IPv6 Router Advertisements from Other Interfaces

I have a interface that has a default configuration & a VLAN associated with it

show interfaces ethernet eth1
 address 172.16.0.1/16
 address fc00:1::1/64
 description LAN
 vif 25 {
     address 192.168.99.1/24
     address fc00:2::1/64
     description GUEST
 }

I also have router-advertisements configured:

show service router-advert
 interface eth1 {
     default-lifetime 300
     default-preference high
     hop-limit 64
     interval {
         max 30
     }
     name-server fc00:1::1
     prefix fc00:1::/64 {
         preferred-lifetime 300
         valid-lifetime 900
     }
     reachable-time 900000
     retrans-timer 0
 }
 interface eth1.25 {
     default-lifetime 300
     default-preference high
     hop-limit 64
     interval {
         max 30
     }
     name-server 2606:4700:4700::1111
     name-server 2606:4700:4700::1001
     prefix fc00:2::/64 {
         preferred-lifetime 300
         valid-lifetime 900
     }
     reachable-time 900000
     retrans-timer 0
 }

Everything is working - but the curious thing I’m seeing is that on a device on the LAN subnet, it’s seeing router advertisements for the GUEST interface as well as LAN. As a result, one of my devices is getting addresses in both.

The IPv4 side of things is working as expected.

I assumed that because I’m scoping things by the interface in the router-advertisement configuration, that it would only send that prefix out on that interface. Is this intended behaviour or if not, how can I ensure that the advertisements from GUEST don’t go to LAN and vice versa.

I’m on 1.4, commit ID a03b5dbd3e3699

I think this should not be the case as GUEST RAs will get tagged with vlan 25.

vyos@vyos# sudo tcpdump -n -i  eth1 -e -vvv
tcpdump: listening on eth1, link-type EN10MB (Ethernet), snapshot length 262144 bytes
05:25:44.533934 0c:ef:1a:2c:00:01 > 33:33:00:00:00:01, ethertype IPv6 (0x86dd), length 150: (flowlabel 0x05e77, hlim 255, next-header ICMPv6 (58) payload length: 96) fe80::eef:1aff:fe2c:1 > ff02::1: [icmp6 sum ok] ICMP6, router advertisement, length 96
	hop limit 64, Flags [none], pref high, router lifetime 300s, reachable time 900000ms, retrans timer 0ms
	  prefix info option (3), length 32 (4): fc00:1::/64, Flags [onlink, auto], valid time 900s, pref. time 300s
	    0x0000:  40c0 0000 0384 0000 012c 0000 0000 fc00
	    0x0010:  0001 0000 0000 0000 0000 0000 0000
	  rdnss option (25), length 24 (3):  lifetime 30s, addr: fc00:1::1
	    0x0000:  0000 0000 001e fc00 0001 0000 0000 0000
	    0x0010:  0000 0000 0001
	  mtu option (5), length 8 (1):  1500
	    0x0000:  0000 0000 05dc
	  source link-address option (1), length 8 (1): 0c:ef:1a:2c:00:01
	    0x0000:  0cef 1a2c 0001
	  advertisement interval option (7), length 8 (1):  30000ms
	    0x0000:  0000 0000 7530
05:25:46.533675 0c:ef:1a:2c:00:01 > 33:33:00:00:00:01, ethertype 802.1Q (0x8100), length 170: vlan 25, p 0, ethertype IPv6 (0x86dd), (flowlabel 0x05e77, hlim 255, next-header ICMPv6 (58) payload length: 112) fe80::eef:1aff:fe2c:1 > ff02::1: [icmp6 sum ok] ICMP6, router advertisement, length 112
	hop limit 64, Flags [none], pref high, router lifetime 300s, reachable time 900000ms, retrans timer 0ms
	  prefix info option (3), length 32 (4): fc00:2::/64, Flags [onlink, auto], valid time 900s, pref. time 300s
	    0x0000:  40c0 0000 0384 0000 012c 0000 0000 fc00
	    0x0010:  0002 0000 0000 0000 0000 0000 0000
	  rdnss option (25), length 40 (5):  lifetime 30s, addr: 2606:4700:4700::1111 addr: 2606:4700:4700::1001
	    0x0000:  0000 0000 001e 2606 4700 4700 0000 0000
	    0x0010:  0000 0000 1111 2606 4700 4700 0000 0000
	    0x0020:  0000 0000 1001
	  mtu option (5), length 8 (1):  1500
	    0x0000:  0000 0000 05dc
	  source link-address option (1), length 8 (1): 0c:ef:1a:2c:00:01
	    0x0000:  0cef 1a2c 0001
	  advertisement interval option (7), length 8 (1):  30000ms
	    0x0000:  0000 0000 7530