PI vs PA Resources: Key Differences

When planning your organization's IP address strategy, one of the most fundamental decisions you'll face is choosing between Provider Independent (PI) and Provider Aggregatable (PA) address space. This choice impacts your network architecture, operational flexibility, costs, and long-term infrastructure planning. This article provides a comprehensive comparison to help you make an informed decision.

Overview: PI vs PA at a Glance

Provider Independent (PI) addresses are assigned directly by Regional Internet Registries (RIRs) like RIPE NCC and remain with your organization regardless of your Internet Service Provider.

Provider Aggregatable (PA) addresses are allocated to Local Internet Registries (LIRs) - typically ISPs - who then sub-allocate or assign them to their customers.

The choice between PI and PA fundamentally comes down to independence vs. efficiency: PI addresses offer maximum flexibility and portability at the cost of routing complexity, while PA addresses optimize Internet routing efficiency but create provider dependency.

For a comprehensive overview of PI resources, see our guide to Understanding Provider Independent (PI) Resources.

Source and Assignment Authority

The first major difference lies in who assigns the address space and from where it originates.

Provider Aggregatable (PA) Addresses

Source: PA addresses come from allocations given to Local Internet Registries (LIRs).

According to RIPE policy: "LIRs are allocated Provider Aggregatable (PA) address space. They sub-allocate and assign this to downstream networks."

Assignment process:

1. RIPE NCC allocates large blocks to LIRs (typically ISPs)
2. LIRs maintain these allocations in their pools
3. LIRs assign portions to their customers based on demonstrated need
4. LIRs register assignments in the RIPE Database

Registration: "PA addresses are assigned from an LIR's allocation and are registered in the RIPE Database by the LIR."

Provider Independent (PI) Addresses

Source: PI addresses are assigned separately, not from any LIR's allocation pool.

From RIPE documentation: "PI address space is assigned separately and not from an LIR's PA allocation. All PI assignments are registered in the RIPE Database by the RIPE NCC at the time they are assigned."

Assignment process:

1. End user requests PI assignment (directly or through sponsoring LIR)
2. RIPE NCC evaluates request against PI assignment policies
3. Upon approval, RIPE NCC assigns space from dedicated PI pools
4. RIPE NCC registers the assignment in the RIPE Database

The key distinction: PA space flows through the LIR hierarchy, while PI space comes directly from the RIR to the end user.

Portability and Provider Independence

This is perhaps the most critical differentiator for many organizations.

PA Address Portability

Non-portable: PA addresses are fundamentally tied to your LIR/ISP relationship.

RIPE policy mandates that customers receive clear warnings about PA space: "Assignment of this IP space is valid as long as the criteria for the original assignment are met and only for the duration of the service agreement between yourself and us. We have the right to reassign the address space to another user upon termination of this agreement or an agreed period thereafter."

Implications of changing ISPs:

• You must return PA addresses when you terminate service
• Your network requires complete renumbering
• All DNS records need updating
• Firewall rules, ACLs, and security policies require revision
• Certificates and services tied to IP addresses must be reconfigured
• Downtime during the transition period

Use case fit: PA addresses work well when you:

• Have a stable, long-term relationship with a single ISP
• Don't require multi-homing capabilities
• Can tolerate renumbering if you change providers
• Want to minimize costs and administrative overhead

PI Address Portability

Fully portable: PI addresses remain with your organization indefinitely.

From RIPE documentation: "PI address space remains assigned to its user as long as the criteria for the original assignment are met independently of the use of a particular provider's services."

Provider independence benefits:

• Switch ISPs without renumbering your network
• Maintain all services, configurations, and DNS during provider changes
• No downtime related to address changes
• Freedom to negotiate with multiple providers
• Leverage competition between ISPs for better rates

Multi-homing capability: PI addresses enable connecting to multiple ISPs simultaneously for:

• Redundancy and failover protection
• Load distribution across links
• Traffic engineering and path optimization
• Increased resilience

Use case fit: PI addresses are essential when you:

• Require multi-homing for business continuity
• Need stable addressing for critical infrastructure
• Want freedom to change providers without disruption
• Operate data centers or hosting services
• Run services requiring consistent IP addressing

Routing and Internet Reachability

The way PA and PI addresses affect Internet routing differs significantly.

PA Address Routing Advantages

Aggregation efficiency: The fundamental advantage of PA addresses is aggregation.

RIPE states: "The advantage of PA addresses is that the routing information for many customers can be aggregated once it leaves the provider's routing domain."

