IP Addressing

IP Addressing

Overview

IP Addressing is a fundamental networking concept that provides logical addressing for devices on an IP network. RouterOS provides comprehensive support for both IPv4 and IPv6 addressing, allowing you to configure addresses on interfaces, manage address pools, and control address assignment through DHCP.

This documentation covers the /ip address menu for IPv4 configuration and IPv6 address management, explaining address types, subnetting concepts, and practical RouterOS configurations.

IPv4 Addressing

IPv4 addresses are 32-bit addresses written in dotted-decimal notation (e.g., 192.168.88.1). Each address consists of a network portion and a host portion, determined by the subnet mask.

Address Structure

An IPv4 address is represented as four octets (0-255) separated by dots:

192.168.88.1

The subnet mask determines how many bits represent the network portion:

CIDR Notation	Subnet Mask	Usable Hosts
/24	255.255.255.0	254
/25	255.255.255.128	126
/26	255.255.255.192	62
/27	255.255.255.224	30
/28	255.255.255.240	14
/29	255.255.255.248	6
/30	255.255.255.252	2
/32	255.255.255.255	1 (point-to-point)

Private Address Ranges

RFC 1918 reserves specific address ranges for private networks. These addresses are not routable on the internet and are commonly used for internal networks:

Address Range	CIDR	Start	End
10.0.0.0/8	10.x.x.x	10.0.0.0	10.255.255.255
172.16.0.0/12	172.16.x.x - 172.31.x.x	172.16.0.0	172.31.255.255
192.168.0.0/16	192.168.x.x	192.168.0.0	192.168.255.255

Other Reserved Address Ranges

Range	Description
0.0.0.0/8	This network (RFC 1122)
127.0.0.0/8	Loopback addresses
169.254.0.0/16	Link-local (APIPA)
224.0.0.0/4	Multicast (Class D)
240.0.0.0/4	Reserved (Class E)
255.255.255.255/32	Limited broadcast

Adding IP Addresses

Basic Configuration

Add an IP address to an interface using the /ip address menu:

/ip address add address=192.168.88.1/24 interface=ether1

This assigns the address 192.168.88.1 with a /24 subnet mask (255.255.255.0) to ether1.

Viewing Address Configuration

/ip address print

Output:

Flags: X - disabled, I - invalid, D - dynamic, G - global, P - pending
 #   ADDRESS            NETWORK         INTERFACE         DHCPSERVER
 0 G 192.168.88.1/24   192.168.88.0   ether1

The output shows:

• ADDRESS: The IP address with CIDR prefix
• NETWORK: The network address (first address in subnet)
• INTERFACE: The interface the address is assigned to
• DHCPSERVER: If DHCP server is running on this address

Properties

Property	Description
address	IP address with CIDR notation (e.g., 192.168.88.1/24)
netmask	Subnet mask in dotted decimal (alternative to CIDR)
network	Network address (auto-calculated or explicitly set)
interface	Interface to assign the address to
disabled	Whether the address is disabled
actual-interface	Shows the actual interface (for bridges, VLANs)
dhcp-server	DHCP server that provides addresses from this pool
dynamic	Whether the address was assigned dynamically
publish	Whether to publish this address in routing protocols

Example Configurations

Multiple Addresses on Single Interface

Add multiple addresses to a single interface:

/ip address add address=192.168.88.1/24 interface=ether1
/ip address add address=10.0.0.1/24 interface=ether1

Point-to-Point Links

For point-to-point links, use /32 addresses:

/ip address add address=10.0.0.1/32 network=10.0.0.2 interface=ether1
/ip address add address=10.0.0.2/32 network=10.0.0.1 interface=ether2

Bridge Interface Addressing

Assign an IP address to a bridge:

/ip address add address=192.168.1.1/24 interface=bridge1

Read-only Properties

These properties are automatically calculated and cannot be modified:

Property	Description
dynamic	Address was assigned via DHCP or other dynamic method
invalid	Address configuration is invalid
actual-interface	The actual underlying interface

IPv6 Addressing

IPv6 addresses are 128-bit addresses typically written in hexadecimal notation with colons. RouterOS supports full IPv6 address configuration including link-local, unique local, and global unicast addresses.

Address Types

Link-local Addresses

Link-local addresses (fe80::/10) are automatically generated on all interfaces and are used for local communication only:

/ipv6 address add address=fe80::1/64 interface=ether1

RouterOS automatically generates link-local addresses when an interface is enabled. You can verify:

/ipv6 address print

Unique Local Addresses

Unique local addresses (ULA, fc00::/7) are similar to IPv4 private addresses:

/ipv6 address add address=fd00::1/64 interface=ether1 advertise=no

Global Unicast Addresses

Global unicast addresses are publicly routable addresses assigned by an ISP or through other delegation methods:

/ipv6 address add address=2001:db8::1/64 interface=ether1

Address Configuration Example

/ipv6 address add address=2001:db8:cafe::1/64 interface=bridge1 advertise=yes

The advertise=yes parameter enables router advertisement for prefix delegation.

