https://forums.gentoo.org/viewtopic-p-8033710.html#8033710
Thank you, krinn
# grep -n "(ip l2tp show session" /lib/netifrc/net/l2tp.sh | cut -d ":" -f1 | xargs -I {} sed -i '{}s/eval/ip l2tp show session 2\>\/dev\/null \&\& eval/g' /lib/netifrc/net/l2tp.sh