IP Pools in RouterOS: A Complete Guide

IP Pools in RouterOS: A Complete Guide

RouterOS Version: 7.x+ Difficulty: Beginner Estimated Time: 15 minutes

Overview

IP Pools define ranges of IP addresses for dynamic allocation by RouterOS services. They act as address reservoirs—services draw addresses when clients connect and return them when clients disconnect.

Services that use IP pools:

• DHCP Server - Dynamic IP assignment for network clients
• PPP (PPPoE, PPTP, L2TP, SSTP) - VPN client addressing
• Hotspot - Captive portal client addressing
• User Manager - RADIUS-based address assignment

Key features:

• Multiple non-contiguous ranges in a single pool
• Pool chaining via next-pool for overflow handling
• Consistent address assignment for returning clients
• IPv6 prefix pools for DHCPv6 prefix delegation

Menu Reference

Menu	Purpose
/ip pool	IPv4 address pools
/ip pool used	Currently assigned addresses
/ipv6 pool	IPv6 prefix pools
/ipv6 pool used	Currently assigned prefixes

IPv4 Pool Properties

Property	Type	Default	Description
name	string	-	Unique pool identifier (required)
ranges	IP range list	-	Address ranges: from-to,from-to,... (required)
next-pool	string	none	Fallback pool when current exhausted
comment	string	-	Descriptive comment

IPv6 Pool Properties

Property	Type	Default	Description
name	string	-	Pool identifier (required)
prefix	IPv6 prefix	-	Base prefix to allocate from (required)
prefix-length	integer	-	Size of allocations (required)
comment	string	-	Descriptive comment

Configuration Examples

Example 1: Basic DHCP Pool

Create a pool for DHCP server:

# Create pool (exclude router IP .1)
/ip pool add name=dhcp-pool ranges=192.168.88.10-192.168.88.254

# Verify
/ip pool print

Important: Never include the router’s own IP in the pool range!

Example 2: Multiple Non-Contiguous Ranges

Reserve some addresses while using others:

# IPs .1-.9 reserved for servers, .100-.149 for printers
/ip pool add name=office-pool ranges=10.0.0.10-10.0.0.99,10.0.0.150-10.0.0.254

Example 3: Pool Chaining (Overflow)

Automatically use secondary pool when primary exhausts:

# Primary pool
/ip pool add name=pool-primary ranges=192.168.1.10-192.168.1.100

# Overflow pool
/ip pool add name=pool-overflow ranges=192.168.1.150-192.168.1.200

# Chain them
/ip pool set pool-primary next-pool=pool-overflow

When pool-primary is full, new requests automatically get addresses from pool-overflow.

Example 4: PPP/VPN Client Pool

For PPPoE, L2TP, or other PPP-based VPNs:

# Create pool
/ip pool add name=vpn-pool ranges=10.10.10.2-10.10.10.254

# Create PPP profile using pool
/ppp profile add name=vpn-profile local-address=10.10.10.1 remote-address=vpn-pool

Note: PPP assigns addresses from the END of the range first (working downward).

Example 5: Hotspot Pool

For captive portal clients:

# Create pool
/ip pool add name=hotspot-pool ranges=10.5.50.2-10.5.50.254

# Use in hotspot
/ip hotspot add name=hs1 interface=wlan1 address-pool=hotspot-pool

Example 6: IPv6 Prefix Pool

For DHCPv6 prefix delegation:

# Allocate /64 prefixes from a /56 block
/ipv6 pool add name=pd-pool prefix=2001:db8:1000::/56 prefix-length=64

# Use with DHCPv6 server
/ipv6 dhcp-server add name=dhcp6 interface=bridge address-pool=pd-pool

This creates 256 available /64 prefixes for clients.

Example 7: DHCP Server with Pool

Complete DHCP setup:

# Step 1: Create pool
/ip pool add name=lan-pool ranges=192.168.88.10-192.168.88.254

# Step 2: Configure network options
/ip dhcp-server network add address=192.168.88.0/24 gateway=192.168.88.1 \
    dns-server=192.168.88.1

# Step 3: Create DHCP server
/ip dhcp-server add name=dhcp-lan interface=bridge address-pool=lan-pool disabled=no

# Step 4: Verify
/ip dhcp-server print

Example 8: Monitor Pool Usage

# View all pools with usage
/ip pool print

# View addresses currently in use
/ip pool used print

# Count addresses in use
/ip pool used print count-only

# Find specific client by MAC
/ip pool used print where info~"00:11:22:33:44:55"

How Address Assignment Works

Consistent Assignment

RouterOS tries to give the same IP to returning clients based on:

Service	Client Identifier
DHCP	MAC address
PPP	Username
Hotspot	MAC address

This enables predictable addressing without static reservations.

Assignment Order

Service	Order
DHCP	First available (ascending)
PPP	Last available (descending)

PPP’s reverse order is by design and differs from other vendors.

