# Multi-Channel
A Klaytn node can be run with **Multi-channel**.
If a node is executed with multi-channel configuration, 2 ports are set up for communication. On the otherhand, if a node is executed with single channel configuration, 1 port is set up. If 2 multi-channel nodes are trying to connect, a connection is established using 2 ports. Otherwise, they will use 1 port for communication.
A multi-channel node can be enabled through the flag `--multichannel`. If you use [`kend`](https://archive-docs.klaytn.foundation/content/installation-guide/deployment/endpoint-node/installation-guide/startup-the-en), multi-channel is enabled by default due to the statement `MULTICHANNEL=1` in [`kend.conf`](https://archive-docs.klaytn.foundation/content/installation-guide/deployment/endpoint-node/installation-guide/configuration). To disable multi-channel, please replace the statement with `MULTICHANNEL=0`. If you want to run a node with specific ports, flags `port` and `subport` can be used. If you want to specify ports values of a connecting peer, check out [KNI](https://archive-docs.klaytn.foundation/content/klaytn/design/kni).
## Architecture
The picture above shows a connection between two multi-channel nodes. Two ports, mainport (A) and subport (B), transfer different messages.
* **Mainport**(A) is used to transfer messages related to blocks and consensus protocols.
* Block messages include requests and responses of the hash, header, body and receipt of a block.
* Consensus messages include Request, Preprepare, Prepare, Commit and RoundChange. The meaning of the messages can be found in [PBFT](https://archive-docs.klaytn.foundation/content/klaytn/consensus-mechanism#pbft-practical-byzantine-fault-tolerance).
* **Subport**(B) is for transferring transaction messages.
The picture shows a connection between two single channel nodes or between a single channel node and a multi-channel node. In this case, all messages related to blocks, transactions, and consensus protocols are transported via the same port.
## Ports
To set port numbers in KNI, please refer to [the KNI scheme](https://archive-docs.klaytn.foundation/content/klaytn/design/kni).
* Single Channel : A single channel node uses one port (default is 32323).
* Multi-Channel: A multi-channel node uses two ports. The ports can be specified in `port` and `subport`. In Klaytn, the default values of `port` and `subport` are 32323 and 32324, respectively.
* You might not set `subport` when connecting to multi-channel node. In this case, at first, a Klaytn node tries to connect using a single-channel. In handshake process, the actual peer's port numbers are revealed. If the peer is a multi-channel node, the ongoing connection will be canceled and a reconnection will be made with the updated ports.
---
# Agent Instructions: Querying This Documentation
If you need additional information that is not directly available in this page, you can query the documentation dynamically by asking a question.
Perform an HTTP GET request on the current page URL with the `ask` query parameter:
```
GET https://archive-docs.klaytn.foundation/content/klaytn/design/multiport.md?ask=
```
The question should be specific, self-contained, and written in natural language.
The response will contain a direct answer to the question and relevant excerpts and sources from the documentation.
Use this mechanism when the answer is not explicitly present in the current page, you need clarification or additional context, or you want to retrieve related documentation sections.