ebtables is an application program used to set up and
maintain the tables of rules (inside the Linux kernel) that inspect Ethernet
frames. It is analogous to the iptables application, but less
complicated, due to the fact that the Ethernet protocol is much simpler than
the IP protocol.
There are two ebtables tables with built-in chains in the Linux
kernel. These tables are used to divide functionality into different sets of
rules. Each set of rules is called a chain. Each chain is an ordered list of
rules that can match Ethernet frames. If a rule matches an Ethernet frame,
then a processing specification tells what to do with that matching frame.
The processing specification is called a 'target'. However, if the frame
does not match the current rule in the chain, then the next rule in the
chain is examined and so forth. The user can create new (user-defined)
chains that can be used as the 'target' of a rule. User-defined chains are
very useful to get better performance over the linear traversal of the rules
and are also essential for structuring the filtering rules into
well-organized and maintainable sets of rules.
A firewall rule specifies criteria for an Ethernet frame and a
frame processing specification called a target. When a frame matches a rule,
then the next action performed by the kernel is specified by the target. The
target can be one of these values: ACCEPT, DROP,
CONTINUE, RETURN, an 'extension' (see below) or a jump to a
user-defined chain.
ACCEPT means to let the frame through. DROP means
the frame has to be dropped. CONTINUE means the next rule has to be
checked. This can be handy, f.e., to know how many frames pass a certain
point in the chain, to log those frames or to apply multiple targets on a
frame. RETURN means stop traversing this chain and resume at the next
rule in the previous (calling) chain. For the extension targets please refer
to the TARGET EXTENSIONS section of this man page.
As stated earlier, there are two ebtables tables in the Linux
kernel. The table names are filter and nat. Of these two
tables, the filter table is the default table that the command operates on.
If you are working with the filter table, then you can drop the '-t filter'
argument to the ebtables command. However, you will need to provide the -t
argument for nat table. Moreover, the -t argument must be the first
argument on the ebtables command line, if used.
- -t, --table
-
filter is the default table and contains three built-in chains:
INPUT (for frames destined for the bridge itself, on the level of
the MAC destination address), OUTPUT (for locally-generated or
(b)routed frames) and FORWARD (for frames being forwarded by the
bridge).
nat is mostly used to change the mac addresses and contains three
built-in chains: PREROUTING (for altering frames as soon as they
come in), OUTPUT (for altering locally generated or (b)routed
frames before they are bridged) and POSTROUTING (for altering
frames as they are about to go out). A small note on the naming of chains
PREROUTING and POSTROUTING: it would be more accurate to call them
PREFORWARDING and POSTFORWARDING, but for all those who come from the
iptables world to ebtables it is easier to have the same names. Note that
you can change the name (-E) if you don't like the
default.
After the initial ebtables '-t table' command line argument, the
remaining arguments can be divided into several groups. These groups are
commands, miscellaneous commands, rule specifications, match extensions,
watcher extensions and target extensions.
The ebtables command arguments specify the actions to perform on
the table defined with the -t argument. If you do not use the -t argument to
name a table, the commands apply to the default filter table. Only one
command may be used on the command line at a time, except when the commands
-L and -Z are combined or the commands -N and -P
are combined.
- -A, --append
- Append a rule to the end of the selected chain.
- -D, --delete
- Delete the specified rule or rules from the selected chain. There are two
ways to use this command. The first is by specifying an interval of rule
numbers to delete (directly after -D). Syntax:
start_nr[:end_nr] (use -L --Ln to list the rules with
their rule number). When end_nr is omitted, all rules starting from
start_nr are deleted. Using negative numbers is allowed, for more
details about using negative numbers, see the -I command. The
second usage is by specifying the complete rule as it would have been
specified when it was added. Only the first encountered rule that is the
same as this specified rule, in other words the matching rule with the
lowest (positive) rule number, is deleted.
