Avatar for Username

Search Support

Avoid support scams. We will never ask you to call or text a phone number or share personal information. Please report suspicious activity using the “Report Abuse” option.

Learn More

This thread was archived. Please ask a new question if you need help.

Does Firefox prefer Private RFC 1918 IPv4 Addresses over public IPv6 Addresses?

  • No replies
  • 1 has this problem
  • 12 views
hcuk94
hcuk94
more options

I have a bunch of DNS records for servers etc which resolve to the 2 IP addresses of each device; a public IPv6 address and a private (10.0.0.0/8) IPv4 address.

I am finding that where I do not have IPv4 connectivity (i.e. I am not behind the same NAT as the device), Firefox tries to connect and eventually times out. If I remove the IPv4 (A) record from the DNS name, then it connects absolutely fine over IPv6.

I am aware of how Firefox is designed to handle IPv4 vs IPv6 connectivity where the fastest response time will be favoured. I have verified that in my case, connecting to the 'IPv6 test' websites always favours IPv6 - so my config is good.

So my question is, if a DNS name returns a public IPv6 and a private IPv4 address, will Firefox favour the IPv4 address on the basis of it being 'internal'? And if so, is there any way to disable this?

(Firefox 97.0 on Windows 10 20H2)

Thanks in advance.

I have a bunch of DNS records for servers etc which resolve to the 2 IP addresses of each device; a public IPv6 address and a private (10.0.0.0/8) IPv4 address. I am finding that where I do not have IPv4 connectivity (i.e. I am not behind the same NAT as the device), Firefox tries to connect and eventually times out. If I remove the IPv4 (A) record from the DNS name, then it connects absolutely fine over IPv6. I am aware of how Firefox is designed to handle IPv4 vs IPv6 connectivity where the fastest response time will be favoured. I have verified that in my case, connecting to the 'IPv6 test' websites always favours IPv6 - so my config is good. So my question is, if a DNS name returns a public IPv6 and a private IPv4 address, will Firefox favour the IPv4 address on the basis of it being 'internal'? And if so, is there any way to disable this? (Firefox 97.0 on Windows 10 20H2) Thanks in advance.