ipv6 configuration problems in Chinese universities

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975216802@qq.com
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Joined: 28 Feb 2023
Posts: 8

PostPosted: Tue Feb 28, 2023 18:02    Post subject: ipv6 configuration problems in Chinese universities Reply with quote
Hello everyone,I’m a student from Beijing University of Chemical Technology. My device can’t work fine with ipv6,I have spent a lot of time in it, but haven’t find the correct way. I need your help to fix my network.

My router is Linksys EA6500 and I always upgrade to the latest release.(now is r51887)

By the way, in my school, ipv6 is free so my laptop and phones can access to ipv6 network without any configuration if connect directly. The router can easily access to ipv6 in both “Native from ISP” and “DHCPv6” mode too, but devices under the router can’t.

The first idea is ipv6 pass through,I use the script like this
Code:
 
cd /lib/modules/4.4.302-st37/
/sbin/insmod ebtables
sleep 5
/sbin/insmod ebtable_broute
sleep 5
/sbin/insmod ebtable_filter
sleep 5
brctl addif br0 vlan2
ebtables -t broute -A BROUTING -p IPv6 -j ACCEPT
ebtables -t broute -A BROUTING -p ! IPv6 -i vlan2 -j DROP


Then I find that ipv6 is ok but ipv4 is broken. I use ssh to connect the server through ipv4 and about every 10~20 seconds it will disconnect.
What should I do to fix this?


I tried some methods like radvd and dnsmasq too, they had other problems,I will talk about it later.
If any other information is needed, please tell me.
Thanks.

---------------------------------------------------------------------------------------------------------
---------------------------------------------update at 2023/03/01----------------------------------------

The second idea is radvd, I add this to Custom Configuration:
Code:

interface vlan2 {
   AdvSendAdvert on;
   prefix 2001:da8:237:951::/64{
    AdvOnLink on;
    AdvAutonomous on;
   };
};

I also change "vlan2" to "vlan1","br0".
none of these works.


Last edited by 975216802@qq.com on Wed Mar 01, 2023 9:56; edited 1 time in total
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Per Yngve Berg
DD-WRT Guru


Joined: 13 Aug 2013
Posts: 6858
Location: Romerike, Norway

PostPosted: Tue Feb 28, 2023 18:30    Post subject: Reply with quote
You must obtain a Delegated Prefix from the university.

If a wide dhcp6 server is avalible, set the IPv6 Configuration to PD.
975216802@qq.com
DD-WRT Novice


Joined: 28 Feb 2023
Posts: 8

PostPosted: Wed Mar 01, 2023 3:35    Post subject: Reply with quote
Per Yngve Berg wrote:
You must obtain a Delegated Prefix from the university.

If a wide dhcp6 server is avalible, set the IPv6 Configuration to PD.

I am sorry for not giving you a prompt reply.
I don't know whether the "wide dhcp6 server" is the default one. So I tried this:


However, the server under the router don't have any correct address.
Code:

snc@poweredgt5:~$ ifconfig | grep inet6
        inet6 fe80::42:e1ff:fea7:48fd  prefixlen 64  scopeid 0x20<link>
        inet6 fe80::42:60ff:fe7c:df2c  prefixlen 64  scopeid 0x20<link>
        inet6 fe80::210:18ff:fe60:47f7  prefixlen 64  scopeid 0x20<link>
        inet6 ::1  prefixlen 128  scopeid 0x10<host>
        inet6 fd42:4b6:b9d:d21d::1  prefixlen 64  scopeid 0x0<global>
        inet6 fe80::102d:5fff:fe33:eb2b  prefixlen 64  scopeid 0x20<link>
        inet6 fe80::f8c7:85ff:fed9:7ebf  prefixlen 64  scopeid 0x20<link>
        inet6 fe80::4836:8bff:fea3:982b  prefixlen 64  scopeid 0x20<link>
        inet6 fe80::e475:feff:fec7:2008  prefixlen 64  scopeid 0x20<link>
        inet6 fe80::5842:10ff:fe75:5791  prefixlen 64  scopeid 0x20<link>
        inet6 fe80::2e65:6a2:e0aa:f642  prefixlen 64  scopeid 0x20<link>
Per Yngve Berg
DD-WRT Guru