Viewing IPv6 Addresses

/ipv6 address print

Output:

Flags: D - dynamic, P - pending, G - global, L - link-local
 #   ADDRESS                          INTERFACE      ADV
 0 G 2001:db8:cafe::1/64             bridge1        yes
 1 L fe80::215:5dff:fea0:1/64        ether1         no

DHCP Address Pools

RouterOS can manage address pools for DHCP server assignments or manual allocation.

Creating an Address Pool

/ip pool add name=LAN-Pool ranges=192.168.88.100-192.168.88.200

This creates a pool named LAN-Pool with 101 addresses available for DHCP assignment.

Viewing Pools

/ip pool print

Output:

 # NAME       Ranges
 0 LAN-Pool  192.168.88.100-192.168.88.200

IPv6 Pools

/ipv6 pool add name=LAN-Pool-v6 prefix=2001:db8:cafe::/64 prefix-length=64

Practical Examples

Basic LAN Configuration

Configure a router as a LAN gateway:

/ip address add address=192.168.88.1/24 interface=ether1
/ip address add address=203.0.113.1/30 interface=ether2

This configures:

• ether1: LAN interface with 192.168.88.0/24 network
• ether2: WAN interface with point-to-point link

Secondary Address

Add a secondary network to the same interface:

/ip address add address=10.0.0.1/24 interface=ether1
/ip address add address=172.16.0.1/24 interface=ether1

The interface now responds to both networks.

VLAN Addressing

Assign addresses to VLAN interfaces:

/interface vlan add name=VLAN10 vlan-id=10 interface=bridge1
/ip address add address=192.168.10.1/24 interface=VLAN10

Loopback Address

For router redundancy or OSPF, use loopback addresses:

/interface loopback add name=loopback
/ip address add address=10.255.255.1/32 interface=loopback

IPv6 Prefix Delegation

Configure IPv6 with prefix delegation from an upstream router:

/ipv6 dhcp-client add interface=ether1 pool-name=ipv6-pool add-prefix-length=64 request=prefix
/ipv6 pool add name=ipv6-pool prefix=2001:db8:cafe::/48 prefix-length=64

Troubleshooting

Address Not Appearing

If an address doesn’t appear after configuration:

1. Verify the interface exists and is running:

   /interface print

2. Check for address conflicts:

   /ip address print

3. Verify interface is not disabled:

   /interface ethernet set ether1 disabled=no

Cannot Ping Address

1. Verify the address is assigned:

   /ip address print

2. Check ARP table:

   /ip arp print

3. Verify firewall is not blocking:

   /ip firewall filter print

IPv6 Address Not Working

1. Verify IPv6 is enabled:

   /ipv6 settings print

2. Check for duplicate addresses:

   /ipv6 address print

3. Verify router advertisement settings:

   /ipv6 nd print

Common Configuration Mistakes

Using /32 on a regular interface: Using /32 prevents the router from determining the network, causing routing issues:

# Wrong
/ip address add address=192.168.88.1/32 interface=ether1

# Correct
/ip address add address=192.168.88.1/24 interface=ether1

Network address as host address: The first address in a subnet is the network address and cannot be assigned to hosts:

# Wrong - 192.168.88.0 is the network address
/ip address add address=192.168.88.0/24 interface=ether1

# Correct
/ip address add address=192.168.88.1/24 interface=ether1

Broadcast address as host address: The last address in a subnet is the broadcast address:

# Wrong - 192.168.88.255 is the broadcast address
/ip address add address=192.168.88.255/24 interface=ether1

# Correct - use 192.168.88.254 for last usable
/ip address add address=192.168.88.254/24 interface=ether1

Related Features

• DHCP Server - Automatically assign addresses to clients: /ip dhcp-server
• DHCP Client - Obtain address from upstream: /ip dhcp-client
• IP Settings - Configure system-wide IP parameters: /ip settings
• ARP - Address resolution: /ip arp
• IPv6 ND - Neighbor discovery: /ipv6 nd
• Routing - Route management: /ip route

References

• RFC 791 - Internet Protocol
• RFC 826 - Address Resolution Protocol (ARP)
• RFC 1918 - Address Allocation for Private Internets
• RFC 4193 - Unique Local IPv6 Unicast Addresses
• RFC 4291 - IPv6 Addressing Architecture