PPP IPv6 with SLAAC not working (lab)

[insideshell]

Hello,

I'm trying to get familiar with PPP IPv6 using SLAAC (and later DHCPv6).
So I set up a very simple GNS3 lab with two C2691 IOS images (old but it should be enough):

I'm using a serial link so that I do not need the PPPoE configuration items (BBA group, virtual template, dialer — but actually the same problem occurs on a PPPoE link).

Here are my configurations:

---

R1#show run
!
ipv6 unicast-routing
!
interface Loopback0
 no ip address
 ipv6 address 2001:DB8:12FF::1/128
!
interface Serial1/0
 no ip address
 encapsulation ppp
 ipv6 unnumbered Loopback0
 ipv6 enable
 no ipv6 nd ra suppress
 peer default ipv6 pool IPV6-POOL
!
ipv6 local pool IPV6-POOL 2001:DB8:5AB:10::/60 64
!
R1#show ipv6 interface brief
Serial1/0 [up/up]
FE80::C201:51FF:FE6A:0

---

R2#show run
!
ipv6 unicast-routing
!
interface Serial1/0
 no ip address
 encapsulation ppp
 ipv6 address autoconfig
 ipv6 enable
!
From the Cisco guide: "The ipv6 address autoconfig command causes the device to perform IPv6 stateless address auto-configuration to discover prefixes on the link and then to add the EUI-64 based addresses to the interface. Addresses are configured depending on the prefixes received in Router Advertisement (RA) messages."

---

Problem is: my RA messages from R1 to R2 do NOT contain the prefix option (see below, full capture attached). It seems R1 does not allocate a /64 IPv6 prefix from the IPV6-POOL.

As you can see, there is only the MTU option but not the Prefix Information option used for SLAAC (RFC 4861).
I also tried this from the official guide without luck.

Any help would be appreciated!

Thanks.

[insideshell]

Be noted it works by forcing the prefix to advertise:

---

R1#sho run int s1/0
!
interface Serial1/0
 no ip address
 encapsulation ppp
 ipv6 unnumbered Loopback0
 ipv6 enable
 peer default ipv6 pool IPV6-POOL
 ipv6 nd prefix 2001:DB8:5AB:10::/64
 no ipv6 nd ra suppress
!
ipv6 local pool IPV6-POOL 2001:DB8:5AB:10::/60 64
!

---

Now, the RA message contains the prefix option:

And in R2:

---

R2#sho ipv6 int br
Serial1/0 [up/up]
FE80::C202:51FF:FE79:0
2001:DB8:5AB:10:C202:51FF:FE79:0

---

As expected, R2 performed the SLAAC based on the RA prefix.
But still no way to get it working using my IPV6-POOL, if someone has a clue.

Thanks.

[insideshell]

Actually I have the same issue on a real CISCO1941/K9.
So I think I'm missing some configurations items.
This time I did exactly as per Configuring PPPoE on IPv6 guide.
Here are my configurations (now using PPPoE):

---

R1#show run
!
ipv6 unicast-routing
!
bba-group pppoe GROUPA
 virtual-template 1
!
interface Loopback1
 no ip address
 ipv6 address 2001:DB8:2::1/40
!
interface GigabitEthernet0/0
 no ip address
 pppoe enable group GROUPA
!
interface Virtual-Template1
 no ip address
 peer default ipv6 pool pool1
 ipv6 unnumbered Loopback1
 ipv6 enable
 no ipv6 nd ra suppress
!
ipv6 local pool pool1 2001:DB8:1200::/40 48
!

---

R2#show run
!
interface FastEthernet0/0
 no ip address
 pppoe enable group global
 pppoe-client dial-pool-number 1
!
interface Dialer1
 no ip address
 encapsulation ppp
 dialer pool 1
 ipv6 address autoconfig default
 ipv6 enable
!

---

But again, no Prefix in the RA messages.
Any thoughts?
Thanks!

[Harold Ritter]

It looks like you and the original poster might be hitting this bug. Could you please upgrade to a fixed version, as indicated in the following link and see if it fixes the issue.

https://bst.cloudapps.cisco.com/bugsearch/bug/CSCtl17505

Regards,

[insideshell]

Unfortunately, it looks like I didn't have the permission to view the bug report:

Insufficient Permissions to View Bug
This bug contains proprietary information and is not yet publicly available.
You may find useful information within theCisco Community

I am logged in with my Cisco account which is associated with my company contract.
Thanks for your answer.

[Harold Ritter]

It looks like it is not externally available. What version of IOS are you running?

Could you also provide a "show ipv6 interface Virtual-Access <interface and subinterface number>".

Regards,

[insideshell]

I'm using C1941 C1900-UNIVERSALK9-M, Version 15.2(4)M3, RELEASE SOFTWARE (fc2)

Here is the output:

Router#show ipv6 interface virtual-access 1.1
Virtual-Access1.1 is up, line protocol is up
IPv6 is enabled, link-local address is FE80::B2FA:EBFF:FED6:4320
No Virtual link-local address(es):
Interface is unnumbered. Using address of Loopback0
No global unicast address is configured
Joined group address(es):
FF02::1
FF02::2
FF02::1:FFD6:4320
MTU is 1492 bytes
ICMP error messages limited to one every 100 milliseconds
ICMP redirects are enabled
ICMP unreachables are sent
ND DAD is enabled, number of DAD attempts: 1
ND reachable time is 30000 milliseconds (using 30000)
ND advertised reachable time is 0 (unspecified)
ND advertised retransmit interval is 0 (unspecified)
ND router advertisements are sent every 200 seconds
ND router advertisements live for 1800 seconds
ND advertised default router preference is Medium
Hosts use stateless autoconfig for addresses.

Thanks.

[Harold Ritter]

This seems to be the bug you hit. Could you please upgrade to some more recent IOS version and see that it fixes the issue.

Regards,

[insideshell]

I cannot upgrade, it seems we don't have a newer image for this model.
But we have VIRL and I tested with an IOSv Software (VIOS-ADVENTERPRISEK9-M), Version 15.7(3)M3.
I am encountering the same issue: no IPv6 allocation from the pool.
That's why I'm starting to think maybe I missed some configuration items...

[Harold Ritter · Accepted solution]

Hi,

Can you change the following in your configuration.

1. Enable chap authentication between the client and the server.

2.. Change your pool as follow:

from ipv6 local pool pool1 2001:DB8:1200::/40 48 to ipv6 local pool pool1 2001:DB8:1200::/40 64

This should fix it.

Regards,

I tried

[insideshell]

It worked with the CHAP authentication enabled!
I also tried with the PAP authentication and it worked as well!
I don't really understand why authentication is mandatory for IPv6 (that's why I didn't enable it before).
For an IPv4 pool, it works without any authentication method.
Actually, it worked without changing the pool (even if I read in one of your posts that SLAAC supports only /64, but /64 was my original need).

EDIT: about the pool, it is indeed needed to allocate a /64 and not a /48, otherwise SLAAC does not work on the client side.

Many thanks Sir!