Catalyst 3650 IOS-XE 16.8.1a DHCPv6 relay issues?

[andrew.butterworth]

I have a small layer-3 Lab network consisting of a Catalyst 3650 with IP Services license and several Catalyst 3560's with IP services.  I have some ESXi servers and running on these are various servers - including some Windows 2012R2 DHCP servers.  I have configured stateless autoconfig for IPv6 addresses and stateful other config (DHCPv6 for DNS etc) on various VLANs with DHCPv6 relay configured to forward the DHCPv6 requests to the Windows 2012R2 DHCP servers.

I have hit an issue with the Catalyst 3650 (IOS-XE 16.8.1a) in that it doesn't accept the DHCPv6 replies and the clients fail to get the other information from the DHCP servers.  The same configurations work fine on the Catalyst 3560s (IOS 15.0(2)SE11).

interface Vlan30
 ip address 192.168.5.30 255.255.255.224
 ip helper-address 192.168.1.1
 ip helper-address 192.168.2.1
 no ip redirects
 no ip proxy-arp
 ip pim sparse-mode
 ipv6 address Lab-48 ::665E:0:0:0:FE/64
 ipv6 enable
 ipv6 nd other-config-flag
 no ipv6 redirects
 ipv6 dhcp relay destination 2001:1:1:1:192:168:1:1
 ipv6 dhcp relay destination 2001:1:1:2:192:168:2:1

I have masked the IPv4 & IPv6 addresses, however the logic is sound.  This configuration on the 3560s works and debugging ipv6 dhcp relay shows ' IPv6 DHCP_RELAY: Packet forwarded to xxx' and subsequent 'IPv6 DHCP: Received RELAY-REPLY from xxx' messages.  However the Catalyst 3650 never shows the 'IPv6 DHCP: Received RELAY-REPLY from xxx' messages and the clients never get the options from the DHCPv6 server.

I found a post on Reddit discussing the exact same issue, however the thread is archived.

https://www.reddit.com/r/Cisco/comments/8pebmw/ipv6_issue_my_relayreply_packets_never_make_it/

I am reluctant to upgrade beyond 16.8.1a due to the enforced Smart Licensing (the 3650 was purchased with IP Services (PID: WS-C3650-48PQ-E), however it is often wiped and rebuilt and generally in isolation in the lab).

Any ideas?

[andrew.butterworth]

After playing around with all the IPv6 DHCP relay configuration options in the CLI I gave up and decided to upgrade the IOS-XE to 16.9.3a and bite the bullet with smart licensing - you get 90-days to sort it out...

After a reboot all the IPv6 hosts that didn't have IPv6 DNS servers learned them via DHCPv6....  This is therefore obviously a bug in 16.8.1a which I doubt will get fixed in the 16.8x train.

Smart Licensing worked...  We have a couple of Smart Accounts (one is Dev) and I have a Virtual Account in this.  I created a token, added it to the 3650 and did a 'license smart conversion start' and crossed my fingers...

It initiated the conversion and an hour later it changed from non-compliant to authorized.  Checking on the smart licensing portal I can see:

1 new "C3650_48_Ipserv" perpetual license was added to the Virtual Account "XXXXXXXX" via a Device led conversion request from the Product Instance "UDI_PID:WS-C3650-48PQ; UDI_SN:FDxxxxxxxxP; "

I have some Catalyst 9200 & 9300's to install for a customer in a couple of weeks and Smart Licensing is the ONLY option on these as the initial release of IOS-XE is 16.9..  Ho hum...