sysctl with autocompletion is really great.

> sysctl -n net.
Display all 758 possibilities? (y or n)
> sysctl -n net.ipv
Display all 711 possibilities? (y or n)
> sysctl -n net.ipv4.ip_
net.ipv4.ip_default_ttl           net.ipv4.ip_forward               net.ipv4.ip_local_reserved_ports
net.ipv4.ip_dynaddr               net.ipv4.ip_forward_use_pmtu      net.ipv4.ip_nonlocal_bind        
net.ipv4.ip_early_demux           net.ipv4.ip_local_port_range      net.ipv4.ip_no_pmtu_disc        
> sysctl -n net.ipv4.ip_forward
net.ipv4.ip_forward           net.ipv4.ip_forward_use_pmtu
> sysctl -n net.ipv4.ip_forward
0
> sysctl -w net.ipv4.ip_forward=1
net.ipv4.ip_forward = 1