shorewall_code/manpages/shorewall-interfaces.xml
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2006-11-15 20:04:33 +00:00

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<?xml version="1.0" encoding="UTF-8"?>
<refentry>
<refmeta>
<refentrytitle>shorewall-interfaces</refentrytitle>
<manvolnum>5</manvolnum>
</refmeta>
<refnamediv>
<refname>interfaces</refname>
<refpurpose>Shorewall interfaces file</refpurpose>
</refnamediv>
<refsynopsisdiv>
<cmdsynopsis>
<command>/etc/shorewall/interfaces</command>
</cmdsynopsis>
</refsynopsisdiv>
<refsect1>
<title>Description</title>
<para>The interfaces file serves to define the firewall's network
interfaces to Shorewall.</para>
<para>The columns in the file are as follows.</para>
<variablelist>
<varlistentry>
<term><emphasis role="bold">ZONE</emphasis></term>
<listitem>
<para>Zone for this interface. Must match the name of a zone defined
in /etc/shorewall/zones. You may not list the firewall zone in this
column.</para>
<para>If the interface serves multiple zones that will be defined in
the /etc/shorewall/hosts file, you should place "-" in this
column.</para>
<para>If there are multiple interfaces to the same zone, you must
list them in separate entries.</para>
<para>Example:</para>
<blockquote>
<programlisting>#ZONE INTERFACE BROADCAST
loc eth1 -
loc eth2 -</programlisting>
</blockquote>
</listitem>
</varlistentry>
<varlistentry>
<term><emphasis role="bold">INTERFACE</emphasis></term>
<listitem>
<para>Name of interface. Each interface may be listed only once in
this file. You may NOT specify the name of an alias (e.g., eth0:0)
here; see http://www.shorewall.net/FAQ.htm#faq18</para>
<para>You may specify wildcards here. For example, if you want to
make an entry that applies to all PPP interfaces, use 'ppp+'.</para>
<para>There is no need to define the loopback interface (lo) in this
file.</para>
</listitem>
</varlistentry>
<varlistentry>
<term><emphasis role="bold">BROADCAST</emphasis> (Optional)</term>
<listitem>
<para>The broadcast address for the subnetwork to which the
interface belongs. For P-T-P interfaces, this column is left
blank.If the interface has multiple addresses on multiple subnets
then list the broadcast addresses as a comma-separated list.</para>
<para>If you use the special value "detect", Shorewall will detect
the broadcast address(es) for you. If you select this option, the
interface must be up before the firewall is started.</para>
<para>If you don't want to give a value for this column but you want
to enter a value in the OPTIONS column, enter "-" in this
column.</para>
</listitem>
</varlistentry>
<varlistentry>
<term><emphasis role="bold">OPTIONS</emphasis> (Optional)</term>
<listitem>
<para>A comma-separated list of options from the following list. The
order in which you list the options is not significant but the list
should have no embedded white space.</para>
<variablelist>
<varlistentry>
<term><emphasis role="bold">dhcp</emphasis></term>
<listitem>
<para>Specify this option when any of the following are
true:</para>
<orderedlist spacing="compact">
<listitem>
<para>the interface gets its IP address via DHCP</para>
</listitem>
<listitem>
<para>the interface is used by a DHCP server running on
the firewall</para>
</listitem>
<listitem>
<para>you have a static IP but are on a LAN segment with
lots of DHCP clients.</para>
</listitem>
<listitem>
<para>the interface is a bridge with a DHCP server on one
port and DHCP clients on another port.</para>
</listitem>
</orderedlist>
</listitem>
</varlistentry>
<varlistentry>
<term><emphasis role="bold">norfc1918</emphasis></term>
<listitem>
<para>This interface should not receive any packets whose
source is in one of the ranges reserved by RFC 1918 (i.e.,
private or "non-routable" addresses). If packet mangling or
connection-tracking match is enabled in your kernel, packets
whose destination addresses are reserved by RFC 1918 are also
rejected.</para>
</listitem>
</varlistentry>
<varlistentry>
<term><emphasis role="bold">routefilter</emphasis></term>
<listitem>
<para>Turn on kernel route filtering for this interface
(anti-spoofing measure). This option can also be enabled
globally in the shorewall.conf(5) file.</para>
</listitem>
</varlistentry>
<varlistentry>
<term><emphasis role="bold">logmartians</emphasis></term>
<listitem>
<para>Turn on kernel martian logging (logging of packets with
impossible source addresses. It is suggested that if you set
<emphasis role="bold">routefilter</emphasis> on an interface
that you also set <emphasis
role="bold">logmartians</emphasis>. This option may also be
enabled globally in the shorewall.conf(5) file.</para>
</listitem>
</varlistentry>
<varlistentry>
<term><emphasis role="bold">blacklist</emphasis></term>
<listitem>
<para>Check packets arriving on this interface against the
shorewall-blacklist(5) file.</para>
</listitem>
</varlistentry>
<varlistentry>
<term><emphasis role="bold">maclist</emphasis></term>
<listitem>
<para>Connection requests from this interface are compared
against the contents of shorewall-maclist(5). If this option
is specified, the interface must be an ethernet NIC and must
be up before Shorewall is started.</para>
</listitem>
</varlistentry>
<varlistentry>
<term><emphasis role="bold">tcpflags</emphasis></term>
<listitem>
<para>Packets arriving on this interface are checked for
certain illegal combinations of TCP flags. Packets found to
have such a combination of flags are handled according to the
setting of TCP_FLAGS_DISPOSITION after having been logged
according to the setting of TCP_FLAGS_LOG_LEVEL.</para>
</listitem>
</varlistentry>
<varlistentry>
<term><emphasis role="bold">proxyarp</emphasis></term>
<listitem>
<para>Sets
/proc/sys/net/ipv4/conf/<emphasis>interface</emphasis>/proxy_arp.
