Edit I have thought that excessive number of "deny" lines are confusing apache into blocking unlisted IPv4 addresses. But comment of @Ladadadada made me pinpoint the exact issue. You can read my old question below. The problem is, the following line:
deny from 126.96.36.199/19
blocks the IPv6 addresses
How is this possible?
I have a really long list of blocked IP addresses, activated by an
Include directive inside the
This file only contains IPv4 addresses, but my server is also blocking a limited number of IPv6 addresses. It's not blocking all IPv6 traffic. If I remove the blocks, those IPv6 addresses can access the server just fine.
Originally the block file had each IP block on a separate "deny from" line. I tried combining every 40 of them to reduce the rule count and file size. It still did not help. But when I truncated the rules to 4-5 deny lines, it worked as expected and did not block the IPv6 addresses.
These are sample logs from access log.
2a01:4f8:120:8201::2 - - [03/Mar/2013:15:01:07 +0200] "GET /tdf/ HTTP/1.1" 403 387 "-" "MirrorBrain Probe (see http://mirrorbrain.org/probe_info)"
and from error log
[Sun Mar 03 15:01:07 2013] [error] [client 2a01:4f8:120:8201::2] client denied by server configuration: /mirror/pub/tdf/
How can I list a large number of "deny" directives ? I cannot control the firewall of the machine, so it's out of the question.