Provided by: shorewall-common_4.2.10-1_all bug

NAME

       interfaces - Shorewall interfaces file

SYNOPSIS

       /etc/shorewall/interfaces

DESCRIPTION

       The 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-name
           Zone 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[1](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]
           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

           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, ...

           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[2](5) for a
           discussion of this problem.

           Beginning with Shorewall 4.2.3, Shorewall-perl allows ´+´ as an
           interface name.

           There is no need to define the loopback interface (lo) in this
           file.

           (Shorewall-perl only) If a port is given, then the interface must
           have been defined previously with the bridge option. The OPTIONS
           column may not contain the following options when a port is given.

               arp_filter

               arp_ignore

               bridge

               log_martians

               mss

               optional

               proxyarp

               routefilter

               sourceroute

               upnp

       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.

           Note to Shorewall-perl users: Shorewall-perl only supports detect
           or - in this column. If you specify addresses, a compilation
           warning will be issued.

       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.

               The option value (0 or 1) may only be specified if you are
               using Shorewall-perl. With Shorewall-perl, only those
               interfaces with the arp_filter 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.

               Note
               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 interface

               2 - 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

               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

               Note
               This option does not work with a wild-card interface name
               (e.g., eth0.+) in the INTERFACE column.

               Warning
               Do not specify arp_ignore for any interface involved in Proxy
               ARP[3].

           blacklist
               Check packets arriving on this interface against the
               shorewall-blacklist[4](5) file.

           bridge
               (Shorewall-perl only) Designates the interface as a bridge.

           detectnets (Deprecated and not supported by Shorewall-perl)
               Automatically tailors the zone named in the ZONE column to
               include only those hosts routed through the interface.

               Warning
               Do not set the detectnets option on your internet interface.

               Support for this option will be removed in a future release of
               Shorewall-perl. Better to use the routefilter option together
               with the logmartians option.

           dhcp
               Specify this option when any of the following are true:

                1.  the interface gets its IP address via DHCP

                2.  the interface is used by a DHCP server running on the
                   firewall

                3.  the interface has a static IP but is on a LAN segment with
                   lots of DHCP clients.

                4.  the interface is a simple bridge[5] with a DHCP server on
                   one port and DHCP clients on another port.

                   Note
                   If you use Shorewall-perl for firewall/bridging[6], then
                   you need to include DHCP-specific rules in
                   shorewall-rules[7](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 routefilter option,
               it is a good idea to specify logmartians because your
               distribution may be enabling route filtering without you
               knowing it.

               The option value (0 or 1) may only be specified if you are
               using Shorewall-perl. With Shorewall-perl, only those
               interfaces with the logmartians 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.

               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:~$

               Note
               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[8](5) file.

           maclist
               Connection requests from this interface are compared against
               the contents of shorewall-maclist[9](5). If this option is
               specified, the interface must be an ethernet NIC and must be up
               before Shorewall is started.

           mss=number
               Added 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.

           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.

           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[8](5). After logging, the
               packets are dropped.

           optional
               Only supported by Shorewall-perl. When optional 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.

                    I specify optional on interfaces to Xen virtual machines
                   that may or may not be running when Shorewall is
                   [re]started.

                   Caution
                   Use optional at your own risk. If you [re]start Shorewall
                   when an ´optional´ interface is not available and then do a
                   shorewall save, subsequent shorewall restore and shorewall
                   -f start operations will instantiate a ruleset that does
                   not support that interface, even if it is available at the
                   time of the restore/start.

           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[10](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. [11]

               Note: This option does not work with a wild-card interface name
               (e.g., eth0.+) in the INTERFACE column.

               The option value (0 or 1) may only be specified if you are
               using Shorewall-perl. With Shorewall-perl, only those
               interfaces with the proxyarp 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.

           routeback
               If 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.

           routefilter[={0|1}]
               Turn on kernel route filtering for this interface
               (anti-spoofing measure).

               The option value (0 or 1) may only be specified if you are
               using Shorewall-perl. With Shorewall-perl, only those
               interfaces with the routefilter 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.

               Note
               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[8](5) file.

           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 not usually needed.

               The option value (0 or 1) may only be specified if you are
               using Shorewall-perl. With Shorewall-perl, only those
               interfaces with the sourceroute 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.

               Note
               This option does not work with a wild-card interface name
               (e.g., eth0.+) in the INTERFACE column.

           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.

           upnp
               Incoming requests from this interface may be remapped via UPNP
               (upnpd). See http://www.shorewall.net/UPnP.html[12].

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

       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_rules(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)

NOTES

        1. shorewall-hosts
           shorewall-hosts.html

        2. shorewall-nesting
           shorewall-nesting.html

        3. Proxy ARP
           ../ProxyARP.htm

        4. shorewall-blacklist
           shorewall-blacklist.html

        5. simple bridge
           ../SimpleBridge.html

        6. Shorewall-perl for firewall/bridging
           ../bridge-Shorewall-perl.html

        7. shorewall-rules
           shorewall-rules.html

        8. shorewall.conf
           shorewall.conf.html

        9. shorewall-maclist
           shorewall-maclist.html

       10. shorewall-proxyarp
           shorewall-proxyarp.html

       11. http://tldp.org/HOWTO/Proxy-ARP-Subnet/index.html.
           http://tldp.org/HOWTO/Proxy-ARP-Subnet/index.html

       12. http://www.shorewall.net/UPnP.html
           ../UPnP.html

                                  06/18/2009            SHOREWALL-INTERFACE(5)