How aggregation works:

• An ISP receives a /19 allocation (8,192 addresses)
• They assign /24 blocks to 32 different customers
• The ISP announces only the /19 to the global Internet
• One routing table entry covers all 32 customer assignments

Global routing impact: This aggregation dramatically reduces global routing table size. Without PA aggregation, the Internet routing infrastructure would face severe scalability challenges.

Universal routing acceptance: PA addresses from established ISPs are universally routed. Since they're part of aggregated blocks, filtering is unlikely.

PI Address Routing Considerations

Lack of aggregation: PI assignments typically require individual routing table entries.

RIPE notes: "PI assignments are typically small in scope and cannot be consolidated into larger blocks, unlike PA space."

Routing table impact: Each PI assignment adds to the global routing table:

• More memory required in Internet routers
• Longer BGP convergence times
• Increased routing protocol overhead
• Scalability concerns for Internet infrastructure

Routing acceptance challenges: Not all networks guarantee to route PI addresses.

From RIPE documentation: "The disadvantage of this is that networks operators throughout the Internet may choose not to route them."

Practical considerations:

• Most major networks route properly-registered PI space
• Smaller PI blocks may face more filtering
• Implementation of ROAs via RPKI improves acceptance
• Working with well-connected ISPs helps
• Proper IRR registration is essential

Important note from RIPE policy: "Assignment of address space does NOT imply that this address space will be ROUTABLE ON ANY PART OF THE INTERNET. It is expected that users will have to pay a premium for actual routing of PI addresses as opposed to PA addresses."

Ownership and Control

The relationship between the address holder and the address space differs fundamentally.

PA Address Control

ISP ownership: The LIR holds the allocation; you receive an assignment from that allocation.

Limited control:

• No direct relationship with RIPE NCC for the addresses
• ISP controls RIPE Database entries
• Reverse DNS typically managed by ISP
• Transfer rights remain with the LIR, not the assignment holder

Dependency relationship: Your right to use PA addresses derives from your service contract with the ISP.

PI Address Control

Direct rights: You hold the assignment directly (though RIPE NCC owns the addresses).

Greater control:

• Direct or sponsored relationship with RIPE NCC
• Control over RIPE Database objects (through maintainer)
• Manage reverse DNS independently
• Can transfer assignment to other organizations (for IPv4 PI)

Contractual relationship: "End Users of provider independent resources are responsible for maintaining a contractual link to the RIPE NCC either through a sponsoring LIR or else directly to the RIPE NCC for the purposes of managing these resources."

Cost Comparison

Financial considerations often play a significant role in the PI vs PA decision.

PA Address Costs

Included in service: PA addresses are typically provided as part of your ISP service contract.

No direct fees: You don't pay RIPE NCC directly for PA addresses.

ISP costs: Address costs are incorporated into:

• Monthly service fees
• Setup charges
• Port costs
• Bandwidth pricing

Lower barrier to entry: No upfront costs or separate contracts for address space.

PI Address Costs

Direct fees to RIPE NCC: PI holders pay annual maintenance fees.

2025 fee structure:

• IPv4 PI assignment: €75 per year
• IPv6 PI assignment: €75 per year
• ASN (often needed with PI): €50 per year

Sponsoring LIR fees: If using a sponsoring LIR (most common):

• Initial setup fees: €200-500 typically
• Annual service fees: €100-300 typically
• Application support fees: Variable

Total annual cost: Expect €200-500 per year for PI resources including all fees.

Additional costs:

• BGP-capable router hardware
• Technical staff expertise
• Potential premium ISP fees for PI routing

Cost-benefit analysis: While PI resources have direct costs, they can provide savings through:

• Elimination of renumbering costs
• ISP negotiating flexibility
• Reduced downtime from provider changes
• Multi-homing without NAT complexity

Availability: IPv4 vs IPv6

The scarcity of IPv4 addresses has created a stark difference in availability.

IPv4 Availability

PA addresses: Available through ISPs from their existing allocations or last /22 holdings. Most established ISPs can provide small IPv4 PA assignments to customers.

PI addresses: No longer available as new assignments from RIPE NCC.

RIPE states clearly: "As the RIPE NCC has run out of IPv4 addresses, no new IPv4 PI address space can be assigned."

IPv4 PI options:

• Transfer market: Purchase existing PI assignments from current holders
• Leasing: Rent IPv4 space (typically PA from brokers)
• IPv6 deployment: Transition to IPv6 as primary addressing

IPv6 Availability

Both PA and IPv6 PI readily available: The vast IPv6 address space means both options remain accessible.

PA addresses: LIRs receive minimum /32 allocations and can assign to customers as needed.

PI addresses: Standard /48 assignments available through normal application process.

