# Bridge Configuration
In this page, we will describe the steps of connecting a Service Chain to the Main Chain.
## EN Configuration - Enable Main-bridge
You should enable main-bridge by configuring `kend.conf`.
### Update the Configuration File
The `kend.conf` contains the following main-bridge properties.
| Name | Description |
| ---------------------- | --------------------------------------------------------------------------------------------------------- |
| MAIN\_BRIDGE | Enable bridge service as main bridge for service chain. 1 to enable. |
| MAIN\_BRIDGE\_PORT | Bridge listen port. Default: 50505 |
| MAIN\_BRIDGE\_INDEXING | Enable indexing of service chain transaction hash for fast access to the service chain data. 1 to enable. |
To enable main-bridge on EN, you should do like below.
* define `MAIN_BRIDGE`
* enable RPC/WS.
* add `mainbridge` API for RPC like the below example.
```
# Configuration file for the kend
...
# rpc options setting
RPC_ENABLE=1 # if this is set, the following options will be used
RPC_API="klay,mainbridge" # available apis: admin,debug,klay,miner,net,personal,rpc,txpool,web3,mainbridge,subbridge
RPC_PORT=8551
RPC_ADDR="0.0.0.0"
RPC_CORSDOMAIN="*"
RPC_VHOSTS="*"
# ws options setting
WS_ENABLE=1 # if this is set, the following options will be used
WS_API="klay"
WS_ADDR="0.0.0.0"
WS_PORT=8552
WS_ORIGINS="*"
...
# service chain options setting
MAIN_BRIDGE=1
MAIN_BRIDGE_PORT=50505
MAIN_BRIDGE_INDEXING=1
...
```
## Connect SCN to the Main Chain
You need to run an EN of the main chain as a main-bridge. And also you should determine which SCN (Service Chain Consensus Node) as a sub-bridge will connect with the EN.
### Check EN (Main-Bridge) information
#### Open EN Console
There are different ways to attach to the EN process. You can check the usable commands on [ken CLI commands](/content/installation-guide/deployment/endpoint-node/ken-cli-commands.md). This page explains the way to attach to the process via IPC (inter-process communication). The IPC file `klay.ipc` is located in the data directory on the node.
Please execute the following command and check out the result. (If you added `mainbridge` API for RPC, you can check the bridge API like below. If there is no `mainbridge` API, you should check [EN Configuration - Enable Main-bridge](#en-configuration-enable-main-bridge) again. )
```bash
$ ken attach ~/kend_home/klay.ipc
Welcome to the Klaytn JavaScript console!
instance: Klaytn/vX.X.X/XXXX-XXXX/goX.X.X
at block: 11573551 (Wed, 13 Feb 2019 07:12:52 UTC)
datadir: ~/kend_home
modules: admin:1.0 mainbridge:1.0 debug:1.0 istanbul:1.0 klay:1.0 miner:1.0 net:1.0 personal:1.0 rpc:1.0 txpool:1.0
>
```
#### Get the EN's KNI
After attaching to the process via IPC, you can check the EN's main-bridge KNI like below. You can refer to [Service Chain API](/content/dapp/json-rpc/servicechain/subbridge.md).
```javascript
> mainbridge.nodeInfo
{
kni: "kni://08b99d2297e0a27ddeb33f3a81b59ea1c065b9adbaff9fefab0d16f65b1a8db22939a104c24447e9aca521c158922ca912476b544baf48995a382d88886e0a37@[::]:50505?discport=0",
id: "08b99d2297e0a27ddeb33f3a81b59ea1c065b9adbaff9fefab0d16f65b1a8db22939a104c24447e9aca521c158922ca912476b544baf48995a382d88886e0a37",
ip: "::",
listenAddr: "[::]:50505",
name: "-2",
ports: {
discovery: 0,
listener: 50505
},
protocols: {
servicechain: {
config: {
chainId: 2018,
deriveShaImpl: 0,
isBFT: true,
istanbul: {...},
unitPrice: 0
},
difficulty: 87860,
genesis: "0x711ce9865492659977abb2758d29f68c2b0c82862d9376f25953579f64f95b58",
head: "0x0d4b130731f1e7560e4531ac73d55ac8c6daccb178abd86af0d96b7aafded7c5",
network: 1
}
}
}
```
You should take note of the main-bridge `kni`.
### Connect to the Main Chain
#### Open SCN Console
Attach to the SCN process like below. You should have enabled `subbridge` API for RPC, you can find the subbridge module in the output. If there is no `subbridge` API, you should check [Configuration of the SCN](/content/installation-guide/deployment/service-chain/references/scn/configuration.md#configuration-of-the-scn) again.
```bash
$ kscn attach ~/kscnd_home/klay.ipc
Welcome to the Klaytn JavaScript console!
instance: Klaytn/vX.X.X/XXXX-XXXX/goX.X.X
datadir: ~/kscnd_home
modules: admin:1.0 subbridge:1.0 debug:1.0 governance:1.0 istanbul:1.0 klay:1.0 miner:1.0 net:1.0 personal:1.0 rpc:1.0 servicechain:1.0 txpool:1.0
>
```
#### Connect SCN with EN
You can add the EN peer on SCN via IPC like below. The kni is EN's KNI which you noted previously.
```javascript
> subbridge.addPeer("kni://08b99d2297e0a27ddeb33f3a81b59ea1c065b9adbaff9fefab0d16f65b1a8db22939a104c24447e9aca521c158922ca912476b544baf48995a382d88886e0a37@[::]:50505?discport=0")
true
```
And then you can check the connected peers like below.
```javascript
> subbridge.peers
[{
caps: ["servicechain/1"],
id: "08b99d2297e0a27ddeb33f3a81b59ea1c065b9adbaff9fefab0d16f65b1a8db22939a104c24447e9aca521c158922ca912476b544baf48995a382d88886e0a37",
name: "-1",
networks: [{
inbound: false,
localAddress: "[::1]:56834",
remoteAddress: "[::1]:50505",
static: true,
trusted: false
}],
protocols: {
servicechain: {
head: "0x47be444be87daaee2989998559049ee8a859540807824dd1db4a80ea6cb42293",
version: 1
}
}
}]
```
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