DHCPv6 assigns the same IPv6 to multiple hosts

[cosmintrica]

Hello everyone,

I created this Packet Tracer with IPv6 pool created on R1 and R2 used as a relay, with ipv6 server command issued on interface g0/0/0.10

Automatically assigning of ipv6 works , but the 2 hosts that are in vlan10 have the same exact IPv6 address.
I am just starting to study networking and I wanna understand why this is happening, can someone help me?

Thank you in advance!

[balaji.bandi]

that should not happend as long as you configured as expected :

check the video and check the config :

https://www.youtube.com/watch?v=Vk28BQFr7z8

[cosmintrica]

Thank you!
Can you maybe take a look at my PKT configuration, maybe something small is causing the issue?
I configured it on the router, not on an actual server.

[Harold Ritter · Accepted solution]

Hi @cosmintrica ,

The IPv6 addresses you are currently getting on vlan10-pc1 and vlan10-pc2 come from SLAAC, not from dhcpv6. There are a few things that need to be changed in your configuration for dhcpv6 to work.

1. Configuring "ip dhcp server" on R2 makes it a server, not a relay. The relay fonction is not available on Packet Tracer as far as I know. The ipv6 dhcp pool VLAN10 should be configured on R2. 

2. configure the following on R2 gi0/0/0.10

ipv6 nd other-config-flag

ipv6 nd managed-config-flag

3. Please remove the link local configuration (fe80::1) on vlan10-pc1 and vlan10-pc2, as it conflicts with what is configured on R2. 

I am attaching the .pkt file with the changes.

Regards,

[cosmintrica]

You are amazing, thank you so much for the explanation.
One more question, DHCPv6 relay does not work, but DHCPv4 does?
In Packet Tracer I mean. Because DHCPv4 is configured on R1 and seem to work.

[Harold Ritter]

Hi @cosmintrica ,

The relay function is supported for DHCP, but not for DHCPv6.

Router(config-if)#ipv6 dhcp ?

client Act as an IPv6 DHCP client

server Act as an IPv6 DHCP server

Regards,