Network administrators are faced with a great challenge while selecting the Public IP address space to be used on newly provisioned Internet link. The IP address space has to be one of the following –
(1) Provider Aggregatable (PA)
(2) Provider Independent (PI)
PA (Provider Aggregatable) address assignments made by a Provider and come from a large block allocated to a Provider by RIPE.
PI (Provider Independent) addresses are individually assigned, do not have a specific provider relation and are always routed independently on the global Internet by themselves as a separate block.
While designing, an experienced mind can be life saver because the IP address space selection will depend on many factors like –
- Internet failover scenarios (Multi homing)
- Web facing and Internet browsing application requirements
- Internet Link Failover approach.
PI vs PA : Comparison Table
Below table will help give insight how both differ:
|PA (PROVIDER AGGREGATABLE)
|PI (PROVIDER INDEPENDENT)
|IP pool announcement
|Only can be advertised by Service provider owning the Address Pool
|Can be advertised by customer through any service provider through BGP
|BGP Based routing
|BGP may not be required for providing redundant connectivity
|BGP is one of majorly used routing option for providing redundancy
|Address Block Size
|Can be longer IP block of /25 or /26
|At least /24 IP Block size
|IP address Assignment
|PA addresses are assigned from an LIR’s allocation and are registered in the RIPE Database by the LIR
|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
|Easier to implement and control. NAT configuration can do the trick.
|Complex BGP based routing required for traffic control and providing redundancy
|Route aggregation and CIDR at provider end
|Possible and this provides flexibility to service provider.
|Needs to be changed when moving from one service provider to another
|Don’t need to be changed when moving from one service provider to another
|Cost cheaper than PI address block.
|Costlier than PA address block.