IP6tables and sendmail

[Deron Meranda]

On Fri, 26 Nov 2004 13:43:28 -0600, Gregory P. Ennis <pomec at pomec.net> wrote:
> In trying to tinker with iptables, hosts.allow, and the hosts.deny files on both
> systems I have not been able to make any headway.  When I used ifconfig on the FC3
> unit I noticed th6 and IP4 protocols.
>            inet addr:10.0.0.131  Bcast:10.0.0.255  Mask:255.255.255.0
>            inet6 addr: fe80::211:5bff:fe55:752c/64 Scope:Link

There should be no reason to mess with hosts.allow and hosts.deny.

The IPv6 address is normal.  The fe80... address is a dynamically
assigned IPv6 address.
RH8.0 can also do IPv6, but you have to enable it as it is not by
default in that release.  Just put "NETWORKING_IPV6=yes" in your
"/etc/sysconfig/network" configuation file.

BTW, the new prefered way of quering interfaces is with the ip(8)
command, as ifconfig is slowly being deprecated.

  ip addr show

>  Are there conflicts in using both ip4 and ip6 protocols?

No, IPv4 and IPv6 can happily coexist.  Usually the only weirdness you
may see is with DNS, as it will try to lookup IPv6 addresses first,
and then fall back to looking up IPv4.  This can sometimes cause
delays if the address has no IPv6 information.  This delay is usually
witnessed in applications like Mozilla.  But it's not a failure of any
kind and won't affect sendmail.

For sendmail to be able to talk both IPv4 and IPv6 your sendmail.mc
file will need the following two lines in it:
DAEMON_OPTIONS(`Name=MTA-v4, Family=inet')
DAEMON_OPTIONS(`Name=MTA-v6, Family=inet6')

Whenever you edit your sendmail.mc file, it's best to compile the
sendmail.cf file from it immediately afterwards:

  cd /etc/mail
  make

If you're not intentionally using IPv6 (or have not set up DNS with
IPv6 entries), you may be best to just comment out (with "dnl") or
remove the MTA-v6 option.

One thing you can try is to run sendmail directly with debugging
turned on.  Perhaps something like,

   sendmail -v -d8.1 -d0.20 recipient at your.host.com

-- 
Deron Meranda