 192.168.1.1/24 the subnet mask is 255.255.255.0 and the wildcard mask is 0.0.0.255. The /24 prefix means the first 24 bits are the network portion. So the network address is 192.168.1.0 and the broadcast address is 192.168.1.255, leaving a usable host range of 192.168.1.1 to 192.168.1.254, 254 addresses in total.

How many hosts are in a /26 subnet mask?

A /26 subnet has 64 total addresses (2^6, since 32 − 26 = 6 host bits) and 62 usable host addresses after subtracting the network and broadcast addresses. Its subnet mask is 255.255.255.192 and its wildcard mask is 0.0.0.63. A /26 is a common choice when you need to split a /24 into four equal subnets.

Can I calculate multiple subnets at once?

Yes: bulk subnet calculation is this calculator's normal mode. Enter one network per line, mixing IPv4 and IPv6 freely, and every line is calculated at the same time: network and broadcast address, usable host range, subnet and wildcard mask, and host count for each subnet in the list. The whole result set exports to CSV or JSON in one click, and a share link reproduces the exact list: useful for documenting an addressing plan, auditing firewall rules, or checking a batch of routes without running them one at a time.

How to calculate an IPv6 subnet?

IPv6 subnetting uses the same prefix idea as IPv4, but with 128-bit addresses written in hexadecimal. Pick a prefix length such as /48 or /64: the bits before it are the network/subnet portion and the bits after it form the interface identifier. Set the interface bits to zero for the first address in the block. Because IPv6 has no broadcast address and no reserved network or host addresses, every address in a prefix is usable. The number of addresses is 2 raised to (128 − prefix). A /64 (the standard size for a single LAN) holds 18,446,744,073,709,551,616 addresses.

What is the subnet in IPv6?

A subnet in IPv6 is a range of addresses that share a common prefix, identified by a prefix length after a slash (for example 2001:db8:abcd:1234::/64). The prefix is the network portion; the remaining bits form the interface identifier for individual hosts. The universally recommended subnet size for a single link is /64. Larger allocations such as /48 or /56 are typically assigned to a whole site and then divided into many /64 subnets.

How many subnets are in IPv6?

It depends on the size of your allocation and the subnet size you choose. Each extra bit of prefix length doubles the number of subnets. Dividing a /48 into standard /64 subnets gives 2^(64−48) = 65,536 subnets; a /56 into /64s gives 256 subnets. In theory the entire IPv6 space split into /64s yields 2^64 subnets (about 18 quintillion) which is why IPv6 address exhaustion is not a practical concern.

What is my IPv6 subnet prefix length?

Your IPv6 subnet prefix length is the number after the slash in your address, such as the 64 in 2001:db8::1/64. It states how many leading bits are the network/subnet portion, and on most end devices and LANs it is /64. To find it, check your router or interface configuration, or paste your IPv6 address into a subnet calculator. It reports the prefix length along with the network range and the exact address count.

What is a subnet calculator?

A subnet calculator is a tool that takes an IP network and instantly works out its addressing details, so you don't have to do binary math by hand. Enter a block in CIDR notation, IPv6 shorthand or IP-and-mask form and it returns the network address, broadcast address, usable host range, subnet mask, wildcard mask and host count for both IPv4 and IPv6. It is used by network engineers, students and IT admins to plan networks, size subnets and verify configurations quickly and accurately.

Subnet Calculator: IPv4 & IPv6 CIDR, VLSM and route aggregation

Paste one network or a hundred. Every line returns its network and broadcast address, usable host range, subnet and wildcard mask, host count and address type, recalculated as you type, then exports to CSV or JSON.

Bulk modeone network per line, IPv4 and IPv6 mixed freely, every line calculated at once, not one subnet at a time.
Exact IPv6 maths128-bit integer arithmetic, so a /48 or /64 reports its true address count instead of an approximation.
VLSM splitterdivides a parent block into right-sized child subnets from a list of host counts, packed largest-first.
CIDR aggregationcollapses a route list into the fewest supernets covering exactly the same addresses.
CSV, JSON and share linksexport the whole result table, or send a link that reloads the exact same list.
Nothing leaves your browserall maths runs client-side. No upload, no account, and it keeps working offline.

Also here: an access list matcher for Cisco and Juniper ACLs, MAC address lookup for resolving hardware vendors in bulk, and a data unit converter for bits, bytes and transfer times.

