shorewall-interfaces5interfacesShorewall interfaces file/etc/shorewall/interfacesDescriptionThe interfaces file serves to define the firewall's network
interfaces to Shorewall. The order of entries in this file is not
significant in determining zone composition.The columns in the file are as follows.ZONE -
zone-nameZone for this interface. Must match the name of a zone
declared in /etc/shorewall/zones. You may not list the firewall zone
in this column.If the interface serves multiple zones that will be defined in
the shorewall-hosts(5)
file, you should place "-" in this column.If there are multiple interfaces to the same zone, you must
list them in separate entries.Example:
#ZONE INTERFACE BROADCAST
loc eth1 -
loc eth2 -
INTERFACE -
interface[:port]Logical name of interface. Each interface may be listed only
once in this file. You may NOT specify the name of a "virtual"
interface (e.g., eth0:0) here; see http://www.shorewall.net/FAQ.htm#faq18.
If the option is not specified, then the
logical name is also the name of the actual interface.You may use wildcards here by specifying a prefix followed by
the plus sign ("+"). For example, if you want to make an entry that
applies to all PPP interfaces, use 'ppp+'; that would match ppp0,
ppp1, ppp2, … Please note that the '+' means 'one or more additional characters' so 'ppp'
does not match 'ppp+'.When using Shorewall versions before 4.1.4, care must be
exercised when using wildcards where there is another zone that uses
a matching specific interface. See shorewall-nesting(5) for a
discussion of this problem.Shorewall allows '+' as an interface name.There is no need to define the loopback interface (lo) in this
file.If a port is given, then the
interface must have been defined
previously with the option. The OPTIONS
column may not contain the following options when a
port is given.arp_filterarp_ignorebridgelog_martiansmssoptionalproxyarprequiredroutefiltersourcerouteupnpwaitBROADCAST (Optional) -
{-|detect|address[,address]...}If you use the special value detect, Shorewall will detect the broadcast
address(es) for you if your iptables and kernel include Address Type
Match support.If your iptables and/or kernel lack Address Type Match support
then you may list the broadcast address(es) for the network(s) 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.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.OPTIONS (Optional) -
[option[,option]...]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.arp_filter[={0|1}]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.Only those interfaces with the
option will have their setting
changed; the value assigned to the setting will be the value
specified (if any) or 1 if no value is given.This option does not work with a wild-card
interface name (e.g., eth0.+) in
the INTERFACE column.arp_ignore[=number]If specified, this interface will respond to arp
requests based on the value of number
(defaults to 1).1 - reply only if the target IP address is local address
configured on the incoming interface2 - reply only if the target IP address is local address
configured on the incoming interface and the sender's IP
address is part from same subnet on this interface's
address3 - do not reply for local addresses configured with
scope host, only resolutions for global and link4-7 - reserved8 - do not reply for all local addressesThis option does not work with a wild-card
interface name (e.g., eth0.+) in
the INTERFACE column.Do not specify arp_ignore for any interface involved
in Proxy ARP.blacklistCheck packets arriving on this interface against the
shorewall6-blacklist(5)
file.Beginning with Shorewall 4.4.13:If a zone is given in the
ZONES column, then the behavior is as if blacklist had been specified in the
IN_OPTIONS column of shorewall-zones(5).Otherwise, the option is ignored with a
warning:
WARNING: The 'blacklist'
option is ignored on mult-zone
interfaces
bridgeDesignates the interface as a bridge. Beginning with
Shorewall 4.4.7, setting this option also sets
.dhcpSpecify this option when any of the following are
true:the interface gets its IP address via DHCPthe interface is used by a DHCP server running on
the firewallthe interface has a static IP but is on a LAN
segment with lots of DHCP clients.the interface is a simple bridge with a
DHCP server on one port and DHCP clients on another
port.If you use Shorewall-perl for
firewall/bridging, then you need to include
DHCP-specific rules in shorewall-rules(8).
DHCP uses UDP ports 67 and 68.This option allows DHCP datagrams to enter and leave the
interface.logmartians[={0|1}]Turn on kernel martian logging (logging of packets with
impossible source addresses. It is strongly suggested that if
you set routefilter on an
interface that you also set logmartians. Even if you do not specify
the option, it is a good idea to
specify because your distribution
may have enabled route filtering without you knowing
it.Only those interfaces with the
option will have their setting
changed; the value assigned to the setting will be the value
specified (if any) or 1 if no value is given.To find out if route filtering is set on a given
interface, check the contents of
/proc/sys/net/ipv4/conf/interface/rp_filter
- a non-zero value indicates that route filtering is
enabled.Example: teastep@lists:~$ cat /proc/sys/net/ipv4/conf/eth0/rp_filter
1
teastep@lists:~$ This option does not work with a wild-card
interface name (e.g., eth0.+) in
the INTERFACE column.
This option may also be enabled globally in the shorewall.conf(5)
file.
maclistConnection 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.mss=numberAdded in Shorewall 4.0.3. Causes forwarded TCP SYN
packets entering or leaving on this interface to have their
MSS field set to the specified
number.nets=(net[,...])Limit the zone named in the ZONE column to only the
listed networks. The parentheses may be omitted if only a
single net is given (e.g.,
nets=192.168.1.0/24). Limited broadcast to the zone is
supported. Beginning with Shorewall 4.4.1, multicast traffic
to the zone is also supported.nets=dynamicDefines the zone as dynamic.
