# Recipe to compare VPP API changes between different releases
Use this recipe to generate the list of API changes between versions of VPP:

- Install the baseline version of VPP packages

[https://nexus.fd.io/content/repositories/fd.io$RELEASE.ubuntu.$UBUNTU.main/](https://nexus.fd.io/content/repositories/fd.io$RELEASE.ubuntu.$UBUNTU.main/)

```
export RELEASE=".stable.1801"
export UBUNTU="xenial"
sudo rm /etc/apt/sources.list.d/99fd.io.list
echo "deb [trusted=yes]  ./" | \
    sudo tee -a /etc/apt/sources.list.d/99fd.io.list
sudo apt-get update
sudo apt-get install -y vpp vpp-lib vpp-plugins
```

- Edit /etc/vpp/startup.conf to enable writing the api table to /tmp/api-table. **<release> **

```
api-trace {
## This stanza controls binary API tracing. Unless there is a very strong reason,
## please leave this feature enabled.
  on
## Additional parameters:
##
## To set the number of binary API trace records in the circular buffer, configure nitems
##
## nitems <nnn>
##
## To save the api message table decode tables, configure a filename. Results in /tmp/<filename>
## Very handy for understanding api message changes between versions, identifying missing
## plugins, and so forth.
##
  save-api-table api-table.1801
}
```

- Restart VPP

```
sudo service vpp restart
```

- Verify the API table has been saved

```
ls -l /tmp/api-table.1801
```

- Uninstall the baseline VPP packages

```
sudo apt-get remove -y --purge vpp vpp-lib vpp-plugins
```

- Install the current VPP release

[https://nexus.fd.io/content/repositories/fd.io$RELEASE.ubuntu.$UBUNTU.main/](https://nexus.fd.io/content/repositories/fd.io$RELEASE.ubuntu.$UBUNTU.main/)

```
export RELEASE=".stable.1804"
export UBUNTU="xenial"
sudo rm /etc/apt/sources.list.d/99fd.io.list
echo "deb [trusted=yes]  ./" | \
    sudo tee -a /etc/apt/sources.list.d/99fd.io.list
sudo apt-get update
sudo apt-get install -y vpp vpp-lib vpp-plugins
```

- Dump the API table comparison

```
vppctl show api dump file /tmp/api-table.1801 compare
```

- Uninstall the current VPP packages

```
sudo apt-get remove -y --purge vpp vpp-lib vpp-plugins
```