- -C,
--change-counters
- Change the counters of the specified rule or rules from the selected
chain. There are two ways to use this command. The first is by specifying
an interval of rule numbers to do the changes on (directly after
-C). Syntax: start_nr[:end_nr] (use -L --Ln to
list the rules with their rule number). The details are the same as for
the -D command. The second usage is by specifying the complete rule
as it would have been specified when it was added. Only the counters of
the first encountered rule that is the same as this specified rule, in
other words the matching rule with the lowest (positive) rule number, are
changed. In the first usage, the counters are specified directly after the
interval specification, in the second usage directly after -C.
First the packet counter is specified, then the byte counter. If the
specified counters start with a '+', the counter values are added to the
respective current counter values. If the specified counters start with a
'-', the counter values are decreased from the respective current counter
values. No bounds checking is done. If the counters don't start with '+'
or '-', the current counters are changed to the specified counters.
- -I, --insert
- Insert the specified rule into the selected chain at the specified rule
number. If the rule number is not specified, the rule is added at the head
of the chain. If the current number of rules equals N, then the
specified number can be between -N and N+1. For a positive
number i, it holds that i and i-N-1 specify the same
place in the chain where the rule should be inserted. The rule number 0
specifies the place past the last rule in the chain and using this number
is therefore equivalent to using the -A command. Rule numbers
structly smaller than 0 can be useful when more than one rule needs to be
inserted in a chain.
- -P, --policy
- Set the policy for the chain to the given target. The policy can be
ACCEPT, DROP or RETURN.
- -F, --flush
- Flush the selected chain. If no chain is selected, then every chain will
be flushed. Flushing a chain does not change the policy of the chain,
however.
- -Z, --zero
- Set the counters of the selected chain to zero. If no chain is selected,
all the counters are set to zero. The -Z command can be used in
conjunction with the -L command. When both the -Z and
-L commands are used together in this way, the rule counters are
printed on the screen before they are set to zero.
- -L, --list
- List all rules in the selected chain. If no chain is selected, all chains
are listed.
The following options change the output of the -L command.
--Ln
Places the rule number in front of every rule. This option is incompatible
with the --Lx option.
--Lc
Shows the counters at the end of each rule displayed by the -L
command. Both a frame counter (pcnt) and a byte counter (bcnt) are
displayed. The frame counter shows how many frames have matched the
specific rule, the byte counter shows the sum of the frame sizes of these
matching frames. Using this option in combination with the
--Lx option causes the counters to be written out in the
'-c <pcnt> <bcnt>' option format.
--Lx
Changes the output so that it produces a set of ebtables commands that
construct the contents of the chain, when specified. If no chain is
specified, ebtables commands to construct the contents of the table are
given, including commands for creating the user-defined chains (if any).
You can use this set of commands in an ebtables boot or reload script. For
example the output could be used at system startup. The --Lx option
is incompatible with the --Ln listing option. Using the --Lx
option together with the --Lc option will cause the counters to be
written out in the '-c <pcnt> <bcnt>' option
format.
--Lmac2
Shows all MAC addresses with the same length, adding leading zeroes if
necessary. The default representation omits leading zeroes in the
addresses.
- -N, --new-chain
- Create a new user-defined chain with the given name. The number of
user-defined chains is limited only by the number of possible chain names.
A user-defined chain name has a maximum length of 31 characters. The
standard policy of the user-defined chain is ACCEPT. The policy of the new
chain can be initialized to a different standard target by using the
-P command together with the -N command. In this case, the
chain name does not have to be specified for the -P command.
- -X, --delete-chain
- Delete the specified user-defined chain. There must be no remaining
references (jumps) to the specified chain, otherwise ebtables will refuse
to delete it. If no chain is specified, all user-defined chains that
aren't referenced will be removed.
- -E, --rename-chain
- Rename the specified chain to a new name. Besides renaming a user-defined
chain, you can rename a standard chain to a name that suits your taste.
For example, if you like PREFORWARDING more than PREROUTING, then you can
use the -E command to rename the PREROUTING chain. If you do rename one of
the standard ebtables chain names, please be sure to mention this fact
should you post a question on the ebtables mailing lists. It would be wise
to use the standard name in your post. Renaming a standard ebtables chain
in this fashion has no effect on the structure or functioning of the
ebtables kernel table.
