# Issues when attempting to backend from IPv4 to IPv6

**URL:** <https://discourse.haproxy.org/t/issues-when-attempting-to-backend-from-ipv4-to-ipv6/11280>\
**Category:** Help!\
**Created:** [October 16, 2024, 4:50pm UTC](https://discourse.haproxy.org/t/issues-when-attempting-to-backend-from-ipv4-to-ipv6/11280 "2024-10-16T16:50:14Z")\
**Posts on this page:** 1\
**Page:** 1

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**Author:** ![cumbria](https://avatars.discourse-cdn.com/v4/letter/c/8c91f0/32.png) [@cumbria](https://discourse.haproxy.org/u/cumbria)\
**Post date:** [October 16, 2024, 4:50pm UTC](https://discourse.haproxy.org/t/issues-when-attempting-to-backend-from-ipv4-to-ipv6/11280/1 "2024-10-16T16:50:14Z")

</div>

Hello,

We are attempting to do a reverse proxy from IPv4 to IPv6 on our end, with HAProxy, pre-opening the ports corresponding to some IPv6s. The reverse proxy sits at the dedicated server ends and redirects requests at a given port to one of the IPv6s.

However, it seems not to be working. We have multiple reports of this not working. This is (part of) our haproxy.cfg file:

maxconn 40000 # Increased to handle more connections

```
# SSL settings
tune.ssl.default-dh-param 2048
ssl-default-bind-ciphers ECDHE-ECDSA-AES128-GCM-SHA256:ECDHE-RSA-AES128-GCM-SHA256:ECDHE-ECDSA-AES256-GCM-SHA384:ECDHE-RSA-AES256-GCM-SHA384:ECDHE-ECDSA-CHACH>
ssl-default-bind-options no-sslv3 no-tlsv10 no-tlsv11 no-tls-tickets

```

defaults  
log global  
mode tcp  
option tcplog  
option dontlognull  
timeout connect 5000  
timeout client 50000  
timeout server 50000

frontend ipv4\_to\_ipv6\_frontend  
bind x.x.x.x:10000-12549 transparent  
mode tcp  
option tcplog  
use\_backend ipv6\_back

frontend http\_frontend  
bind x.x.x.x:80 transparent  
mode http  
option httplog  
use\_backend ipv6\_http\_back

frontend https\_frontend  
bind x.x.x.x:443 transparent  
mode tcp  
option tcplog  
tcp-request inspect-delay 5s  
tcp-request content accept if { req.ssl\_hello\_type 1 }  
use\_backend ipv6\_https\_back

backend ipv6\_back  
mode tcp  
balance roundrobin  
server ipv6-1-10000 [2xxx:xxx:xxx:xxxx::1]:10000 check  
server ipv6-1-10000 [2xxx:xxx:xxx:xxxx::1]:10001 check  
server ipv6-1-10000 [2xxx:xxx:xxx:xxxx::1]:10002 check  
…  
server ipv6-1-10000 [2xxx:xxx:xxx:xxxx::1]:10009 check  
server ipv6-2-10010 [2xxx:xxx:xxx:xxxy::1]:10010 check  
server ipv6-2-10010 [2xxx:xxx:xxx:xxxy::1]:10011 check  
server ipv6-2-10010 [2xxx:xxx:xxx:xxxy::1]:10012 check  
(…)

We have iptables rules to allow for these TCP ports and forward them (but not ip6tables rules).

What are we doing wrong here?  
Thank you. Sorry for the inconvenience!