7
IPsec VPN
141
2. The
CA
server
is
a
private
server
with
tunnels
set
up
over
the
public
Internet
and
with
clients
that
will
try
to
validate
the
certificate
received
from
the
SEG.
In
this
case,
the
following
must
be
done:
a. A
private
DNS
server
must
be
configured
so
that
the
SEG
can
locate
the
private
CA
server
to
validate
the
certificates
coming
from
clients.
b. The
external
IP
address
of
the
SEG
needs
to
be
registered
in
the
public
DNS
system
so
that
the
FQDN
reference
to
the
private
CA
server
in
certificates
sent
to
clients
can
be
resolved.
For
example,
the
SEG
may
send
a
certificate
to
a
client
with
an
FQDN
of
ca.company.com.
This
will
need
to
be
resolvable
by
the
client
to
a
public
external
IP
address
of
the
SEG
through
the
public
DNS
system.
The
same
steps
should
be
followed
if
the
other
side
of
the
tunnel
is
another
security
gateway
instead
of
being
many
clients.
3. The
CA
server
is
a
commercial
server
on
the
public
Internet.
In
this,
the
simplest
case,
public
DNS
servers
will
resolve
the
FQDN.
The
only
requirement
is
that
the
SEG
will
need
to
have
at
least
one
public
DNS
server
address
configured
to
resolve
the
FQDNs
in
the
certificates
it
receives.
•
It
must
be
also
possible
for
a
server
request
to
pass
from
the
validation
request
source
(either
the
SEG
or
a
client)
to
the
CA
server
and
the
reply
to
be
received.
If
the
request
is
going
to
pass
through
the
SEG,
the
appropriate
rules
in
the
SEG
IP
rule
set
need
to
be
defined
to
allow
this
traffic
through.
The
Service
object
used
in
the
IP
rules
should
be
chosen
to
match
the
protocols
that
may
be
used
for
the
request.
IP
rules
are
not
required
if
the
SEG
itself
is
issuing
the
request
to
the
CA
server.
Actions
taken
by
the
SEG
are
trusted
by
default.
This
is
the
case
when
the
SEG
must
validate
certificates
in
an
LTE
telecom
scenario
and
is
a
general
rule
that
also
applies
to
DNS
resolution
requests
issued
by
the
SEG.
•
If
LDAP
requests
are
going
to
be
sent
to
a
CA
server,
the
server
must
be
configured
to
accept
anonymous
LDAP
requests.
Microsoft
documentation
may
refer
to
this
as
Anonymous
LDAP
Binding
.
For
example,
the
default
setting
for
some
Windows
Active
Directory
servers
is
to
reject
anonymous
LDAP
requests,
so
this
must
be
changed.
The
SEG
always
queries
LDAP
servers
with
anonymous
requests.
If
the
server
is
not
configured
to
accept
them,
authentication
will
fail.