- --init-table
- Replace the current table data by the initial table data.
- -v, --verbose
- Verbose mode. For appending, insertion, deletion and replacement, this
causes detailed information on the rule or rules to be printed. -v
may be specified multiple times to possibly emit more detailed debug
statements.
- -V, --version
- Show the version of the ebtables userspace program.
- -h, --help [list of
module names]
- Give a brief description of the command syntax. Here you can also specify
names of extensions and ebtables will try to write help about those
extensions. E.g. ebtables -h snat log ip arp. Specify
list_extensions to list all extensions supported by the userspace
utility.
- -j, --jump
target
- The target of the rule. This is one of the following values:
ACCEPT, DROP, CONTINUE, RETURN, a target
extension (see TARGET EXTENSIONS) or a user-defined chain
name.
- -M, --modprobe
program
- When talking to the kernel, use this program to try to
automatically load missing kernel modules.
- --concurrent
- Use a file lock to support concurrent scripts updating the ebtables kernel
tables.
The following command line arguments make up a rule specification
(as used in the add and delete commands). A "!" option before the
specification inverts the test for that specification. Apart from these
standard rule specifications there are some other command line arguments of
interest. See both the MATCH EXTENSIONS and the WATCHER
EXTENSIONS below.
- -p, --protocol [!]
protocol
- The protocol that was responsible for creating the frame. This can be a
hexadecimal number, above 0x0600, a name (e.g. ARP ) or
LENGTH. The protocol field of the Ethernet frame can be used to
denote the length of the header (802.2/802.3 networks). When the value of
that field is below or equals 0x0600, the value equals the size of
the header and shouldn't be used as a protocol number. Instead, all frames
where the protocol field is used as the length field are assumed to be of
the same 'protocol'. The protocol name used in ebtables for these frames
is LENGTH.
The file /etc/ethertypes can be used to show readable characters
instead of hexadecimal numbers for the protocols. For example,
0x0800 will be represented by IPV4. The use of this file is
not case sensitive. See that file for more information. The flag
--proto is an alias for this option.
- -i, --in-interface [!]
name
- The interface (bridge port) via which a frame is received (this option is
useful in the INPUT, FORWARD, PREROUTING and
BROUTING chains). If the interface name ends with '+', then any
interface name that begins with this name (disregarding '+') will match.
The flag --in-if is an alias for this option.
- --logical-in
[!] name
- The (logical) bridge interface via which a frame is received (this option
is useful in the INPUT, FORWARD, PREROUTING and
BROUTING chains). If the interface name ends with '+', then any
interface name that begins with this name (disregarding '+') will
match.
- -o, --out-interface [!]
name
- The interface (bridge port) via which a frame is going to be sent (this
option is useful in the OUTPUT, FORWARD and
POSTROUTING chains). If the interface name ends with '+', then any
interface name that begins with this name (disregarding '+') will match.
The flag --out-if is an alias for this option.
- --logical-out
[!] name
- The (logical) bridge interface via which a frame is going to be sent (this
option is useful in the OUTPUT, FORWARD and
POSTROUTING chains). If the interface name ends with '+', then any
interface name that begins with this name (disregarding '+') will
match.
- -s, --source [!]
address[/mask]
- The source MAC address. Both mask and address are written as 6 hexadecimal
numbers separated by colons. Alternatively one can specify Unicast,
Multicast, Broadcast or BGA (Bridge Group Address):
Unicast=00:00:00:00:00:00/01:00:00:00:00:00,
Multicast=01:00:00:00:00:00/01:00:00:00:00:00,
Broadcast=ff:ff:ff:ff:ff:ff/ff:ff:ff:ff:ff:ff or
BGA=01:80:c2:00:00:00/ff:ff:ff:ff:ff:ff. Note that a broadcast
address will also match the multicast specification. The flag --src
is an alias for this option.
- -d, --destination [!]
address[/mask]
- The destination MAC address. See -s (above) for more details on MAC
addresses. The flag --dst is an alias for this option.
