DHCPv6 by default on 3750?

[tylerhall]

I have a very strange problem.  I gave one of my interfaces a IPv6 address the other day and now all of my servers have IPv6 addresses in that subnet.

I'm reading about "ipv6 nd suppress-ra" and I think that's what I need to disable but that's not a valid command on the 3750. 

Is there a way to disable this 'automatic IP giving out' thing that I have going on?

[Harold Ritter · Accepted solution]

Hi Tyler,

This is actually not dhcpv6 but rather Stateless Adress Autoconfiguration (SLACC) that you are seeing. SLAAC is enabled by default when "ipv6 unicast-routing" is configured and that an ipv6 address is assigned to an interface.

Try using "ipv6 nd ra suppress all" to completely disable the RA on a specific interface.

Hope this helps

[tylerhall]

Thanks.  I have a "ipv6 nd ra suppress" under the interface which I've applied.

[Harold Ritter]

Hi Tyler,

Bear in mind that the "ipv6 nd ra suppress" without the "all" keyword will suppress the periodic RA from the router but will not suppress the RA sent in response to a RS message from the workstation. The "all" keyword is relatively recent and might not be available in the version of code you are currently running. One of the workaround is to use an ACL to block incoming RS on the specific interface.

Regards

[tylerhall]

Thanks Harold.

I just upgraded to the newest firmware (12.2(55)SE7) but I still don't have a 'all' under suppress.

Any ideas?

[Harold Ritter]

Hi Tyler,

The support for the "all" keyword started in 12.2(58)SE1. As a workaround, you could use either one of the following commands under the specific interface:

ipv6 nd prefix [prefix] no-autoconfig

or

ipv6 nd prefix [prefix] no-advertise

Hope this helps