Device get incorrect ipv6 and dns

[serial115200]

I change the IPv6 prefix from 3001::/64 to 4001::/64. my computer get two IPv6 address, 3001::9450:5231:6c39:267a and 4001::9450:5231:6c39:267a, and dns is still 3001::1, then i can't access internet.

here is my route info.

the ipv6 prefix assignment has been removed from netifd database of lan interface, and preferred_lft has been set 0 sec. this is the design, see the clarification

/ # ip -6 addr show br-lan
37: br-lan: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 state UP qlen 1000
    inet6 4001::1/64 scope global noprefixroute
       valid_lft forever preferred_lft forever
    inet6 3001::1/64 scope global deprecated dynamic noprefixroute
       valid_lft 5367sec preferred_lft 0sec
    inet6 fe80::219:c7ff:fe22:100/64 scope link
       valid_lft forever preferred_lft forever
/ #
/ #
/ # ifconfig br-lan
br-lan    Link encap:Ethernet  HWaddr 00:19:C7:22:01:00
          inet addr:192.168.3.1  Bcast:192.168.3.255  Mask:255.255.255.0
          inet6 addr: fe80::219:c7ff:fe22:100/64 Scope:Link
          inet6 addr: 4001::1/64 Scope:Global
          inet6 addr: 3001::1/64 Scope:Global
          UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
          RX packets:266654 errors:0 dropped:0 overruns:0 frame:0
          TX packets:260117 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:1000
          RX bytes:45074177 (42.9 MiB)  TX bytes:116549902 (111.1 MiB)

/ #
/ # ubus call network.interface.lan status
{
        "up": true,
        "pending": false,
        "available": true,
        "autostart": true,
        "dynamic": false,
        "uptime": 23956,
        "l3_device": "br-lan",
        "proto": "static",
        "device": "br-lan",
        "updated": [
                "addresses"
        ],
        "metric": 0,
        "dns_metric": 0,
        "delegation": true,
        "ipv4-address": [
                {
                        "address": "192.168.3.1",
                        "mask": 24
                }
        ],
        "ipv6-address": [

        ],
        "ipv6-prefix": [

        ],
        "ipv6-prefix-assignment": [
                {
                        "address": "4001::",
                        "mask": 64,
                        "local-address": {
                                "address": "4001::1",
                                "mask": 64
                        }
                }
        ],
        "route": [

        ],
        "dns-server": [

        ],
        "dns-search": [

        ],
        "inactive": {
                "ipv4-address": [

                ],
                "ipv6-address": [

                ],
                "route": [

                ],
                "dns-server": [

                ],
                "dns-search": [

                ]
        },
        "data": {

        }
}

here is my pc info

I do another test,so prefix is 4001::/64 and 5001::/64

[vgaetera]

You can advertise custom resolvers:

• Use a ULA prefix for DNSv6
• Use a public DNS provider

By the way, IPv6 is served by odhcpd, not dnsmasq.

[serial115200]

Thank for your reply.

your solution solve my problem.

I have another question.why IPv6 is served by odhcpd, not dnsmasq. dnsmasq-full can also provide services. Is there any consideration, or good thing about odhcpd, or dnsmasq-full is too big .

[vgaetera]

https://forum.archive.openwrt.org/viewtopic.php?id=68148#p341659

odhcpd does much more than just ipv6 dhcp. In addition to dhcpv6 it provides all RA functionality -
accepts RAs (instead of default kernel built-in mechanism which is not used in openwrt),
can act as RA server and can do RA/NDP relaying (which is itself very specific function).

Its well integrated with openwrt's network management engine - netifd - and communicates with it directly via ubus interface. So, odhcpd is openwrt specific daemon written in C to meet all its specific needs. Initially devs wrote shell scripts for all the stuff and used well known commands and daemons but later they started to write native daemons because of increased stability and reliability.

Better question - why still dnsmasq used as dhcpv4 server. Odhcpd contain dhcpv4 code. May be because dnsmasq is more configurable and for older versions compatibility. Odhcpd is good thing for most uses but there're scenarios where its not enough flexible and radvd have to be used.