Subnet calculator

Enter one or more networks in CIDR (10.0.0.0/24), IPv6, or IP + mask form. For each one you get the network and broadcast address, the usable host range, the mask, and how many hosts it holds, recalculated the instant you type.

Results

3 networks · updates live

Subnet mask	Wildcard mask	Usable range	Usable hosts	Type
255.255.255.0	0.0.0.255	192.168.1.1 - 192.168.1.254	254	Private
255.0.0.0	0.255.255.255	10.0.0.1 - 10.255.255.254	16,777,214	Private
ffff:ffff:ffff::	::ffff:ffff:ffff:ffff:ffff	2001:db8::1 - 2001:db8:0:ffff:ffff:ffff:ffff:fffe	≈1.20 × 10²⁴	Documentation

192.168.1fixed by the prefix64split inside this octet0host space/26prefix length

3 networks2 IPv4, 16,777,472 addresses1 IPv6, ≈1.20 × 10²⁴ addresses0 errors

VLSM subnet splitter

Split one big block into smaller subnets sized to fit each team or link. List how many hosts each subnet needs and it allocates the smallest block that fits, largest-first, so address space isn't wasted. If the base block is too small to hold everything, it tells you.

Allocation

4 subnets packed largest-first

Label	Requested	Allocated CIDR	Usable range	Usable hosts
Sales	50	192.168.1.0/26	192.168.1.1 - 192.168.1.62	62
Engineering	20	192.168.1.64/27	192.168.1.65 - 192.168.1.94	30
Wi-Fi guests	10	192.168.1.96/28	192.168.1.97 - 192.168.1.110	14
Router link	2	192.168.1.112/30	192.168.1.113 - 192.168.1.114	2

IP address pool reference

The reserved IPv4 and IPv6 ranges, with what each one is for and whether it routes on the public internet. Select any block to load it into the calculator above. Values are taken from the IANA special-purpose address registries.

Private / internal

addresses	purpose	reference
16,777,216	Private-UseInternal networks. The largest RFC 1918 block, usual choice for data centres and large campuses.	RFC 1918not routed
1,048,576	Private-UseInternal networks. Covers 172.16.0.0 to 172.31.255.255, which is the range most often mis-stated as 172.16 to 172.16.	RFC 1918not routed
65,536	Private-UseInternal networks. The default on home and small office routers.	RFC 1918not routed
≈2.65 × 10³⁶	Unique-LocalIPv6 equivalent of RFC 1918. In practice only fd00::/8 is used, with a randomly generated 40-bit global ID; fc00::/8 is unassigned.	RFC 4193not routed

Shared address space

block	addresses	purpose	reference
	4,194,304	Shared Address SpaceCarrier-grade NAT between subscriber and provider. Not private space: do not use it as extra RFC 1918 room, because your ISP may already be using it.	RFC 6598not routed

Loopback

block	addresses	purpose	reference
	16,777,216	LoopbackThe host itself. The whole /8 loops back, not just 127.0.0.1.	RFC 1122not routed
	1	Loopback AddressThe host itself. IPv6 spends a single address here rather than a whole block.	RFC 4291not routed

Link-local

block	addresses	purpose	reference
	65,536	Link LocalSelf-assigned when DHCP fails (APIPA). An address from here usually means the DHCP server did not answer.	RFC 3927not routed
	≈3.32 × 10³⁵	Link-Local UnicastAutomatically configured on every IPv6 interface and required for neighbour discovery. Always present, never routed off the link.	RFC 4291not routed

Multicast

block	addresses	purpose	reference
	268,435,456	MulticastIPv4 multicast, the old class D. 224.0.0.0/24 is link-local control traffic such as OSPF and VRRP.	RFC 5771not routed
	≈1.32 × 10³⁶	MulticastIPv6 multicast. The next 4 bits are flags and the 4 after that are scope, so ff02:: is link-local and ff0e:: is global.	RFC 4291not routed

Documentation and examples

addresses	purpose	reference
256	Documentation (TEST-NET-1)Examples and documentation. Safe to print, never routed.	RFC 5737not routed
256	Documentation (TEST-NET-2)Second documentation block, for examples needing two distinct networks.	RFC 5737not routed
256	Documentation (TEST-NET-3)Third documentation block.	RFC 5737not routed
≈7.92 × 10²⁸	DocumentationThe IPv6 documentation prefix, seen in nearly every IPv6 example ever written.	RFC 3849not routed
≈3.24 × 10³²	DocumentationAdded in 2024 because a single /32 was too small for realistic multi-site examples.	RFC 9637not routed

Globally routable

block	addresses	purpose	reference
	≈4.25 × 10³⁷	Global UnicastThe whole publicly routable IPv6 range. Every address an RIR assigns comes from here, which is one eighth of the address space.	RFC 4291routes globally

IPv4 / IPv6 transition

addresses	purpose	reference
4,294,967,296	IPv4-mapped AddressCarries an IPv4 address inside an IPv6 socket, so ::ffff:192.0.2.1 is 192.0.2.1. Appears in logs on dual-stack hosts.	RFC 4291not routed
4,294,967,296	IPv4-IPv6 TranslationThe well-known prefix for NAT64, letting IPv6-only clients reach IPv4 servers.	RFC 6052routes globally
≈5.19 × 10³³	6to4Legacy automatic tunnelling. Deprecated in practice; reachability depends on a relay.	RFC 3056depends on relay
≈7.92 × 10²⁸	TeredoTunnels IPv6 over UDP through NAT. Reachability depends on the relay.	RFC 4380depends on relay

Benchmarking

block	addresses	purpose	reference
	131,072	BenchmarkingReserved for testing network devices. Traffic must not leave the test rig.	RFC 2544not routed
	≈1.20 × 10²⁴	BenchmarkingIPv6 equivalent for device testing.	RFC 5180not routed

Other reserved

addresses	purpose	reference
16,777,216	This networkSource address only, and only before the host knows its own address. 0.0.0.0/32 alone means this host.	RFC 791not routed
268,435,456	ReservedThe old class E. Reserved indefinitely and dropped by most stacks, so it is not the spare space it looks like.	RFC 1112not routed
1	Limited BroadcastBroadcast to the local link only. Never forwarded by a router.	RFC 8190not routed
256	IETF Protocol AssignmentsReserved for protocol machinery, including the 192.0.0.0/29 DS-Lite range.	RFC 6890not routed
1	Unspecified AddressNo address yet. Seen as the source during duplicate address detection.	RFC 4291not routed
≈5.19 × 10³³	Segment Routing (SRv6) SIDsSegment identifiers for SRv6, allocated in 2024. Forwardable inside an operator's domain but not globally reachable.	RFC 9602not routed
≈1.84 × 10¹⁹	Discard-Only Address BlockA managed black hole: routes here are meant to be discarded, which is used for remotely triggered filtering.	RFC 6666not routed

TCP and UDP port reference

133 ports engineers actually look up, with the IANA service name, what the port is used for in practice, and a warning where the protocol sends credentials in the clear. Search by number, by service, or by what a firewall log called it.

Search ports

133 of 133 ports

Web and proxies8

port	proto	service	used for
80	tcp/udp/sctp	httpWorld Wide Web HTTP	HTTPUnencrypted. Use 443 (HTTPS) in production.
443	tcp/udp/sctp	httpshttp protocol over TLS/SSL	HTTPS
631	tcp/udp	ippIPP (Internet Printing Protocol)	IPP printing
1080	tcp/udp	socksSocks	SOCKS proxy
3128	tcp/udp	ndl-aasActive API Server Port	Squid proxynot the IANA assignment
8080	tcp/udp	http-altHTTP Alternate (see port 80)	HTTP alternateCommon for proxies, app servers and containers behind a reverse proxy.
8443	tcp/udp	pcsync-httpsPCsync HTTPS	HTTPS alternatenot the IANA assignmentWidely used as a second HTTPS port; IANA assigns it to PCsync.
9100	tcp/udp	pdl-datastreamPrinter PDL Data Stream	Printer raw / JetDirect

Mail7

port	proto	service	used for
25	tcp/udp	smtpSimple Mail Transfer	SMTP relayUnencrypted. Use 587 with STARTTLS, or 465 implicit TLS.
110	tcp/udp	pop3Post Office Protocol - Version 3	POP3Unencrypted. Use 995 (POP3S).
143	tcp	imapInternet Message Access Protocol	IMAPUnencrypted. Use 993 (IMAPS).
465	tcp	submissionsMessage Submission over TLS protocol	SMTP submission over TLS
587	tcp/udp	submissionMessage Submission	SMTP submission
993	tcp	imapsIMAP over TLS protocol	IMAP over TLS
995	tcp/udp	pop3sPOP3 over TLS protocol	POP3 over TLS

