Last year I wrote a post about my difficulties getting IPv6 to work with the Huawei ME906s-158 WWAN module. I eventually gave up and had it replaced with a module from another manufacturer.

Not long ago, though, I received an e-mail from another ME906s-158 owner who told me that for him, IPv6 worked just fine. That motivated me to brush the dust off my module and try again. This time, I figured it out! Read on for the details.

The Carrier PLMN List

The ME906s-158 comes with a built-in list of nine different PLMN profiles. This list can be managed with proprietary AT command AT^PLMNLIST, which is documented on page 209 of the module’s AT Command Interface Specification.

To interact with the AT command interface, use the option driver. More details on that here.

This is the complete factory default list:

AT^PLMNLIST?

^PLMNLIST: "00000",00000,23106,26207,23802,23806
^PLMNLIST: "20205",26801,20205,26202,26209,27201,27402,50503,54201,53001,40401,40405,40411,40413,40415,40420,40427,40430,40443,40446,40460,40484,40486,40488,40566,40567,405750,405751,405752,405753,405754,405755,405756,20404,20601,20810,21401,21670,22210,22601,23003,23415,24405,24802,27602,27801,28001,28602,28802,29340,42702,60202,62002,63001,63902,64004,64304,65101,65501,90128,23201,28401,64710,46601,42602,22005,41302,29403,50213,50219,21910,25001,27077,52505,23801,40004,42403,46692,52503,73001,24602,24705
^PLMNLIST: "26201",26201,23001,20416,23203,23207,21901,21630,23102,29702,29401,26002,20201,23431,23432
^PLMNLIST: "21403",20610,20801,20802,21403,22610,23101,23430,23433,26803,26003
^PLMNLIST: "50501",50501,50571,50572
^PLMNLIST: "22801",22801,29501
^PLMNLIST: "21407",21405,21407,23402
^PLMNLIST: "99999",24491,24001,23820
^PLMNLIST: "50502",50502 

OK

Each ^PLMNLIST: line represents a single pre-defined PLMN profile, identified by the first MCCMNC number (in double quotes). The "26201" profile is for Deutsche Telekom, the "50501" profile is for Telstra Mobile, and so on.

The rest of the numbers on each line is a list of MCCMNCs that will use that particular profile. For example, if you have a SIM card issued by T-Mobile Netherlands (MCCMNC 20416), then the ME906s-158 will apply the Deutsche Telekom profile ("26201").

Unfortunately, the documentation offers no information on how the PLMN profiles differ and how they change the way the module work.

My provider (Telenor Norway, MCCMNC 24201) is not present in the factory default list. In that case, the module appears to use the "00000" PLMN profile («Generic») as the default, and that one disables IPv6! Clearly, Huawei haven’t read RFC 6540…

In any case, this explains why I failed to make IPv6 work last year, and why it worked fine for the guy who mailed me - his provider was among those that used the Deutsche Telekom PLMN profile by default.

Modifying the Carrier PLMN List

The solution seems clear: I need to add my provider’s MCCMNC to an IPv6-capable PLMN profile. The Deutsche Telekom one would probably work, but "99999" («Generic(IPV4V6)») seems like an even more appropriate choice.

Adding MCCMNCs is done with AT^PLMNLIST=1,"$PLMNProfile","$MCCMNC", like so:

AT^PLMNLIST=1,"99999","24201"

OK

(To remove an MCCMNC, use AT^PLMNLIST=0,"$PLMNProfile","$MCCMNC" instead.)

I can now double check that the "99999" PLMN profile includes 24201 for Telenor Norway:

AT^PLMNLIST="99999"

^PLMNLIST: "99999",24491,24001,23820,24201

OK

To make the new configuration take effect, it appears to be necessary to reset the module. This can be done with the AT^RESET command.

Confirming that IPv6 works

It is possible to query the module directly about IPv6 support in at least two different ways:

AT^IPV6CAP?

^IPV6CAP: 7

OK

AT+CGDCONT=?

+CGDCONT: (0-11),"IP",,,(0-2),(0-3),(0,1),(0,1),(0-2),(0,1)
+CGDCONT: (0-11),"IPV6",,,(0-2),(0-3),(0,1),(0,1),(0-2),(0,1)
+CGDCONT: (0-11),"IPV4V6",,,(0-2),(0-3),(0,1),(0,1),(0-2),(0,1)

OK

The ^IPV6CAP: 7 response means «IPv4 only, IPv6 only and IPv4v6» (cf. page 336 of the AT Command Interface Specification), and the +CDGCONT: responses reveal that the modem is ready to configure PDP contexts using the IPv6-capable IP types. Looking good!

Of course, the only test that really matters is to connect it:

$ mmcli --modem 0 --simple-connect=apn=telenor.smart,ip-type=ipv4v6
successfully connected the modem
$ mmcli --bearer 0                                                                                            
Bearer '/org/freedesktop/ModemManager1/Bearer/0'
  -------------------------
  Status             |   connected: 'yes'
                     |   suspended: 'no'
                     |   interface: 'wwp0s20f0u3c3'
                     |  IP timeout: '20'
  -------------------------
  Properties         |         apn: 'telenor.smart'
                     |     roaming: 'allowed'
                     |     IP type: 'ipv4v6'
                     |        user: 'none'
                     |    password: 'none'
                     |      number: 'none'
                     | Rm protocol: 'unknown'
  -------------------------
  IPv4 configuration |   method: 'static'
                     |  address: '10.169.198.77'
                     |   prefix: '30'
                     |  gateway: '10.169.198.78'
                     |      DNS: '193.213.112.4', '130.67.15.198'
                     |      MTU: '1500'
  -------------------------
  IPv6 configuration |   method: 'static'
                     |  address: '2a02:2121:2c4:7105:5a2c:80ff:fe13:9208'
                     |   prefix: '64'
                     |  gateway: '::'
                     |      DNS: '2001:4600:4:fff::52', '2001:4600:4:1fff::52'
                     |      MTU: '1500'
  -------------------------
  Stats              |          Duration: '59'
                     |    Bytes received: 'N/A'
                     | Bytes transmitted: 'N/A'

Success!