shorewall-interfaces
5
interfaces
Shorewall interfaces file
/etc/shorewall/interfaces
Description
The interfaces file serves to define the firewall's network
interfaces to Shorewall.
The columns in the file are as follows.
ZONE —
zone-name
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.
If the interface serves multiple zones that will be defined in
the /etc/shorewall/hosts 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
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
You may specify wildcards here. For example, if you want to
make an entry that applies to all PPP interfaces, use 'ppp+'.
There is no need to define the loopback interface (lo) in this
file.
BROADCAST (Optional) —
{-|detect|address[,address]...}
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 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.
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.
dhcp
Specify this option when any of the following are
true:
the interface gets its IP address via DHCP
the interface is used by a DHCP server running on
the firewall
you have a static IP but are on a LAN segment with
lots of DHCP clients.
the interface is a bridge with a DHCP server on one
port and DHCP clients on another port.
norfc1918
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.
routefilter
Turn on kernel route filtering for this interface
(anti-spoofing measure). This option can also be enabled
globally in the shorewall.conf(5) file.
logmartians
Turn on kernel martian logging (logging of packets with
impossible source addresses. It is suggested that if you set
routefilter on an interface
that you also set logmartians. This option may also be
enabled globally in the shorewall.conf(5) file.
blacklist
Check packets arriving on this interface against the
shorewall-blacklist(5) file.
maclist
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.
tcpflags
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.
proxyarp
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://www.tldp.org/HOWTO/mini/Proxy-ARP-Subnet
routeback
If specified, indicates that Shorewall should include
rules that allow filtering traffic arriving on this interface
back out that same interface.
arp_filter
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.
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 interface
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
3 - do not reply for local addresses configured with
scope host, only resolutions for global and link
4-7 - reserved
8 - do not reply for all local addresses
Do not specify arp_ignore for any interface involved
in Proxy ARP.
nosmurfs
Filter 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.
detectnets
Automatically taylors the zone named in the ZONE column
to include only those hosts routed through the
interface.
Do not set the detectnets option on your internet
interface.
sourceroute
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 not usually
needed.
upnp
Incoming requests from this interface may be remapped
via UPNP (upnpd).
Example
Example 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 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.
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 192.168.2.255
Example 2:
The same configuration without specifying broadcast addresses
is:
#ZONE INTERFACE BROADCAST OPTIONS
net eth0 detect dhcp
loc eth1 detect
dmz eth2 detect
Example 3:
You have a simple dial-in system with no ethernet
connections.
#ZONE INTERFACE BROADCAST OPTIONS
net ppp0 -
FILES
/etc/shorewall/interfaces
See ALSO
http://www.shorewall.net/Documentation.htm#Interfaces
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)