File transfer and sharing13

port	proto	service	used for
20	tcp/udp/sctp	ftp-dataFile Transfer [Default Data]	FTP dataUnencrypted. Use SFTP over 22, or FTPS on 989/990.
21	tcp/udp/sctp	ftpFile Transfer Protocol [Control]	FTP controlUnencrypted. Use SFTP over 22, or FTPS on 989/990.
69	tcp/udp	tftpTrivial File Transfer	TFTPUnencrypted. No authentication at all. Keep it off routable networks.
139	tcp/udp	netbios-ssnNETBIOS Session Service	NetBIOS sessionLegacy SMB transport.
445	tcp/udp	microsoft-dsMicrosoft-DS	SMB / CIFSWindows file sharing. Never expose to the internet.
548	tcp/udp	afpovertcpAFP over TCP	AFP
873	tcp/udp	rsyncrsync	rsync
989	tcp/udp	ftps-dataftp protocol, data, over TLS/SSL	FTPS data
990	tcp/udp	ftpsftp protocol, control, over TLS/SSL	FTPS control
2049	tcp/udp/sctp	nfsNetwork File System - Sun Microsystems	NFS
3260	tcp/udp	iscsi-targetiSCSI port	iSCSI target
3690	tcp/udp	svnSubversion	Subversion
9418	tcp/udp	gitgit pack transfer service	Git protocolUnencrypted. Unauthenticated and unencrypted; prefer SSH or HTTPS.

Remote access and management9

port	proto	service	used for
22	tcp/udp/sctp	sshThe Secure Shell (SSH) Protocol	SSH / SFTP / SCP
23	tcp/udp	telnetTelnet	TelnetUnencrypted. Credentials sent in the clear. Use 22 (SSH).
623	udp	asf-rmcpASF Remote Management and Control Protocol	IPMI / BMCOut-of-band server management. Keep it on an out-of-band management network.
2000	tcp/udp	cisco-sccpCisco SCCP	Cisco SCCP
3389	tcp/udp	ms-wbt-serverMS WBT Server	RDPMicrosoft Remote Desktop. A top ransomware entry point when exposed.
5555	tcp/udp	personal-agentPersonal Agent	Android ADBnot the IANA assignmentIANA assigns this to personal-agent.
5900	tcp/udp	rfbRemote Framebuffer	VNCUnencrypted. VNC auth is weak; tunnel it over SSH.
5985	tcp/udp	wsmanWBEM WS-Management HTTP	WinRM HTTPUnencrypted. Use 5986 for WinRM over TLS.
5986	tcp/udp	wsmansWBEM WS-Management HTTP over TLS/SSL	WinRM HTTPS

Directory and authentication11

port	proto	service	used for
49	tcp/udp	tacacsLogin Host Protocol (TACACS)	TACACS+
88	tcp/udp	kerberosKerberos	Kerberos
113	tcp/udp	authAuthentication Service	ident
389	tcp/udp	ldapLightweight Directory Access Protocol	LDAPUnencrypted. Use 636 (LDAPS) or StartTLS.
464	tcp/udp	kpasswdkpasswd	Kerberos password change
636	tcp/udp	ldapsldap protocol over TLS/SSL (was sldap)	LDAPS
1645	tcp/udp	sightlineSightLine	RADIUS (legacy)not the IANA assignmentPre-standard RADIUS port, still seen on older kit. IANA assigns it to SightLine.
1812	tcp/udp	radiusRADIUS	RADIUS authentication
1813	tcp/udp	radius-acctRADIUS Accounting	RADIUS accounting
3268	tcp/udp	msft-gcMicrosoft Global Catalog	Global Catalog
3269	tcp/udp	msft-gc-sslMicrosoft Global Catalog with LDAP/SSL	Global Catalog over TLS

