IPSET(8)IPSET(8)NAMEipset — administration tool for IP sets
SYNOPSISipset [ OPTIONS ] COMMAND [ COMMAND-OPTIONS ]
COMMANDS := { create | add | del | test | destroy | list | save |
restore | flush | rename | swap | help | version | - }
OPTIONS := { -exist | -output { plain | save | xml } | -quiet |
-resolve | -sorted | -name | -terse }
ipset create SETNAME TYPENAME [ CREATE-OPTIONS ]
ipset add SETNAME ADD-ENTRY [ ADD-OPTIONS ]
ipset del SETNAME DEL-ENTRY [ DEL-OPTIONS ]
ipset test SETNAME TEST-ENTRY [ TEST-OPTIONS ]
ipset destroy [ SETNAME ]
ipset list [ SETNAME ]
ipset save [ SETNAME ]
ipset restore
ipset flush [ SETNAME ]
ipset rename SETNAME-FROM SETNAME-TO
ipset swap SETNAME-FROM SETNAME-TO
ipset help [ TYPENAME ]
ipset version
ipset-
DESCRIPTIONipset is used to set up, maintain and inspect so called IP sets in the
Linux kernel. Depending on the type of the set, an IP set may store
IP(v4/v6) addresses, (TCP/UDP) port numbers, IP and MAC address pairs,
IP address and port number pairs, etc. See the set type definitions
below.
Iptables matches and targets referring to sets create references, which
protect the given sets in the kernel. A set cannot be destroyed while
there is a single reference pointing to it.
OPTIONS
The options that are recognized by ipset can be divided into several
different groups.
COMMANDS
These options specify the desired action to perform. Only one of them
can be specified on the command line unless otherwise specified below.
For all the long versions of the command names, you need to use only
enough letters to ensure that ipset can differentiate it from all other
commands. The ipset parser follows the order here when looking for the
shortest match in the long command names.
n, create SETNAME TYPENAME [ CREATE-OPTIONS ]
Create a set identified with setname and specified type. The
type may require type specific options. If the -exist option is
specified, ipset ignores the error otherwise raised when the
same set (setname and create parameters are identical) already
exists.
add SETNAME ADD-ENTRY [ ADD-OPTIONS ]
Add a given entry to the set. If the -exist option is specified,
ipset ignores if the entry already added to the set.
del SETNAME DEL-ENTRY [ DEL-OPTIONS ]
Delete an entry from a set. If the -exist option is specified,
ipset ignores if the entry does not added to (already expired
from) the set.
test SETNAME TEST-ENTRY [ TEST-OPTIONS ]
Test wether an entry is in a set or not. Exit status number is
zero if the tested entry is in the set and nonzero if it is
missing from the set.
x, destroy [ SETNAME ]
Destroy the specified set or all the sets if none is given.
If the set has got reference(s), nothing is done and no set
destroyed.
list [ SETNAME ] [ OPTIONS ]
List the header data and the entries for the specified set, or
for all sets if none is given. The -resolve option can be used
to force name lookups (which may be slow). When the -sorted
option is given, the entries are listed sorted (if the given set
type supports the operation). The option -output can be used to
control the format of the listing: plain, save or xml. (The
default is plain.) If the option -name is specified, just the
names of the existing sets are listed. If the option -terse is
specified, just the set names and headers are listed.
save [ SETNAME ]
Save the given set, or all sets if none is given to stdout in a
format that restore can read.
restore
Restore a saved session generated by save. The saved session
can be fed from stdin.
flush [ SETNAME ]
Flush all entries from the specified set or flush all sets if
none is given.
e, rename SETNAME-FROM SETNAME-TO
Rename a set. Set identified by SETNAME-TO must not exist.
w, swap SETNAME-FROM SETNAME-TO
Swap the content of two sets, or in another words, exchange the
name of two sets. The referred sets must exist and identical
type of sets can be swapped only.
help [ TYPENAME ]
Print help and set type specific help if TYPENAME is specified.
version
Print program version.
- If a dash is specified as command, then ipset enters a simple
interactive mode and the commands are read from the standard
input. The interactive mode can be finished by entering the
pseudo-command quit.
OTHER OPTIONS
The following additional options can be specified. The long option
names cannot be abbreviated.
-!, -exist
Ignore errors when the exactly the same set is to be created or
already added entry is added or missing entry is deleted.
-o, -output { plain | save | xml }
Select the output format to the list command.
-q, -quiet
Suppress any output to stdout and stderr. ipset will still exit
with error if it cannot continue.
-r, -resolve
When listing sets, enforce name lookup. The program will try to
display the IP entries resolved to host names which requires
slow DNS lookups.