Technical Requirements

The technical complexity and expertise required differ significantly.

PA Address Technical Requirements

Minimal complexity:

• Standard customer edge router
• Static routing or basic dynamic routing
• ISP handles all BGP and Internet routing
• Simple configuration and management

ISP support: Your ISP manages:

• BGP routing and announcements
• Route filtering and policies
• Peering relationships
• Traffic engineering

Lower expertise needs: Basic networking knowledge sufficient for most PA deployments.

PI Address Technical Requirements

Higher complexity:

• BGP-capable edge routers (enterprise-grade)
• Autonomous System Number (ASN)
• BGP routing protocol expertise
• Route policy configuration
• RPKI implementation

Independent management: You or your team handles:

• BGP configuration with multiple ISPs
• Route announcements and filtering
• Traffic engineering policies
• Monitoring and troubleshooting
• RIPE Database maintenance

Expertise requirements:

• BGP protocol understanding
• Internet routing knowledge
• RIPE policy familiarity
• Network security best practices

Alternative: Many organizations using PI space engage managed service providers or networking consultants to handle technical complexity.

Regulatory and Policy Compliance

Both PA and PI resources come with obligations, but the relationship differs.

PA Address Compliance

ISP responsibility: The LIR maintains primary responsibility for policy compliance.

End user obligations:

• Use addresses as specified in service agreement
• Don't redistribute or sublease addresses
• Provide accurate information to ISP

RIPE oversight: "The LIR is contractually responsible for ensuring the address space allocated to it is used in accordance with the RIPE community's policies."

PI Address Compliance

Direct obligation: PI holders bear direct responsibility for policy compliance.

Requirements from RIPE policy:

• Maintain contractual relationship with RIPE NCC
• Use resources only for own infrastructure (no sub-assignment)
• Keep RIPE Database information current
• Respond to RIPE NCC inquiries and audits
• Pay annual fees on time

Resource types covered: "Provider independent resources include autonomous system numbers, provider independent IPv4 address assignments, anycast assignments, provider independent IXP IPv6 address assignments, and all future provider independent resource assignments to End Users."

Audit exposure: PI holders may face RIPE NCC audits to verify compliance.

Decision Framework: Which is Right for You?

Choose PA Addresses When:

• Single-homed network: Connection to one ISP is sufficient
• Cost sensitivity: Minimizing direct costs is priority
• Simplicity preference: Want ISP to handle routing complexity
• Stable provider relationship: Long-term ISP commitment acceptable
• Renumbering tolerance: Can accommodate provider changes with network renumbering
• Small-scale operation: Limited infrastructure with basic needs

Choose PI Addresses When:

• Multi-homing required: Need redundant ISP connections
• Provider independence critical: Must avoid vendor lock-in
• Stable addressing essential: Infrastructure depends on consistent IPs
• Frequent provider changes: Business model involves ISP flexibility
• Technical capability available: Staff expertise or consultant support for BGP
• Long-term investment: Building infrastructure for years ahead
• Data center operations: Hosting services requiring stable addressing
• Enterprise criticality: Internet presence is mission-critical

Hybrid Approaches

Some organizations use both PA and PI addressing:

PA for general use: Standard office networks, non-critical services PI for critical infrastructure: Public-facing services, data centers, key applications

This approach balances cost efficiency with strategic flexibility.

Migration Considerations

Organizations sometimes need to transition between PA and PI (or vice versa).

PA to PI Migration

Reasons to migrate:

• Growing need for multi-homing
• Desire for provider independence
• Expanding to data center operations
• Increasing infrastructure criticality

Migration steps:

1. Obtain PI assignment (IPv6 PI or transfer for IPv4 PI)
2. Configure parallel infrastructure with PI addresses
3. Update DNS records with parallel entries
4. Gradually migrate services to PI addressing
5. Decommission PA addresses after full migration
6. Return PA space to ISP

Challenges: Complete renumbering required, but one-time cost for long-term flexibility.

PI to PA Migration

Reasons to migrate (rare):

• Reducing operational complexity
• Eliminating PI maintenance costs
• Simplifying technical requirements

Migration steps:

1. Arrange PA addresses with ISP
2. Plan service migration timeline
3. Update configurations, DNS, and dependencies
4. Return PI assignment to RIPE NCC (or transfer to another organization)
5. Terminate PI contractual relationship

Real-World Use Cases

Case Study: PA Addresses - Regional Office

Scenario: A 50-person regional office of an international company.