Databases and caches10

port	proto	service	used for
1433	tcp/udp	ms-sql-sMicrosoft-SQL-Server	Microsoft SQL Server
1434	tcp/udp	ms-sql-mMicrosoft-SQL-Monitor	SQL Server Browser
1521	tcp/udp	ncube-lmnCube License Manager	Oracle DB listenernot the IANA assignmentUniversally used by Oracle; IANA assigns it to nCube License Manager.
2379	tcp	etcd-clientetcd client communication	etcd client
3306	tcp/udp	mysqlMySQL	MySQL / MariaDB
5432	tcp/udp	postgresqlPostgreSQL Database	PostgreSQL
6379	tcp	redisAn advanced key-value cache and store	RedisNo auth by default in older builds. Never expose it.
9200	tcp/udp	wap-wspWAP connectionless session service	Elasticsearch HTTPnot the IANA assignmentIANA assigns it to WAP session service.
11211	tcp/udp	memcacheMemory cache service	MemcachedUDP mode has been abused for reflection attacks; disable it.
27017	tcp	mongodbMongo database system	MongoDB

Core network services21

port	proto	service	used for
53	tcp/udp	domainDomain Name Server	DNSUDP for queries, TCP for zone transfers and large responses.
67	tcp/udp	bootpsBootstrap Protocol Server	DHCP server
68	tcp/udp	bootpcBootstrap Protocol Client	DHCP client
111	tcp/udp	sunrpcSUN Remote Procedure Call	RPC portmapperFronts NFS and other RPC services.
123	tcp/udp	ntpNetwork Time Protocol	NTP
135	tcp/udp	epmapDCE endpoint resolution	MS RPC endpoint mapper
137	tcp/udp	netbios-nsNETBIOS Name Service	NetBIOS name
138	tcp/udp	netbios-dgmNETBIOS Datagram Service	NetBIOS datagram
161	tcp/udp	snmpSNMP	SNMPUnencrypted. v1 and v2c community strings are plaintext. Use SNMPv3.
162	tcp/udp	snmptrapSNMPTRAP	SNMP trap
427	tcp/udp	svrlocServer Location	SLP
514	udp	syslog	SyslogUDP 514 is syslog; TCP 514 is the old rsh shell service.
546	tcp/udp	dhcpv6-clientDHCPv6 Client	DHCPv6 client
547	tcp/udp	dhcpv6-serverDHCPv6 Server	DHCPv6 server
853	tcp/udp	domain-sDNS query-response protocol run over TLS	DNS over TLS
1900	tcp/udp	ssdpSSDP	SSDP / UPnPReflection-attack amplifier. Block inbound at the edge.
3702	tcp/udp	ws-discoveryWeb Service Discovery	WS-Discovery
5353	tcp/udp	mdnsMulticast DNS	mDNS / Bonjour
5355	tcp/udp	llmnrLLMNR	LLMNRFrequently abused for credential relay; disable on Windows networks.
6514	tcp/udp	syslog-tlsSyslog over TLS	Syslog over TLS
7547	tcp/udp	cwmpBroadband Forum CWMP	TR-069 CWMPISP remote management of CPE.

Routing and network control14

port	proto	service	used for
179	tcp/udp/sctp	bgpBorder Gateway Protocol	BGP
520	udp	routerlocal routing process (on site); uses variant of Xerox NS routing information protocol - RIP	RIP
521	tcp/udp	ripngripng	RIPng
646	tcp/udp	ldpLDP	MPLS LDP
830	tcp/udp	netconf-sshNETCONF over SSH	NETCONF over SSH
1985	tcp/udp	hsrpHot Standby Router Protocol	HSRP
2055	tcp/udp	iopIliad-Odyssey Protocol	NetFlownot the IANA assignmentThe conventional NetFlow collector port; IANA assigns it to Iliad-Odyssey.
2152	tcp/udp	gtp-userGTP-User Plane (3GPP)	GTP user plane
3784	tcp/udp	bfd-controlBFD Control Protocol	BFD control
4739	tcp/udp/sctp	ipfixIP Flow Info Export	IPFIX
4789	udp	vxlanVirtual eXtensible Local Area Network (VXLAN)	VXLAN
6081	udp	geneveGeneric Network Virtualization Encapsulation (Geneve)	Geneve
6343	tcp/udp	sflowsFlow traffic monitoring	sFlow
6653	tcp/udp	openflowOpenFlow	OpenFlow

VPN and tunnelling6

port	proto	service	used for
500	tcp/udp	isakmpisakmp	IKE / ISAKMP
1194	tcp/udp	openvpnOpenVPN	OpenVPN
1701	tcp/udp	l2tpl2tp	L2TP
1723	tcp/udp	pptppptp	PPTPUnencrypted. PPTP is cryptographically broken. Use IPsec or WireGuard.
4500	tcp/udp	ipsec-nat-tIPsec NAT-Traversal	IPsec NAT traversal
51820	udp	not registered	WireGuardThe WireGuard default. Not registered with IANA.