- -c, --set-counter pcnt
bcnt
- If used with -A or -I, then the packet and byte counters of
the new rule will be set to pcnt, resp. bcnt. If used with
the -C or -D commands, only rules with a packet and byte
count equal to pcnt, resp. bcnt will match.
Ebtables extensions are dynamically loaded into the userspace
tool, there is therefore no need to explicitly load them with a -m option
like is done in iptables. These extensions deal with functionality supported
by kernel modules supplemental to the core ebtables code.
Specify 802.3 DSAP/SSAP fields or SNAP type. The protocol must be
specified as LENGTH (see the option -p above).
- --802_3-sap [!] sap
- DSAP and SSAP are two one byte 802.3 fields. The bytes are always equal,
so only one byte (hexadecimal) is needed as an argument.
- --802_3-type [!] type
- If the 802.3 DSAP and SSAP values are 0xaa then the SNAP type field must
be consulted to determine the payload protocol. This is a two byte
(hexadecimal) argument. Only 802.3 frames with DSAP/SSAP 0xaa are checked
for type.
Match a MAC address or MAC/IP address pair versus a list of MAC
addresses and MAC/IP address pairs. A list entry has the following format:
xx:xx:xx:xx:xx:xx[=ip.ip.ip.ip][,]. Multiple list entries are
separated by a comma, specifying an IP address corresponding to the MAC
address is optional. Multiple MAC/IP address pairs with the same MAC address
but different IP address (and vice versa) can be specified. If the MAC
address doesn't match any entry from the list, the frame doesn't match the
rule (unless "!" was used).
- --among-dst
[!] list
- Compare the MAC destination to the given list. If the Ethernet frame has
type IPv4 or ARP, then comparison with MAC/IP destination
address pairs from the list is possible.
- --among-src
[!] list
- Compare the MAC source to the given list. If the Ethernet frame has type
IPv4 or ARP, then comparison with MAC/IP source address
pairs from the list is possible.
- --among-dst-file
[!] file
- Same as --among-dst but the list is read in from the specified
file.
- --among-src-file
[!] file
- Same as --among-src but the list is read in from the specified
file.
Specify IPv4 fields. The protocol must be specified as
IPv4.
- --ip-source
[!] address[/mask]
- The source IP address. The flag --ip-src is an alias for this
option.
- --ip-destination
[!] address[/mask]
- The destination IP address. The flag --ip-dst is an alias for this
option.
- --ip-tos [!]
tos
- The IP type of service, in hexadecimal numbers. IPv4.
- --ip-protocol
[!] protocol
- The IP protocol. The flag --ip-proto is an alias for this
option.
- --ip-source-port
[!] port1[:port2]
- The source port or port range for the IP protocols 6 (TCP), 17 (UDP), 33
(DCCP) or 132 (SCTP). The --ip-protocol option must be specified as
TCP, UDP, DCCP or SCTP. If port1 is
omitted, 0:port2 is used; if port2 is omitted but a colon is
specified, port1:65535 is used. The flag --ip-sport is an
alias for this option.
- --ip-destination-port
[!] port1[:port2]
- The destination port or port range for ip protocols 6 (TCP), 17 (UDP), 33
(DCCP) or 132 (SCTP). The --ip-protocol option must be specified as
TCP, UDP, DCCP or SCTP. If port1 is
omitted, 0:port2 is used; if port2 is omitted but a colon is
specified, port1:65535 is used. The flag --ip-dport is an
alias for this option.
Specify IPv6 fields. The protocol must be specified as
IPv6.
- --ip6-source
[!] address[/mask]
- The source IPv6 address. The flag --ip6-src is an alias for this
option.
- --ip6-destination
[!] address[/mask]
- The destination IPv6 address. The flag --ip6-dst is an alias for
this option.
- --ip6-tclass
[!] tclass
- The IPv6 traffic class, in hexadecimal numbers.
- --ip6-protocol
[!] protocol
- The IP protocol. The flag --ip6-proto is an alias for this
option.