Pool Exhaustion with next-pool

Client Request
      │
      ▼
┌─────────────────┐
│  Primary Pool   │───▶ Address available? ─── Yes ──▶ Assign
│  (pool-primary) │                │
└─────────────────┘                │ No
                                   ▼
                    ┌─────────────────┐
                    │  Overflow Pool  │───▶ Assign from here
                    │  (pool-overflow)│
                    └─────────────────┘

Common Problems and Solutions

Problem 1: Router’s IP Assigned to Client

Symptom: Network failure; router loses connectivity.

Cause: Pool range includes router’s interface IP.

Solution:

# Wrong: includes .1
/ip pool add name=bad-pool ranges=192.168.88.1-192.168.88.254

# Correct: excludes .1
/ip pool add name=good-pool ranges=192.168.88.10-192.168.88.254

Problem 2: DHCP Says “Pool Empty” But Addresses Available

Causes:

• Client-ID variations causing duplicate entries
• Infrastructure issues (faulty hardware causing reconnections)

Solutions:

# Limit one IP per MAC
/ip dhcp-server set [find] client-mac-limit=1

# Check for duplicates
/ip pool used print

# Shorten lease time to recycle faster
/ip dhcp-server set [find] lease-time=1h

Problem 3: Client Gets /32 Netmask and No Gateway

Cause: Pool addresses don’t match any DHCP network entry.

Solution:

# Ensure network covers pool range
/ip dhcp-server network add address=192.168.88.0/24 gateway=192.168.88.1

# Verify pool is within network
/ip pool print
# Pool range must fall within 192.168.88.0/24

Problem 4: next-pool Not Working

Causes:

• Typo in pool name
• Pools in different subnets (for DHCP)

Solution:

# Verify pool names match exactly (case-sensitive)
/ip pool print

# For DHCP, all chained pools must be in same subnet

Problem 5: Hotspot Pool Not Releasing Addresses

Cause: No idle timeout configured.

Solution:

# Configure idle timeout
/ip hotspot set [find] idle-timeout=5m

Problem 6: PPP User Has Multiple IPs

Cause: Stale sessions not terminating cleanly.

Solution:

# Check actual active sessions
/ppp active print

# Configure session timeout in profile
/ppp profile set [find] session-timeout=1d

Problem 7: IPv6 Pool Exhausted After One Assignment

Cause: prefix-length not set correctly.

Solution:

# Wrong: no prefix-length means one allocation
# Correct: set prefix-length to desired size
/ipv6 pool set [find] prefix-length=64

Pool Capacity Planning

Network Size	Pool Range	Usable Addresses
/24	.10-.254	~244
/23	2 × /24	~509
/22	4 × /24	~1021
/20	16 × /24	~4093

Formula: Usable = 2^(32-prefix) - 3 (network, broadcast, gateway)

Tip: Leave headroom for growth. A pool at 80%+ capacity may need expansion.

Verification Commands

# List all pools
/ip pool print

# Check pool utilization
/ip pool print
# Compare "Total" vs addresses in use

# View active assignments
/ip pool used print

# View specific pool usage
/ip pool used print where pool=dhcp-pool

# Count addresses in use
/ip pool used print count-only

# Find client by MAC
/ip pool used print where info~"AA:BB:CC"

# Check IPv6 pools
/ipv6 pool print
/ipv6 pool used print

Integration with Other Features

DHCP Server

/ip dhcp-server add address-pool=my-pool ...

PPP Profile

/ppp profile add remote-address=my-pool ...

Hotspot

/ip hotspot add address-pool=my-pool ...

RADIUS (Framed-Pool attribute)

RADIUS can specify pool per-user using Framed-Pool attribute.

Related Topics

Prerequisites

• IP Address Configuration - interface addressing fundamentals

Primary Use Cases

• DHCP Server - primary pool consumer for automatic IP distribution
• DHCP Relay - centralized DHCP requires pools for each relay subnet

Related Services

• PPP Profile (/ppp profile) - uses pools for VPN clients
• Hotspot Setup - uses pools for captive portal
• DHCPv6 Server - uses IPv6 pools

Edge Cases and Limitations

• Pool names are case-sensitive - Pool1 ≠ pool1
• Ranges cannot overlap with other pools or static addresses
• Deleting pool with active assignments orphans those addresses
• DHCP pools must match network entries - otherwise clients get /32 netmask
• PPP assigns from end first - by design, not a bug
• next-pool must be same subnet for DHCP (different subnets won’t route)
• IPv6 prefix-length must be ≥ pool prefix - can’t allocate larger than source

Summary

IP Pools are address reservoirs for RouterOS services:

1. Create pool with appropriate ranges (exclude router IPs)
2. Configure service to use pool by name
3. Monitor usage with /ip pool used print
4. Chain pools with next-pool for overflow handling

Key points:

• Never include router’s own IP in pool range
• DHCP needs matching /ip dhcp-server network entry
• PPP assigns from end of range (descending)
• Pool names are case-sensitive
• Use next-pool for automatic overflow to secondary pool