Requires ipset match support in your iptables and kernel. See
http://www.shorewall.net/Dynamic.html
for further information.nosmurfsFilter packets for smurfs (packets with a broadcast
address as the source).Smurfs will be optionally logged based on the setting of
SMURF_LOG_LEVEL in shorewall.conf(5). After
logging, the packets are dropped.optionalWhen is specified for an
interface, Shorewall will be silent when:a /proc/sys/net/ipv4/conf/
entry for the interface cannot be modified (including for
proxy ARP).The first address of the interface cannot be
obtained.May not be specified with required.physical=nameAdded in Shorewall 4.4.4. When specified, the interface
or port name in the INTERFACE column is a logical name that
refers to the name given in this option. It is useful when you
want to specify the same wildcard port name on two or more
bridges. See http://www.shorewall.net/bridge-Shorewall-perl.html#Multiple.If the interface name is a wildcard
name (ends with '+'), then the physical
name must also end in '+'.If is not specified, then it's
value defaults to the interface
name.proxyarp[={0|1}]Sets
/proc/sys/net/ipv4/conf/interface/proxy_arp.
Do NOT use this option if you are employing Proxy ARP through
entries in shorewall-proxyarp(5).
This option is intended solely for use with Proxy ARP
sub-networking as described at: http://tldp.org/HOWTO/Proxy-ARP-Subnet/index.html.
Note: This option does
not work with a wild-card interface
name (e.g., eth0.+) in the INTERFACE column.Only those interfaces with the
option will have their setting changed; the value assigned to
the setting will be the value specified (if any) or 1 if no
value is given.requiredAdded in Shorewall 4.4.10. If this option is set, the
firewall will fail to start if the interface is not usable.
May not be specified together with optional.routebackIf specified, indicates that Shorewall should include
rules that allow traffic arriving on this interface to be
routed back out that same interface. This option is also
required when you have used a wildcard in the INTERFACE column
if you want to allow traffic between the interfaces that match
the wildcard.Beginning with Shorewall 4.4.20, if you specify this
option, then you should also specify either
(see below) or
on all interfaces (see
below).routefilter[={0|1|2}]Turn on kernel route filtering for this interface
(anti-spoofing measure).Only those interfaces with the
option will have their setting
changes; the value assigned to the setting will be the value
specified (if any) or 1 if no value is given.The value 2 is only available with Shorewall 4.4.5.1 and
later when the kernel version is 2.6.31 or later. It specifies
a loose form of reverse path
filtering.This option does not work with a wild-card
interface name (e.g., eth0.+) in
the INTERFACE column.This option can also be enabled globally in the shorewall.conf(5)
file.There are certain cases where
cannot be used on an
interface:If USE_DEFAULT_RT=Yes in shorewall.conf(5) and
the interface is listed in shorewall-providers(5).If there is an entry for the interface in shorewall-providers(5)
that doesn't specify the
option.If IPSEC is used to allow a road-warrior to have a
local address, then any interface through which the
road-warrior might connect cannot specify
.sfilter=(net[,...])Added in Shorewall 4.4.20. This option provides an
anti-spoofing alternative to on
interfaces where that option cannot be used, but where the
option is required (on a bridge,
for example). On these interfaces,
should list those local networks that are connected to the
firewall through other interfaces.sourceroute[={0|1}]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/interface/accept_source_route
to 1). Only set this option if you know what you are doing.
This might represent a security risk and is usually
unneeded.Only those interfaces with the
option will have their setting
changed; the value assigned to the setting will be the value
specified (if any) or 1 if no value is given.This option does not work with a wild-card
interface name (e.g., eth0.+) in
the INTERFACE column.tcpflagsPackets 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.upnpIncoming requests from this interface may be remapped
via UPNP (upnpd). See http://www.shorewall.net/UPnP.html.upnpclientThis option is intended for laptop users who always run
Shorewall on their system yet need to run UPnP-enabled client
apps such as Transmission (BitTorrent client). The option
causes Shorewall to detect the default gateway through the
interface and to accept UDP packets from that gateway. Note
that, like all aspects of UPnP, this is a security hole so use
this option at your own risk.wait=secondsAdded in Shorewall 4.4.10. Causes the generated script
to wait up to seconds seconds for the
interface to become usable before applying the required or optional options.ExampleExample 1: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 its IP address via DHCP from
subnet 206.191.149.192/27. You have a DMZ with subnet 192.168.2.0/24
using eth2.Your entries for this setup would look like:#ZONE INTERFACE BROADCAST OPTIONS
net eth0 206.191.149.223 dhcp
loc eth1 192.168.1.255
dmz eth2 192.168.2.255Example 2:The same configuration without specifying broadcast addresses
is:#ZONE INTERFACE BROADCAST OPTIONS
net eth0 detect dhcp
loc eth1 detect
dmz eth2 detectExample 3:You have a simple dial-in system with no ethernet
connections.#ZONE INTERFACE BROADCAST OPTIONS
net ppp0 -Example 4 (Shorewall 4.4.9 and later):You have a bridge with no IP address and you want to allow
traffic through the bridge.#ZONE INTERFACE BROADCAST OPTIONS
- br0 - routebackFILES/etc/shorewall/interfacesSee ALSOshorewall(8), shorewall-accounting(5), shorewall-actions(5),
shorewall-blacklist(5), shorewall-hosts(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_rules(5),
shorewall-routestopped(5), shorewall-rules(5), shorewall.conf(5),
shorewall-secmarks(5), shorewall-tcclasses(5), shorewall-tcdevices(5),
shorewall-tcrules(5), shorewall-tos(5), shorewall-tunnels(5),
shorewall-zones(5)