Example:

# sysctl -a | grep "net.ipv[46].conf.br1" 
net.ipv4.conf.br1.forwarding = 1
net.ipv4.conf.br1.mc_forwarding = 0
net.ipv4.conf.br1.accept_redirects = 1
net.ipv4.conf.br1.secure_redirects = 1
net.ipv4.conf.br1.shared_media = 1
net.ipv4.conf.br1.rp_filter = 0
net.ipv4.conf.br1.send_redirects = 1
net.ipv4.conf.br1.accept_source_route = 1
net.ipv4.conf.br1.proxy_arp = 0
net.ipv4.conf.br1.medium_id = 0
net.ipv4.conf.br1.bootp_relay = 0
net.ipv4.conf.br1.log_martians = 0
net.ipv4.conf.br1.tag = 0
net.ipv4.conf.br1.arp_filter = 0
net.ipv4.conf.br1.arp_announce = 0
net.ipv4.conf.br1.arp_ignore = 0
net.ipv4.conf.br1.arp_accept = 0
net.ipv4.conf.br1.arp_notify = 0
net.ipv4.conf.br1.disable_xfrm = 0
net.ipv4.conf.br1.disable_policy = 0
net.ipv4.conf.br1.force_igmp_version = 0
net.ipv4.conf.br1.promote_secondaries = 1
net.ipv6.conf.br1.forwarding = 1
net.ipv6.conf.br1.hop_limit = 64
net.ipv6.conf.br1.mtu = 1500
net.ipv6.conf.br1.accept_ra = 1
net.ipv6.conf.br1.accept_redirects = 1
net.ipv6.conf.br1.autoconf = 1
net.ipv6.conf.br1.dad_transmits = 1
net.ipv6.conf.br1.router_solicitations = 3
net.ipv6.conf.br1.router_solicitation_interval = 4
net.ipv6.conf.br1.router_solicitation_delay = 1
net.ipv6.conf.br1.force_mld_version = 0
net.ipv6.conf.br1.use_tempaddr = 0
net.ipv6.conf.br1.temp_valid_lft = 604800
net.ipv6.conf.br1.temp_prefered_lft = 86400
net.ipv6.conf.br1.regen_max_retry = 5
net.ipv6.conf.br1.max_desync_factor = 600
net.ipv6.conf.br1.max_addresses = 16
net.ipv6.conf.br1.accept_ra_defrtr = 1
net.ipv6.conf.br1.accept_ra_pinfo = 1
net.ipv6.conf.br1.accept_ra_rtr_pref = 1
net.ipv6.conf.br1.router_probe_interval = 60
net.ipv6.conf.br1.accept_ra_rt_info_max_plen = 0
net.ipv6.conf.br1.proxy_ndp = 0
net.ipv6.conf.br1.accept_source_route = 0
net.ipv6.conf.br1.disable_ipv6 = 0
net.ipv6.conf.br1.accept_dad = 1

# ip addr flush br1

# sysctl -a | grep "net.ipv[46].conf.br1" 
net.ipv4.conf.br1.forwarding = 1
net.ipv4.conf.br1.mc_forwarding = 0
net.ipv4.conf.br1.accept_redirects = 1
net.ipv4.conf.br1.secure_redirects = 1
net.ipv4.conf.br1.shared_media = 1
net.ipv4.conf.br1.rp_filter = 0
net.ipv4.conf.br1.send_redirects = 1
net.ipv4.conf.br1.accept_source_route = 1
net.ipv4.conf.br1.proxy_arp = 0
net.ipv4.conf.br1.medium_id = 0
net.ipv4.conf.br1.bootp_relay = 0
net.ipv4.conf.br1.log_martians = 0
net.ipv4.conf.br1.tag = 0
net.ipv4.conf.br1.arp_filter = 0
net.ipv4.conf.br1.arp_announce = 0
net.ipv4.conf.br1.arp_ignore = 0
net.ipv4.conf.br1.arp_accept = 0
net.ipv4.conf.br1.arp_notify = 0
net.ipv4.conf.br1.disable_xfrm = 0
net.ipv4.conf.br1.disable_policy = 0
net.ipv4.conf.br1.force_igmp_version = 0
net.ipv4.conf.br1.promote_secondaries = 1

There is no br1 interface in the ipv6 tree any more:

# ls /proc/sys/net/ipv6/conf/
all  br0  default  eth0  eth1  lo  tap1.0  tap1.1  tun0

# ls /proc/sys/net/ipv4/conf/
all  br0  br1  default  eth0  eth1  lo  tap1.0  tap1.1  tun0