VLAN results in two interfaces with the same link-local IPv6 address, is that ok?

[hgl]

My br-lan uses port eth0, and my br-guest uses port eth0.2, this results in them having the same mac address and thus the same link-local IPv6 address, I wonder if this can cause problems down the road or I should manually specify a different mac for one of them?

[eduperez]

Something smells wrong here... can you post your network and wireless config files, please?

[hgl]

Thanks for the quick reply.

This is the minimal config to reproduce (It's a x86 pc with no wireless), with master openwrt:

/etc/config/network

...

config device
	option name 'br-lan'
	option type 'bridge'
	list ports 'eth0'

config interface 'lan'
	option device 'br-lan'
	option proto 'static'
	option ipaddr '192.168.1.1'
	option netmask '255.255.255.0'
	option ip6assign '64'

config device
	option name 'br-guest'
	option type 'bridge'
	list ports 'eth0.2'

config interface
	option device 'br-guest'
	option proto 'static'
	option ipaddr '192.168.2.1'
	option netmask '255.255.255.0'
	option ip6assign '64'

After /etc/init.d/network restart, this is what ip addr returns:

13: br-guest: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc noqueue state UP qlen 1000
    link/ether <identical mac address> brd ff:ff:ff:ff:ff:ff
    inet 192.168.2.1/24 brd 192.168.2.255 scope global br-guest
       valid_lft forever preferred_lft forever
    inet6 fd00:0:1::1/64 scope global noprefixroute
       valid_lft forever preferred_lft forever
    inet6 <identical link-local IPv6 address> scope link
       valid_lft forever preferred_lft forever

15: br-lan: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc noqueue state UP qlen 1000
    link/ether <identical mac address> brd ff:ff:ff:ff:ff:ff
    inet 192.168.1.1/24 brd 192.168.1.255 scope global br-lan
       valid_lft forever preferred_lft forever
    inet6 fd00:0:1:1::1/64 scope global noprefixroute
       valid_lft forever preferred_lft forever
    inet6 <identical link-local IPv6 address> scope link
       valid_lft forever preferred_lft forever

<identical mac address> is eth0's mac address, and <identical link-local IPv6 address> is generated from <identical mac address>.

I guess both br-lan and br-guest take mac address from the first underlying port?

[patrakov]

That's 100% OK, because the link-local IPv6 address must only be unique within the broadcast domain, and each VLAN creates its own broadcast domain.