sudo systemctl start mongod (if '/usr/bin/mongod' is not running)
```
### Setting up TUN device (No persistent after rebooting)
---
Create the TUN device. Interface name will be `pgwtun`.
```bash
$ sudo yum -y install iproute
$ sudo ip tuntap add name pgwtun mode tun
$ ip link show
```
Then, to support IPv6-enabled UEs, you must configure your TUN device to support IPv6.
```bash
$ sysctl -n net.ipv6.conf.pgwtun.disable_ipv6
1
$ sudo -w net.ipv6.conf.pgwtun.disable_ipv6=0
$ sysctl -n net.ipv6.conf.pgwtun.disable_ipv6
0
```
**Note:** If your TUN device already supports IPv6, you can skip this steps above.
{: .notice--warning}
You are now ready to set the IP address on TUN device.
```bash
$ sudo ip addr add 45.45.0.1/16 dev pgwtun
$ sudo ip addr add cafe::1/64 dev pgwtun
```
Make sure it is set up properly.
```bash
$ sudo ip link set pgwtun up
$ ip link show
```
**Tip:** The script provided in [$GIT_REPO/support/network/restart.sh](https://github.com/{{ site.github_username }}/nextepc/blob/master/support/network/restart.sh) makes it easy to configure the TUN device as follows:
`$ sudo ./support/network/restart.sh`
{: .notice--info}
### Building NextEPC
---
Install the depedencies for building the source code.
**Tip:** You can also check the result of `make check` with a tool that captures packets. If you are running `wireshark`, select the `loopback` interface and set FILTER to `s1ap || gtpv2 || diameter || gtp`. You can see the virtually created packets. [[testcomplex.pcapng]]({{ site.url }}{{ site.baseurl }}/assets/pcapng/testcomplex.pcapng)