- --ip6-source-port
[!] port1[:port2]
- The source port or port range for the IPv6 protocols 6 (TCP), 17 (UDP), 33
(DCCP) or 132 (SCTP). The --ip6-protocol option must be specified
as TCP, UDP, DCCP or SCTP. If port1 is
omitted, 0:port2 is used; if port2 is omitted but a colon is
specified, port1:65535 is used. The flag --ip6-sport is an
alias for this option.
- --ip6-destination-port
[!] port1[:port2]
- The destination port or port range for IPv6 protocols 6 (TCP), 17 (UDP),
33 (DCCP) or 132 (SCTP). The --ip6-protocol option must be
specified as TCP, UDP, DCCP or SCTP. If
port1 is omitted, 0:port2 is used; if port2 is
omitted but a colon is specified, port1:65535 is used. The flag
--ip6-dport is an alias for this option.
- --ip6-icmp-type
[!]
{type[:type]/code[:code]|typename}
- Specify ipv6-icmp type and code to match. Ranges for both type and code
are supported. Type and code are separated by a slash. Valid numbers for
type and range are 0 to 255. To match a single type including all valid
codes, symbolic names can be used instead of numbers. The list of known
type names is shown by the command
ebtables --help ip6
This option is only valid for --ip6-prococol ipv6-icmp.
This module matches at a limited rate using a token bucket filter.
A rule using this extension will match until this limit is reached. It can
be used with the --log watcher to give limited logging, for example.
Its use is the same as the limit match of iptables.
- --limit [value]
- Maximum average matching rate: specified as a number, with an optional
/second, /minute, /hour, or /day suffix; the
default is 3/hour.
- --limit-burst
[number]
- Maximum initial number of packets to match: this number gets recharged by
one every time the limit specified above is not reached, up to this
number; the default is 5.
- --mark [!] [value][/mask]
- Matches frames with the given unsigned mark value. If a value and
mask are specified, the logical AND of the mark value of the frame
and the user-specified mask is taken before comparing it with the
user-specified mark value. When only a mark value is
specified, the packet only matches when the mark value of the frame equals
the user-specified mark value. If only a mask is specified,
the logical AND of the mark value of the frame and the user-specified
mask is taken and the frame matches when the result of this logical
AND is non-zero. Only specifying a mask is useful to match multiple
mark values.
- --pkttype-type
[!] type
- Matches on the Ethernet "class" of the frame, which is
determined by the generic networking code. Possible values:
broadcast (MAC destination is the broadcast address),
multicast (MAC destination is a multicast address), host
(MAC destination is the receiving network device), or otherhost
(none of the above).
Specify stp BPDU (bridge protocol data unit) fields. The
destination address (-d) must be specified as the bridge group
address (BGA). For all options for which a range of values can
be specified, it holds that if the lower bound is omitted (but the colon is
not), then the lowest possible lower bound for that option is used, while if
the upper bound is omitted (but the colon again is not), the highest
possible upper bound for that option is used.
- --stp-type [!]
type
- The BPDU type (0-255), recognized non-numerical types are config,
denoting a configuration BPDU (=0), and tcn, denothing a topology
change notification BPDU (=128).
- --stp-flags
[!] flag
- The BPDU flag (0-255), recognized non-numerical flags are
topology-change, denoting the topology change flag (=1), and
topology-change-ack, denoting the topology change acknowledgement
flag (=128).
- --stp-root-prio
[!] [prio][:prio]
- The root priority (0-65535) range.
- --stp-root-addr
[!] [address][/mask]
- The root mac address, see the option -s for more details.
- --stp-root-cost
[!] [cost][:cost]
- The root path cost (0-4294967295) range.
- --stp-sender-prio
[!] [prio][:prio]
- The BPDU's sender priority (0-65535) range.
- --stp-sender-addr
[!] [address][/mask]
- The BPDU's sender mac address, see the option -s for more
details.
- --stp-port [!]
[port][:port]
- The port identifier (0-65535) range.
- --stp-msg-age
[!] [age][:age]
- The message age timer (0-65535) range.
- --stp-max-age
[!] [age][:age]
- The max age timer (0-65535) range.