-s, -sorted
Sorted output. When listing sets entries are listed sorted. Not
supported yet.
-n, -name
List just the names of the existing sets, i.e. suppress listing
of set headers and members.
-t, -terse
List the set names and headers, i.e. suppress listing of set
members.
SET TYPES
A set type comprises of the storage method by which the data is stored
and the data type(s) which are stored in the set. Therefore the TYPE‐
NAME parameter of the create command follows the syntax
TYPENAME := method:datatype[,datatype[,datatype]]
where the current list of the methods are bitmap, hash, and list and
the possible data types are ip, net, mac, port and iface. The dimen‐
sion of a set is equal to the number of data types in its type name.
When adding, deleting or testing entries in a set, the same comma sepa‐
rated data syntax must be used for the entry parameter of the commands,
i.e
ipset add foo ipaddr,portnum,ipaddr
The bitmap and list types use a fixed sized storage. The hash types use
a hash to store the elements. In order to avoid clashes in the hash, a
limited number of chaining, and if that is exhausted, the doubling of
the hash size is performed when adding entries by the ipset command.
When entries added by the SET target of iptables/ip6tables, then the
hash size is fixed and the set won't be duplicated, even if the new
entry cannot be added to the set.
All set types support the optional
timeout value
parameter when creating a set and adding entries. The value of the
timeout parameter for the create command means the default timeout
value (in seconds) for new entries. If a set is created with timeout
support, then the same timeout option can be used to specify
non-default timeout values when adding entries. Zero timeout value
means the entry is added permanent to the set. The timeout value of
already added elements can be changed by readding the element using the
-exist option.
If host names or service names with dash in the name are used instead
of IP addresses or service numbers, then the host name or service name
must be enclosed in square brackets. Example:
ipset add foo [test-hostname],[ftp-data]
bitmap:ip
The bitmap:ip set type uses a memory range to store either IPv4 host
(default) or IPv4 network addresses. A bitmap:ip type of set can store
up to 65536 entries.
CREATE-OPTIONS := range fromip-toip|ip/cidr [ netmask cidr ] [ timeout
value ]
ADD-ENTRY := { ip | fromip-toip | ip/cidr }
ADD-OPTIONS := [ timeout value ]
DEL-ENTRY := { ip | fromip-toip | ip/cidr }
TEST-ENTRY := ip
Mandatory create options:
range fromip-toip|ip/cidr
Create the set from the specified inclusive address range
expressed in an IPv4 address range or network. The size of the
range (in entries) cannot exceed the limit of maximum 65536 ele‐
ments.
Optional create options:
netmask cidr
When the optional netmask parameter specified, network addresses
will be stored in the set instead of IP host addresses. The cidr
prefix value must be between 1-32. An IP address will be in the
set if the network address, which is resulted by masking the
address with the specified netmask calculated from the prefix,
can be found in the set.
The bitmap:ip type supports adding or deleting multiple entries in one
command.
Examples:
ipset create foo bitmap:ip range 192.168.0.0/16
ipset add foo 192.168.1/24
ipset test foo 192.168.1.1
bitmap:ip,mac
The bitmap:ip,mac set type uses a memory range to store IPv4 and a MAC
address pairs. A bitmap:ip,mac type of set can store up to 65536
entries.
CREATE-OPTIONS := range fromip-toip|ip/cidr [ timeout value ]
ADD-ENTRY := ip[,macaddr]
ADD-OPTIONS := [ timeout value ]
DEL-ENTRY := ip[,macaddr]
TEST-ENTRY := ip[,macaddr]
Mandatory options to use when creating a bitmap:ip,mac type of set:
range fromip-toip|ip/cidr
Create the set from the specified inclusive address range
expressed in an IPv4 address range or network. The size of the
range cannot exceed the limit of maximum 65536 entries.
The bitmap:ip,mac type is exceptional in the sense that the MAC part
can be left out when adding/deleting/testing entries in the set. If we
add an entry without the MAC address specified, then when the first
time the entry is matched by the kernel, it will automatically fill out
the missing MAC address with the source MAC address from the packet. If
the entry was specified with a timeout value, the timer starts off when
the IP and MAC address pair is complete.
The bitmap:ip,mac type of sets require two src/dst parameters of the
set match and SET target netfilter kernel modules and the second one
must be src to match, add or delete entries because the set match and
SET target have access to the source MAC address only.
Examples:
ipset create foo bitmap:ip,mac range 192.168.0.0/16
ipset add foo 192.168.1.1,12:34:56:78:9A:BC
ipset test foo 192.168.1.1
bitmap:port
The bitmap:port set type uses a memory range to store port numbers and
such a set can store up to 65536 ports.
