Block / Disable IPv6 link-local

[CobbyJ]

Hello,

I am trying to run Ipv6 via our network but the cisco 3750 vlan has a local link and is showing up as a gateway on the a connected client on that vlan.

can i stop the link-local fe80 ipv6 ip's from being enabled on the vlan and showing up as a router?

Kind Regards,

Chris

[Harold Ritter]

Hi @CobbyJ ,

If you do not want the 3750 to act as an IPv6 router, you should disable "ipv6 unicast-routing".

no ipv6 unicast-routing

Regards,

[CobbyJ]

Hello.

That is not possible as it uses OSPFv3 and requires ipv6 routing.

I just do not want it to advertise ipv6 from a local link and use it as a gateway.

I tried a few different things to prevent it but no luck so far.

[Harold Ritter]

How about disabling IPv6 on the vlan interface with the "no ipv6 enable" command?

Regards,

[Peter Paluch]

Hi @CobbyJ , hi @Harold Ritter ,

So, to sum up: Your Cat3750 uses OSPFv3, hence you cannot disable IPv6 routing and cannot disable IPv6 on its interfaces. You still need to prevent the Cat3750 to announce itself as a possible gateway to the end hosts attached to its SVIs. Correct?

To prevent hosts from considering the Cat3750 as an IPv6 default gateway, it needs to stop sending out Router Advertisements (RAs). This way, you can keep the IPv6 routing and OSPFv3 there, but to the end hosts, the Cat3750 will stop announcing itself as a potential IPv6 default gateway.

For this, try configuring the ipv6 nd ra suppress all command on the SVI for the affected VLAN. This command will prevent sending out all advertisements, both periodic and solicited, from that SVI. Note that the end hosts will have the information about the IPv6 default gateway cached for some time so you will need to reload them or at least restart their NIC drivers.

Please let us know if this worked!

Best regards,
Peter

[Harold Ritter]

Hi @Peter Paluch ,

The original poster indicated that he only had a link local address on the interface. My suggestion was just that if this interface was not going to be used for IPv6, it would just be safer to disable it altogether on that interface. Your suggestion to stop RA from being sent will definitely work too.  

I guess it is up to the original poster to tell us what he is trying to achieve.

Regards,

[Peter Paluch]

Hi Harold,

I hope I did not respond in any inappropriate way. If I did, my sincere apologies!

I agree that the information from @CobbyJ is coming in pieces and always changes the conditions a little. Either way, let us see if any of the suggestions offered so far would be applicable for his environment.

Best regards and respects,
Peter

[Harold Ritter]

Hi Peter,

It is nice to hear from you. You suggestion is right on the money. We do not know exactly what is the situation and it is therefore difficult to say from the info we got so far what solution best suits the need of the original poster. 

Stay safe,