description: introduction to the devp2p peer-to-peer networking tool
---
[DevP2P](https://github.com/ethereum/devp2p) is a set of network protocols that form the Ethereum peer-to-peer network. The DevP2P specifications define precisely how nodes should find each other and communicate. Geth implements the DevP2P specifications in Go.
The DevP2P stack includes the low-level peer-to-peer protocols that define discovery and secure sessions between nodes such as:
- [Ethereum Node Records](https://github.com/ethereum/devp2p/blob/master/enr.md): A standard format for connectivity information for a node
- [Discovery protocol](https://github.com/ethereum/devp2p/blob/master/discv4.md): Defines how nodes find each other.
- [RLPx protocol](https://github.com/ethereum/devp2p/blob/master/rlpx.md): Defines a TCP based transport system for communication between nodes.
DevP2P also includes the RLPx-based application level protocols including:
- [Ethereum Wire Protocol](https://github.com/ethereum/devp2p/blob/master/caps/eth.md): facilitates exchange of blockchain data between peers
- [Ethereum Snapshot Protocol](https://github.com/ethereum/devp2p/blob/master/caps/snap.md): enables exchange of snapshots between peers
- [Light Ethereum Subprotocol](https://github.com/ethereum/devp2p/blob/master/caps/les.md): protocol used by light clients
To debug and develop these networking components, Geth includes a command line tool called `devp2p`.
This page will outline some of `devp2p`s built-in tools.
Ethereum Node Records can be decoded, verified and displayed to the terminal using `enrdump`. It takes the ENR in its encoded form, which is the base64 encoding of its RLP representation. A decoded human-readable text representation is displayed.
Use `devp2p enrdump <base64>` to verify and display an Ethereum Node Record.
Read more on [Ethereum Node Records](https://ethereum.org/en/developers/docs/networking-layer/network-addresses/#enr) or browse the [specs](https://github.com/ethereum/devp2p/blob/591edbd36eb57280384d07373a818c00bddf3b31/enr.md).
There are several commands for working with JSON node set files. These files are generated by the discovery crawlers and DNS client commands. Node sets also used as the input of the DNS deployer commands.
Run `devp2p nodeset info <nodes.json>` to display statistics of a node set.
Run `devp2p nodeset filter <nodes.json> <filter flags...>` to write a new, filtered node set to standard output. The following filters are supported:
-`-limit <N>` limits the output set to N entries, taking the top N nodes by score
-`-ip <CIDR>` filters nodes by IP subnet
-`-min-age <duration>` filters nodes by 'first seen' time
-`-les-server` filters nodes by LES server support
-`-snap` filters nodes by snap protocol support
For example, given a node set in `nodes.json`, you could create a filtered set containing up to 20 eth mainnet nodes which also support snap sync using this command:
The `devp2p discv5 ...` command family deals with the [Node Discovery v5](https://github.com/ethereum/devp2p/tree/master/discv5/discv5.md) protocol. This protocol is currently under active development.
Run `devp2p discv5 ping <ENR>` to ping a node.
Run `devp2p discv5 resolve <ENR>` to find the most recent node record of a node in the discv5 DHT.
Run `devp2p discv5 listen` to run a Discovery v5 node.
Run `devp2p discv5 crawl <nodes.json path>` to create or update a JSON node set containing discv5 nodes.
The devp2p command also contains interactive test suites for Discovery v4 and Discovery v5. To run these tests a networking environment must be set up with two separate UDP listening addresses are available on the same machine. The two listening addresses must also be routed such
that they are able to reach the node you want to test.
For example, to run the test on the local host when the node under test is also on the local host, assign two IP addresses (or a larger range) to the loopback interface. On macOS, this can be done by executing the following command:
```sh
sudo ifconfig lo0 add 127.0.0.2
```
Either test suite can then be run as follows:
1. Start the node under test first, ensuring that it won't talk to the Internet (i.e. disable bootstrapping). An easy way to prevent unintended connections to the global DHT is listening on `127.0.0.1`.
2. Get the ENR of the node and store it in the `NODE` environment variable.
3. Start the test by running `devp2p discv5 test -listen1 127.0.0.1 -listen2 127.0.0.2 $NODE`.
The Eth66 test suite is also a conformance test suite for the eth 66 protocol version specifically. To run the eth66 protocol test suite, initialize a Geth node as described above and run the following command, replacing `<enode>` with the enode of the Geth node:
This page introduced the DevP2P stack that defines Ethereum's peer-to-peer network and the `devp2p` command line tool that comes bundled with Geth. The `devp2p` tools enables Geth developers to work on the peer-to-peer network.