Requirements:

• Internet access for staff
• VPN connectivity to headquarters
• Standard office applications
• Single ISP connection

Decision: PA addresses

• Cost-effective solution
• ISP handles all routing
• No multi-homing needs
• Renumbering acceptable if changing ISPs

Case Study: PI Addresses - Hosting Provider

Scenario: A hosting company offering dedicated servers and colocation.

Requirements:

• Stable IP addressing for customer servers
• Multi-homing for redundancy
• Provider independence
• Professional network operations

Decision: PI addresses (IPv4 and IPv6)

• Customer services require stable IPs
• Cannot renumber customer infrastructure
• Multi-homing essential for uptime SLA
• Technical expertise available in-house

Case Study: Hybrid Approach - Enterprise

Scenario: Large enterprise with headquarters, regional offices, and data center.

Requirements:

• Critical services in data center
• Standard connectivity for offices
• Cost optimization
• Operational efficiency

Decision: Hybrid approach

• PI addresses for data center (multi-homed, critical)
• PA addresses for office locations (cost-effective, manageable)
• Best of both worlds

Common Misconceptions

"PI addresses are always better"

Reality: PI addresses provide specific benefits but come with costs, complexity, and routing considerations. PA addresses are often the right choice for many organizations.

"PA addresses mean you don't own your IPs"

Reality: Neither PA nor PI holders "own" the addresses. RIPE NCC (and ultimately IANA) owns the address space. Both PA and PI provide usage rights under specific conditions.

"PI addresses guarantee global routing"

Reality: RIPE explicitly states that address assignment doesn't guarantee routing. While most networks route properly-registered PI space, it's not guaranteed.

"PA addresses prevent multi-homing"

Reality: You can multi-home with PA addresses using techniques like NAT or BGP with provider ASNs, though PI space makes multi-homing significantly simpler and more effective.

Summary: Key Differences at a Glance

Aspect	PA Addresses	PI Addresses
Source	From ISP/LIR allocation	Direct from RIR
Portability	Non-portable, ISP-tied	Fully portable
Provider Independence	Dependent on ISP	Fully independent
Routing Efficiency	Aggregatable, efficient	Individual entries
Global Routing	Universal acceptance	Possible filtering
Direct Costs	Included in ISP service	€200-500/year typical
Technical Complexity	Low	Moderate to high
Control Level	Limited	High
Multi-homing	Difficult	Natural fit
IPv4 Availability	Through ISPs	Transfer market only
IPv6 Availability	Readily available	Readily available
Best For	Single-homed networks	Multi-homed, critical infrastructure

Frequently Asked Questions

Can I convert my PA addresses to PI addresses?

No, you cannot convert PA to PI. They're fundamentally different types of assignments. To move from PA to PI, you must obtain a PI assignment and renumber your network.

Do I need an ASN to use PI addresses?

Not technically required, but highly recommended. Most benefits of PI addressing come from using your own ASN for BGP routing. Static routing PI addresses through a single ISP negates most PI advantages.

Which is more expensive long-term?

It depends on your situation. PI has direct costs (fees) and technical costs (expertise, equipment). PA costs are built into ISP fees. For organizations changing ISPs occasionally, renumbering costs with PA can exceed PI maintenance costs.

Can I use PI addresses with just one ISP?

Yes, but you lose most PI benefits. Single-homed PI addresses provide stable addressing and provider switching flexibility but don't enable multi-homing benefits.

What if my ISP won't route my PI addresses?

While rare with established ISPs, if one provider won't route your PI space, you can switch to another ISP. This is actually a demonstration of PI's value - provider independence. Ensure proper registration in IRR and implement RPKI to maximize acceptance.

Can I later switch from PA to PI or vice versa?

Yes, but it requires renumbering your network. Organizations sometimes start with PA and migrate to PI as they grow and require multi-homing, or occasionally move from PI to PA to reduce complexity.

Next Steps

Understanding the differences between PI and PA addresses helps you make informed decisions for your network infrastructure.

If you're considering PI resources:

• Review our comprehensive guide: Understanding Provider Independent (PI) Resources
• Learn about eligibility: IPv4 PI Eligibility Requirements
• Understand sizes: IPv6 PI Allocation Sizes Explained
• Explore the process: RIPE PI Resource Application Process

Need guidance on the right choice for your organization? Contact Via-Registry for a consultation. Our team can assess your requirements and recommend the optimal addressing strategy.

Ready to obtain PI resources? Via-Registry provides comprehensive support for PI applications and ongoing management:

• IPv4 PI Resources Service
• IPv6 PI Resources Service

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This article is part of our comprehensive resource library on IP addressing and Internet resources. For personalized guidance on address space planning, contact our team or explore our service offerings.