document rootless container with own outgoing IP

admin-guide/container.md

@@ -55,3 +55,14 @@ curl "https://sysdb.psi.ch/subid/v1/config?user=$USER1&user=$USER2&user=$USER3"
 **Future Work**:
 - Puppet integration
 - automatic refresh on login
+
+
+### Rootless Podman Container with own External IP
+
+1. add additional IP address to your network interface
+2. make the container use that IP address:
+```
+podman run -it --rm --network=pasta:--ipv4-only,--address,192.168.254.254,--outbound,192.168.254.254 rhel9:latest  /bin/bash
+```
+3. disable DNS caching with `networking::enable_dns_caching: false` because with the outbound IP communication does not work over the `lo` interface which is used by `systemd-resolved` (maybe some hiding NAT rule would help).
+--outbound,129.129.187.254