Joined: 13 Aug 2013
Posts: 6858
Location: Romerike, Norway

PostPosted: Wed Mar 01, 2023 6:51    Post subject: Reply with quote
What is "ifconfig br0" showing?
975216802@qq.com
DD-WRT Novice


Joined: 28 Feb 2023
Posts: 8

PostPosted: Wed Mar 01, 2023 10:02    Post subject: Reply with quote
Per Yngve Berg wrote:
What is "ifconfig br0" showing?

Code:
root@DD-WRT:~# ifconfig br0
br0       Link encap:Ethernet  HWaddr C8:D7:19:AB:72:F9 
          inet addr:192.168.1.1  Bcast:192.168.1.255  Mask:255.255.255.0
          inet6 addr: fe80::cad7:19ff:feab:72f9/64 Scope:Link
          UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
          RX packets:7155 errors:0 dropped:0 overruns:0 frame:0
          TX packets:3213 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:1000
          RX bytes:949801 (927.5 KiB)  TX bytes:1125669 (1.0 MiB)
975216802@qq.com
DD-WRT Novice


Joined: 28 Feb 2023
Posts: 8

PostPosted: Wed Mar 01, 2023 10:09    Post subject: Reply with quote
Per Yngve Berg wrote:
You must obtain a Delegated Prefix from the university.

If a wide dhcp6 server is avalible, set the IPv6 Configuration to PD.


I find that ::/64 prefix is the same in my room, the router and other devices share it.
So I think I should use ipv6 pass through.
userrox
DD-WRT Novice


Joined: 11 May 2019
Posts: 16

PostPosted: Thu Mar 02, 2023 5:33    Post subject: Reply with quote
If you pass through aren't you essentially bridging your WAN to the LAN for IPv6 packets? That seems like a bad idea to me if all of dd-wrt's firewall and routing functionality will be bypassed too. I'm not an expert, but my suggestion would be to advertise a completely different prefix (ULA?) on br0 using dnsmasq and then use NAT66 (ip6tables MASQUERADE target) to share the IPv6 global address you can obtain on the WAN interface.
Per Yngve Berg
DD-WRT Guru


Joined: 13 Aug 2013
Posts: 6858
Location: Romerike, Norway

PostPosted: Thu Mar 02, 2023 8:32    Post subject: Reply with quote
ULA adresses is in the range fc00::/7
975216802@qq.com
DD-WRT Novice


Joined: 28 Feb 2023
Posts: 8

PostPosted: Thu Mar 02, 2023 12:03    Post subject: Reply with quote
userrox wrote:
If you pass through aren't you essentially bridging your WAN to the LAN for IPv6 packets? That seems like a bad idea to me if all of dd-wrt's firewall and routing functionality will be bypassed too. I'm not an expert, but my suggestion would be to advertise a completely different prefix (ULA?) on br0 using dnsmasq and then use NAT66 (ip6tables MASQUERADE target) to share the IPv6 global address you can obtain on the WAN interface.

Thank you for your advice, but your method seem not satisfy my demand.

NAT66 can't easily use port forwarding,and I have many virtual machines and many freshman use it to learn linux system.
Pass through may have some safety concern, but I think I can take care.
Per Yngve Berg
DD-WRT Guru


Joined: 13 Aug 2013
Posts: 6858
Location: Romerike, Norway

PostPosted: Thu Mar 02, 2023 15:20    Post subject: Reply with quote
You can connect it as a WAP (LAN-LAN).

Otherwise you have to obtain a Global Scope Address Prefix from the University.
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