- --stp-hello-time
[!] [time][:time]
- The hello time timer (0-65535) range.
- --stp-forward-delay
[!] [delay][:delay]
- The forward delay timer (0-65535) range.
Specify 802.1Q Tag Control Information fields. The protocol must
be specified as 802_1Q (0x8100).
- --vlan-id [!]
id
- The VLAN identifier field (VID). Decimal number from 0 to 4095.
- --vlan-prio
[!] prio
- The user priority field, a decimal number from 0 to 7. The VID should be
set to 0 ("null VID") or unspecified (in the latter case the VID
is deliberately set to 0).
- --vlan-encap
[!] type
- The encapsulated Ethernet frame type/length. Specified as a hexadecimal
number from 0x0000 to 0xFFFF or as a symbolic name from
/etc/ethertypes.
Watchers only look at frames passing by, they don't modify them
nor decide to accept the frames or not. These watchers only see the frame if
the frame matches the rule, and they see it before the target is
executed.
The log watcher writes descriptive data about a frame to the
syslog.
- --log
-
Log with the default loggin options: log-level= info,
log-prefix="", no ip logging, no arp logging.
- --log-level
level
-
Defines the logging level. For the possible values, see ebtables -h
log. The default level is info.
- --log-prefix
text
-
Defines the prefix text to be printed at the beginning of the line
with the logging information.
- --log-ip
-
Will log the ip information when a frame made by the ip protocol matches the
rule. The default is no ip information logging.
- --log-ip6
-
Will log the ipv6 information when a frame made by the ipv6 protocol matches
the rule. The default is no ipv6 information logging.
- --log-arp
-
Will log the (r)arp information when a frame made by the (r)arp protocols
matches the rule. The default is no (r)arp information logging.
The nflog watcher passes the packet to the loaded logging backend
in order to log the packet. This is usually used in combination with
nfnetlink_log as logging backend, which will multicast the packet through a
netlink socket to the specified multicast group. One or more
userspace processes may subscribe to the group to receive the packets.
- --nflog
-
Log with the default logging options
- --nflog-group
nlgroup
-
The netlink group (1 - 2^32-1) to which packets are (only applicable for
nfnetlink_log). The default value is 1.
- --nflog-prefix
prefix
-
A prefix string to include in the log message, up to 30 characters long,
useful for distinguishing messages in the logs.
- --nflog-range
size
-
The number of bytes to be copied to userspace (only applicable for
nfnetlink_log). nfnetlink_log instances may specify their own range, this
option overrides it.
- --nflog-threshold
size
-
Number of packets to queue inside the kernel before sending them to
userspace (only applicable for nfnetlink_log). Higher values result in
less overhead per packet, but increase delay until the packets reach
userspace. The default value is 1.
The ulog watcher passes the packet to a userspace logging daemon
using netlink multicast sockets. This differs from the log watcher in the
sense that the complete packet is sent to userspace instead of a descriptive
text and that netlink multicast sockets are used instead of the syslog. This
watcher enables parsing of packets with userspace programs, the physical
bridge in and out ports are also included in the netlink messages. The ulog
watcher module accepts 2 parameters when the module is loaded into the
kernel (e.g. with modprobe): nlbufsiz specifies how big the buffer
for each netlink multicast group is. If you say nlbufsiz=8192, for
example, up to eight kB of packets will get accumulated in the kernel until
they are sent to userspace. It is not possible to allocate more than 128kB.
Please also keep in mind that this buffer size is allocated for each nlgroup
you are using, so the total kernel memory usage increases by that factor.
The default is 4096. flushtimeout specifies after how many hundredths
of a second the queue should be flushed, even if it is not full yet. The
default is 10 (one tenth of a second).
- --ulog
-
Use the default settings: ulog-prefix="", ulog-nlgroup=1,
ulog-cprange=4096, ulog-qthreshold=1.
- --ulog-prefix
text
-
Defines the prefix included with the packets sent to userspace.
- --ulog-nlgroup
group
-
Defines which netlink group number to use (a number from 1 to 32). Make sure
the netlink group numbers used for the iptables ULOG target differ from
those used for the ebtables ulog watcher. The default group number is
1.
