- Although your Yggdrasil configuration will persist, the Yggdrasil package itself **does not** survive an upgrade of the EdgeRouter firmware. You must re-add the repository GPG key and re-install the `vyatta-yggdrasil` package after a system upgrade.
- After upgrading firmware and reinstalling Yggdrasil, use `load` to reload your configuration and then `commit` to make it effective again. Do not run `save` until after you have reloaded your configuration.
At this point, Yggdrasil will start running using default configuration, which includes automatic peer discovery of other Yggdrasil nodes on the same network using multicast.
## Configuration
Once you have generated a configuration file, as above, then you should make configuration changes (like [adding peers](https://github.com/yggdrasil-network/public-peers)) by editing the `/config/yggdrasil.tun0.conf` file.
If you want to allow other IPv6 hosts on your network to communicate through yggdrasil, you can configure an IPv6 masquerade rule. All traffic sent from other hosts on the network through the Yggdrasil interface will be NAT'd.
If you have multiple IPv6 subnets, then they can be configured individually by setting multiple `masquerade from` source ranges. Both private/ULA and public IPv6 subnets are acceptable.
Use this as an example firewall configuration, which will allow outgoing connections but prevent unexpected incoming ones, with the exception of ICMPv6 which will be allowed, e.g. if using `tun0`:
```
configure
set firewall ipv6-name YGG_IN default-action drop
set firewall ipv6-name YGG_LOCAL default-action drop
set firewall ipv6-name YGG_IN rule 10 action accept
set firewall ipv6-name YGG_IN rule 10 state established enable
set firewall ipv6-name YGG_IN rule 10 state related enable
set firewall ipv6-name YGG_IN rule 20 action drop
set firewall ipv6-name YGG_IN rule 20 state invalid enable
set firewall ipv6-name YGG_IN rule 30 action accept
set firewall ipv6-name YGG_IN rule 30 protocol icmpv6
set firewall ipv6-name YGG_LOCAL rule 10 action accept
set firewall ipv6-name YGG_LOCAL rule 10 state established enable
set firewall ipv6-name YGG_LOCAL rule 10 state related enable
set firewall ipv6-name YGG_LOCAL rule 20 action drop
set firewall ipv6-name YGG_LOCAL rule 20 state invalid enable
set firewall ipv6-name YGG_LOCAL rule 30 action accept
set firewall ipv6-name YGG_LOCAL rule 30 protocol icmpv6
set interfaces yggdrasil tun0 firewall in ipv6-name YGG_IN
set interfaces yggdrasil tun0 firewall local ipv6-name YGG_LOCAL