IPv6 DHCP client over PPP receiving Address incorrectly but PD working fine

RouterOS General
1

Hi!

I noticed that using DHCPv6 (over an already established PPP connection) to request an Address and a delegated Prefix, it seems that ROS ignores the RFC8415 and gives the interface a /64 length. The packet sniffer shows an Option type 3 carrying the address without a prefix/length (attached the Wireshark segment). The RFC8415 states in page 104 sect. 21.6:

A client MUST NOT form an implicit prefix with a length other than 128 for this address. A 16-octet field.

From the routerboad itself I can see the address and the prefix correctly received:

/ipv6 dhcp-client> print detail 
Flags: D - dynamic, X - disabled, I - invalid 
 0    interface=pppoe-out2 status=bound duid="0xxxxxxxxx" dhcp-server-v6=fe80::xxxxxx request=address,prefix add-default-route=yes default-route-distance=1 use-peer-dns=yes pool-name="pool1" 
      pool-prefix-length=64 prefix-hint=::/0 dhcp-options="" prefix=2a00:xxx:yyy:zzz::/64, 2d23h48m6s address=2a00:www:kkk::1, 2d23h48m6s

But on the interface:

/ipv6 address> print detail 
Flags: X - disabled, I - invalid, D - dynamic, G - global, L - link-local 
[...]
11 DG address=2a00:www:kkk::1/64 from-pool="" interface=pppoe-out2 actual-interface=pppoe-out2 eui-64=no advertise=no no-dad=no

Where does the /64 come from?

Thanks!
addrv6.PNG

2

Do you actually need interface address for PPP interface? For me (already established PPPoE) it is enough to request prefix (I’m getting /56), one address (from pool) assigned to LAN interface … and IPv6 works both for router and LAN machines. For routing link-local address on pppoe interface is enough.

3

Oh, sure you’re right. I’m just trying to understand the technology and if it’s me or ROS not to get it :slight_smile: