Overview

As part of the Fulu consensus node upgrade in Fusaka, Ethereum’s PeerDAS (EIP-7594) will be activated. Ethereum Sepolia’s upgrade is scheduled on October 14th, and Ethereum Mainnet is tentatively targeting December 3rd.

This change optimizes data availability by removing the requirement for all nodes to download all blob data, while still guaranteeing full data availability network-wide. However, this means that node operators for Layer 2 networks, such as Arbitrum One and other Arbitrum L2 chains, will need to make sure they connect to a L1 Ethereum Beacon Chain node that has historical blob data in order for the Nitro node software to function properly.

Failure to do so will result in Arbitrum L2 Nitro nodes failing to fetch blob data properly from Ethereum (Sepolia or Mainnet).

Action Required for Nitro Node Operators

Affected Audience: RPC nodes, Arbitrum One / Nova node operators, Orbit Chain node operators

If you run a Nitro node and use an external L1 Ethereum Beacon Chain RPC URL:

1. We recommend you confirm that your external L1 Beacon Chain RPC provider has configured their L1 Beacon Chain node to subscribe to all subnets before the Ethereum Fusaka hard fork.
   1. For chains that post data and/or sync from Ethereum Sepolia, the Ethereum Sepolia Fusaka hard fork is expected on October 14th, 2025.
   2. For chains that post data and/or sync from Ethereum Mainnet, the Ethereum Mainnet Fusaka hard fork is expected around December 3rd, 2025.
2. If your external L1 Beacon Chain RPC does not subscribe to all subnets, switch to a provider that does before the dates above.

If you run a Nitro node and you also operate your own L1 Ethereum Beacon Chain Node:

1. Add the new flag (see below) to your Beacon Node’s configuration before the Ethereum Fusaka hard fork
   1. For chains that post data and/or sync from Ethereum Sepolia, the Ethereum Sepolia Fusaka hard fork is expected October 14th, 2025.
   2. For chains that post data and/or sync from Ethereum Mainnet, the Ethereum Mainnet Fusaka hard fork is expected around December 3rd, 2025.
2. If you have not added the new flag before the above deadlines:
   1. Please temporarily switch to an external L1 Beacon Chain RPC URL while your local L1 Ethereum beacon chain node syncs up.
      1. Note: ensure that the external L1 Beacon Chain RPC provider you’re using is subscribed to all subnets.
   2. Once your Beacon Chain node is fully synced, you may switch back to your own L1 Beacon Chain RPC URL ****(from an external L1 Beacon Chain RPC URL)

L1 Beacon Chain Node Flags

Prysm CL Client

Prysm nodes have a new beacon node flag --subscribe-all-data-subnets that needs to be added to p2p OPTIONS → 🔗 Prysm Docs: Command-line options.

This is available as of Prysm v6.1.0 (and we recommend always upgrading to stay on the latest stable Prysm releases).