Do NOT use this option if you are employing Proxy ARP through
entries in shorewall-proxyarp(5). This option is intended
soley for use with Proxy ARP sub-networking as described at:
http://www.tldp.org/HOWTO/mini/Proxy-ARP-Subnet</para>
</listitem>
</varlistentry>
<varlistentry>
<term><emphasis role="bold">routeback</emphasis></term>
<listitem>
<para>If specified, indicates that Shorewall should include
rules that allow filtering traffic arriving on this interface
back out that same interface.</para>
</listitem>
</varlistentry>
<varlistentry>
<term><emphasis role="bold">arp_filter</emphasis></term>
<listitem>
<para>If specified, this interface will only respond to ARP
who-has requests for IP addresses configured on the interface.
If not specified, the interface can respond to ARP who-has
requests for IP addresses on any of the firewall's interface.
The interface must be up when Shorewall is started.</para>
</listitem>
</varlistentry>
<varlistentry>
<term><emphasis
role="bold">arp_ignore</emphasis>[=<emphasis>number</emphasis>]</term>
<listitem>
<para>If specified, this interface will respond to arp
requests based on the value of <emphasis>number</emphasis>
(defaults to 1).</para>
<para>1 - reply only if the target IP address is local address
configured on the incoming interface</para>
<para>2 - reply only if the target IP address is local address
configured on the incoming interface and both with the
sender's IP address are part from same subnet on this
interface</para>
<para>3 - do not reply for local addresses configured with
scope host, only resolutions for global and link </para>
<para>4-7 - reserved</para>
<para>8 - do not reply for all local addresses</para>
<warning>
<para>Do not specify <emphasis
role="bold">arp_ignore</emphasis> for any interface involved
in Proxy ARP.</para>
</warning>
</listitem>
</varlistentry>
<varlistentry>
<term><emphasis role="bold">nosmurfs</emphasis></term>
<listitem>
<para>Filter packets for smurfs (packets with a broadcast
address as the source).</para>
<para>Smurfs will be optionally logged based on the setting of
SMURF_LOG_LEVEL in shorewall.conf(5). After logging, the
packets are dropped.</para>
</listitem>
</varlistentry>
<varlistentry>
<term><emphasis role="bold">detectnets</emphasis></term>
<listitem>
<para>Automatically taylors the zone named in the ZONE column
to include only those hosts routed through the
interface.</para>
<warning>
<para>Do not set the <emphasis
role="bold">detectnets</emphasis> option on your internet
interface.</para>
</warning>
</listitem>
</varlistentry>
<varlistentry>
<term><emphasis role="bold">sourceroute</emphasis></term>
<listitem>
<para>If this option is not specified for an interface, then
source-routed packets will not be accepted from that interface
(sets
/proc/sys/net/ipv4/conf/<emphasis>interface</emphasis>/accept_source_route
to 1). Only set this option if you know what you are you
doing. This might represent a security risk and is not usually
needed.</para>
</listitem>
</varlistentry>
<varlistentry>
<term><emphasis role="bold">upnp</emphasis></term>
<listitem>
<para>Incoming requests from this interface may be remapped
via UPNP (upnpd).</para>
</listitem>
</varlistentry>
</variablelist>
</listitem>
</varlistentry>
</variablelist>
</refsect1>
<refsect1>
<title>Example</title>
<variablelist>
<varlistentry>
<term>Example 1:</term>
<listitem>
<para> Suppose you have eth0 connected to a DSL modem and eth1
connected to your local network and that your local subnet is
192.168.1.0/24. The interface gets it's IP address via DHCP from
subnet 206.191.149.192/27. You have a DMZ with subnet 192.168.2.0/24
using eth2.</para>
<para>Your entries for this setup would look like:</para>
<programlisting>#ZONE INTERFACE BROADCAST OPTIONS
net eth0 206.191.149.223 dhcp
loc eth1 192.168.1.255
dmz eth2 192.168.2.255</programlisting>
</listitem>
</varlistentry>
<varlistentry>
<term>Example 2:</term>
<listitem>
<para>The same configuration without specifying broadcast addresses
is:</para>
<programlisting>#ZONE INTERFACE BROADCAST OPTIONS
net eth0 detect dhcp
loc eth1 detect
dmz eth2 detect</programlisting>
</listitem>
</varlistentry>
<varlistentry>
<term>Example 3:</term>
<listitem>
<para>You have a simple dial-in system with no ethernet
connections.</para>
<programlisting>#ZONE INTERFACE BROADCAST OPTIONS
net ppp0 -</programlisting>
</listitem>
</varlistentry>
</variablelist>
</refsect1>
<refsect1>
<title>FILES</title>
<para>/etc/shorewall/interfaces</para>
</refsect1>
<refsect1>
<title>See ALSO</title>
<para>shorewall(8), shorewall-accounting(5), shorewall-actions(5),
shorewall-blacklist(5), shorewall-hosts(5), shorewall-ipsec(5),
shorewall-maclist(5), shorewall-masq(5), shorewall-nat(5),
shorewall-netmap(5), shorewall-params(5), shorewall-policy(5),
shorewall-providers(5), shorewall-proxyarp(5), shorewall-route_routes(5),
shorewall-routestopped(5), shorewall-rules(5), shorewall.conf(5),
shorewall-tcclasses(5), shorewall-tcdevices(5), shorewall-tcrules(5),
shorewall-tos(5), shorewall-tunnels(5), shorewall-zones(5)</para>
</refsect1>
</refentry>