Digi has over a million fiber customers and although the Romanian parent company has transferred new ranges of IP addresses to Spain, it is increasingly dependent on CG-NAT in order to share the few IPv4 in its possession.
1.1 million FTTH lines
Digi continues to grow strongly in Spain, as shown by the results presented by the Romanian parent company updated to June 2023. The operator provides a complete MVNO service to a total of 4.3 million mobile lines. In fiber it is confirmed that it has already more than crossed the milestone of one million customers, with a total of 1,112,000 fiber lines in service.
Extremely aggressive rates, such as 500 Mb fiber for just €15, a price that no rival has dared to challenge, are behind the massive influx of users switching to Digi. Despite the limitations of its mobile phone service, without 5G or VoLTE calls, and the criticism that its fiber has suffered due to the oversubscription of users, the operator continues to be the favorite destination for those who want to reduce spending on telecommunications.
But only 149 thousand IP addresses
This brutal growth puts some services on its network to the test. It is known that Digi uses the CG-NAT system to allow many users to navigate with very few IP addresses. Being a relatively young operator and given that IPv4 addresses have been out of stock for years, it has a much smaller number than other internet providers.
In June 2021, the operator had in its possession 85,504 IPv4 addresses that were shared by 327,000 fiber customers and 2,663,000 mobile customers. Not counting mobile clients, this meant that back then each public IP address was shared between almost 4 fiber clients.
Two years later the situation is much worse. The Romanian parent company has transferred several blocks of addresses to the Spanish subsidiary to be used in our country, so Digi currently has a total of 148,992 IPv4 addresses to serve 1,112,000 fiber lines and 4,300,000 mobile lines.
The greater scarcity of resources means that it is increasingly difficult for Digi to meet the requests of clients who need to get out of CG-NAT by contracting Conexión Plus, necessary to have an IP address that points directly to the router in order to open ports, for example to get open NAT in the console.
Where is the CG-NAT limit?
The CG-NAT translation, or Carrier Grade Network Address Translation, is carried out by a router within the operator's network, modifying the packets that travel between the customer's connection and the Internet. The CG-NAT router has public IP addresses assigned to it, while clients are assigned a private IP address within the 100.64.0.0/10 range. Its job is to translate the client's IP/port on the fly into one of the available public IP/ports, keeping track of this correspondence, so that when data packets come back, it knows which client to send them to.
Each IP can maintain something less than 65 thousand open TCP/IP sessions, as many as there are ports, discounting some reserved ranges. A fiber client with all its devices can maintain an average of 2,000 established TCP/IP sessions, so to avoid problems, the same IP should not be shared among more than 32 users.
Fortunately, the requirements of a mobile client are much lower, since it keeps fewer sessions open and has long idle times, so Digi would still have some margin.