Messaging and queues9

port	proto	service	used for
1883	tcp/udp	mqttMessage Queuing Telemetry Transport Protocol	MQTTUnencrypted. Use 8883 for MQTT over TLS.
4369	tcp/udp	epmdErlang Port Mapper Daemon	Erlang EPMD
5222	tcp	xmpp-clientXMPP Client Connection	XMPP client
5269	tcp	xmpp-serverXMPP Server Connection	XMPP server
5671	tcp/udp	amqpsamqp protocol over TLS/SSL	AMQP over TLS
5672	tcp/udp/sctp	amqpAMQP	AMQP / RabbitMQ
6667	tcp	ircuIRCU	IRC
8883	tcp/udp	secure-mqttSecure MQTT	MQTT over TLS
9092	tcp/udp	XmlIpcRegSvcXml-Ipc Server Reg	Apache Kafkanot the IANA assignmentThe Kafka default; IANA assigns it to Xml-Ipc.

Containers and orchestration6

port	proto	service	used for
2181	tcp/udp	eforwardeforward	Apache ZooKeepernot the IANA assignmentThe ZooKeeper default; IANA assigns it to eforward.
2375	tcp	dockerDocker REST API (plain text)	Docker APIUnencrypted. Unauthenticated root-equivalent access. Never expose.
2376	tcp	docker-sDocker REST API (ssl)	Docker API over TLS
6443	tcp/udp	sun-sr-httpsService Registry Default HTTPS Domain	Kubernetes API servernot the IANA assignmentThe kube-apiserver default; IANA assigns it to Sun Service Registry.
10050	tcp/udp	zabbix-agentZabbix Agent	Zabbix agent
10051	tcp/udp	zabbix-trapperZabbix Trapper	Zabbix trapper

Voice and media5

port	proto	service	used for
554	tcp/udp	rtspReal Time Streaming Protocol (RTSP)	RTSP
3478	tcp/udp	stunSession Traversal Utilities for NAT (STUN) port	STUN / TURN
5060	tcp/udp/sctp	sipSIP	SIPUnencrypted. Use 5061 for SIP over TLS.
5061	tcp/udp/sctp	sipsSIP-TLS	SIP over TLS
32400	tcp	plexPlex multimedia	Plex

Industrial and SCADA5

port	proto	service	used for
102	tcp/udp	iso-tsapISO-TSAP Class 0	S7comm / ISO-TSAP
502	tcp/udp	mbapModbus Application Protocol	Modbus TCPUnencrypted. No authentication in the protocol. Segment it.
2222	tcp/udp	EtherNet-IP-1EtherNet/IP I/O IANA assigned this well-formed service name as a replacement for "EtherNet/IP-1".	EtherNet/IP implicit
20000	tcp/udp/sctp	dnpDNP	DNP3
44818	tcp/udp	EtherNet-IP-2EtherNet/IP messaging IANA assigned this well-formed service name as a replacement for "EtherNet/IP-2".	EtherNet/IP explicit

Legacy and diagnostics9

port	proto	service	used for
7	tcp/udp	echoEcho	Echo
13	tcp/udp	daytimeDaytime	Daytime
19	tcp/udp	chargenCharacter Generator	ChargenReflection-attack amplifier. Disable it.
37	tcp/udp	timeTime	Time
43	tcp/udp	nicnameWho Is	WHOIS
79	tcp/udp	fingerFinger	Finger
119	tcp/udp	nntpNetwork News Transfer Protocol	NNTP
194	tcp/udp	ircInternet Relay Chat Protocol	IRC (original)
515	tcp/udp	printerspooler	LPD print

Service names and descriptions come from the IANA Service Name and Transport Protocol Port Number Registry. Where the name in common use is not what IANA assigns, both are shown.

Also for subnetting

ReferenceSubnet cheat sheetEvery CIDR prefix with its mask, wildcard and host count — /0 to /32 for IPv4 and /0 to /128 for IPv6. Filterable, and it prints on one page.PracticeSubnetting questionsUnlimited generated questions for CCNA and Network+, marked instantly, with the block-size working shown every time.