# Enable IPv6 router advertisements



## rforberger (Aug 5, 2021)

Hi,

I have enabled router advertisements on my FreeBSD 13.0 amd64 machine, but I am not getting a global IPv6 address.

My rc.conf looks like the following:


```
ifconfig_DEFAULT="SYNCDHCP mtu 1460 accept_rtadv"
ipv6_activate_all_interfaces="YES"
```

I am receiving router advertisements on a Linux machine on the same network segment from the router advertisement daemon.
But on FreeBSD I am not getting an address.

Can you help me what I am doing wrong?

Thank you in advance.

Best regards,
rforberger


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## SirDice (Aug 6, 2021)

Does `rtsol <interface>` get you an address? Does the interface have a link-local (fe80::) address?

Note that the standard MTU for ethernet is 1500. There's no need to set this to 1460. You may have seen 1460 somewhere but this is the TCP MSS, not the MTU. TCP MSS is MTU minus 20 bytes for the IP headers and minus 20 bytes for the TCP header, i.e. 1500-20-20=1460.


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## rforberger (Aug 6, 2021)

Thanks, but I found it out.

I had to install dhcp6, using dhcp6c to get the IP.

I need this MTU because I am running on a cloud provider.


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