- --ulog-cprange
range
-
Defines the maximum copy range to userspace, for packets matching the rule.
The default range is 0, which means the maximum copy range is given by
nlbufsiz. A maximum copy range larger than 128*1024 is meaningless
as the packets sent to userspace have an upper size limit of
128*1024.
- --ulog-qthreshold
threshold
-
Queue at most threshold number of packets before sending them to
userspace with a netlink socket. Note that packets can be sent to
userspace before the queue is full, this happens when the ulog kernel
timer goes off (the frequency of this timer depends on
flushtimeout).
The arpreply target can be used in the PREROUTING
chain of the nat table. If this target sees an ARP request it will
automatically reply with an ARP reply. The used MAC address for the reply
can be specified. The protocol must be specified as ARP. When the ARP
message is not an ARP request or when the ARP request isn't for an IP
address on an Ethernet network, it is ignored by this target
(CONTINUE). When the ARP request is malformed, it is dropped
(DROP).
- --arpreply-mac
address
- Specifies the MAC address to reply with: the Ethernet source MAC and the
ARP payload source MAC will be filled in with this address.
- --arpreply-target
target
- Specifies the standard target. After sending the ARP reply, the rule still
has to give a standard target so ebtables knows what to do with the ARP
request. The default target is DROP.
The dnat target can only be used in the PREROUTING
and OUTPUT chains of the nat table. It specifies that the
destination MAC address has to be changed.
- --to-destination
address
-
Change the destination MAC address to the specified address. The flag
--to-dst is an alias for this option.
- --dnat-target
target
-
Specifies the standard target. After doing the dnat, the rule still has to
give a standard target so ebtables knows what to do with the dnated frame.
The default target is ACCEPT. Making it CONTINUE could let
you use multiple target extensions on the same frame. Making it
DROP only makes sense in the BROUTING chain but using the
redirect target is more logical there. RETURN is also
allowed. Note that using RETURN in a base chain is not allowed (for
obvious reasons).
The mark target can be used in every chain of every
table. It is possible to use the marking of a frame/packet in both ebtables
and iptables, if the bridge-nf code is compiled into the kernel. Both put
the marking at the same place. This allows for a form of communication
between ebtables and iptables.
- --mark-set
value
-
Mark the frame with the specified non-negative value.
- --mark-or
value
-
Or the frame with the specified non-negative value.
- --mark-and
value
-
And the frame with the specified non-negative value.
- --mark-xor
value
-
Xor the frame with the specified non-negative value.
- --mark-target
target
-
Specifies the standard target. After marking the frame, the rule still has
to give a standard target so ebtables knows what to do. The default target
is ACCEPT. Making it CONTINUE can let you do other things
with the frame in subsequent rules of the chain.
The redirect target will change the MAC target address to
that of the bridge device the frame arrived on. This target can only be used
in the PREROUTING chain of the nat table. The MAC address of
the bridge is used as destination address."
- --redirect-target
target
-
Specifies the standard target. After doing the MAC redirect, the rule still
has to give a standard target so ebtables knows what to do. The default
target is ACCEPT. Making it CONTINUE could let you use
multiple target extensions on the same frame. Making it DROP in the
BROUTING chain will let the frames be routed. RETURN is also
allowed. Note that using RETURN in a base chain is not
allowed.
The snat target can only be used in the POSTROUTING
chain of the nat table. It specifies that the source MAC address has
to be changed.
- --to-source
address
-
Changes the source MAC address to the specified address. The flag
--to-src is an alias for this option.
- --snat-target
target
-
Specifies the standard target. After doing the snat, the rule still has to
give a standard target so ebtables knows what to do. The default
target is ACCEPT. Making it CONTINUE could let you use
multiple target extensions on the same frame. Making it DROP
doesn't make sense, but you could do that too. RETURN is
also allowed. Note that using RETURN in a base chain is not
allowed.
- --snat-arp
-
Also change the hardware source address inside the arp header if the packet
is an arp message and the hardware address length in the arp header is 6
bytes.