Activate RA messages

[niousha0]

Hello everyone,
I'm following this tutorial:
https://github.com/cetic/6lbr/wiki/COOJA-Interface
when i use these two commands:

sysctl -w net.ipv6.conf.br0.accept_ra=1
sysctl -w net.ipv6.conf.br0.accept_ra_rt_info_max_plen=64

I face the following error:

sysctl: cannot stat /proc/sys/net/ipv6/conf/br0/accept_ra: No such file or directory
sysctl: cannot stat /proc/sys/net/ipv6/conf/br0/accept_ra_rt_info_max_plen: No such file or directory

please help me on this problem