CREATE-OPTIONS := range fromport-toport [ timeout value ]
ADD-ENTRY := { port | fromport-toport }
ADD-OPTIONS := [ timeout value ]
DEL-ENTRY := { port | fromport-toport }
TEST-ENTRY := port
Mandatory options to use when creating a bitmap:port type of set:
range fromport-toport
Create the set from the specified inclusive port range.
The set match and SET target netfilter kernel modules interpret the
stored numbers as TCP or UDP port numbers.
Examples:
ipset create foo bitmap:port range 0-1024
ipset add foo 80
ipset test foo 80
hash:ip
The hash:ip set type uses a hash to store IP host addresses (default)
or network addresses. Zero valued IP address cannot be stored in a
hash:ip type of set.
CREATE-OPTIONS := [ family { inet | inet6 } ] | [ hashsize value ] [
maxelem value ] [ netmask cidr ] [ timeout value ]
ADD-ENTRY := ipaddr
ADD-OPTIONS := [ timeout value ]
DEL-ENTRY := ipaddr
TEST-ENTRY := ipaddr
Optional create options:
family { inet | inet6 }
The protocol family of the IP addresses to be stored in the set.
The default is inet, i.e IPv4.
hashsize value
The initial hash size for the set, default is 1024. The hash
size must be a power of two, the kernel automatically rounds up
non power of two hash sizes to the first correct value.
maxelem value
The maximal number of elements which can be stored in the set,
default 65536.
netmask cidr
When the optional netmask parameter specified, network addresses
will be stored in the set instead of IP host addresses. The cidr
prefix value must be between 1-32 for IPv4 and between 1-128 for
IPv6. An IP address will be in the set if the network address,
which is resulted by masking the address with the netmask calcu‐
lated from the prefix, can be found in the set.
For the inet family one can add or delete multiple entries by specify‐
ing a range or a network:
ipaddr := { ip | fromaddr-toaddr | ip/cidr }
Examples:
ipset create foo hash:ip netmask 30
ipset add foo 192.168.1.0/24
ipset test foo 192.168.1.2
hash:net
The hash:net set type uses a hash to store different sized IP network
addresses. Network address with zero prefix size cannot be stored in
this type of sets.
CREATE-OPTIONS := [ family { inet | inet6 } ] | [ hashsize value ] [
maxelem value ] [ timeout value ]
ADD-ENTRY := netaddr
ADD-OPTIONS := [ timeout value ]
DEL-ENTRY := netaddr
TEST-ENTRY := netaddr
where netaddr := ip[/cidr]
Optional create options:
family { inet | inet6 }
The protocol family of the IP addresses to be stored in the set.
The default is inet, i.e IPv4.
hashsize value
The initial hash size for the set, default is 1024. The hash
size must be a power of two, the kernel automatically rounds up
non power of two hash sizes to the first correct value.
maxelem value
The maximal number of elements which can be stored in the set,
default 65536.
For the inet family one can add or delete multiple entries by specify‐
ing a range, which is converted internally to network(s) equal to the
range:
netaddr := { ip[/cidr] | fromaddr-toaddr }
When adding/deleting/testing entries, if the cidr prefix parameter is
not specified, then the host prefix value is assumed. When
adding/deleting entries, the exact element is added/deleted and over‐
lapping elements are not checked by the kernel. When testing entries,
if a host address is tested, then the kernel tries to match the host
address in the networks added to the set and reports the result accord‐
ingly.
From the set netfilter match point of view the searching for a match
always starts from the smallest size of netblock (most specific
prefix) to the largest one (least specific prefix) added to the set.
When adding/deleting IP addresses to the set by the SET netfilter
target, it will be added/deleted by the most specific prefix which
can be found in the set, or by the host prefix value if the set is
empty.
The lookup time grows linearly with the number of the different prefix
values added to the set.
Example:
ipset create foo hash:net
ipset add foo 192.168.0.0/24
ipset add foo 10.1.0.0/16
ipset add foo 192.168.0/24
When matching the elements in the set above, all IP addresses will
match from the networks 192.168.0.0/24, 10.1.0.0/16 and 192.168.0/24
except 192.168.0/30.
hash:ip,port
The hash:ip,port set type uses a hash to store IP address and port num‐
ber pairs. The port number is interpreted together with a protocol
(default TCP) and zero protocol number cannot be used.
CREATE-OPTIONS := [ family { inet | inet6 } ] | [ hashsize value ] [
maxelem value ] [ timeout value ]
ADD-ENTRY := ipaddr,[proto:]port
ADD-OPTIONS := [ timeout value ]
DEL-ENTRY := ipaddr,[proto:]port
TEST-ENTRY := ipaddr,[proto:]port
Optional create options:
family { inet | inet6 }
The protocol family of the IP addresses to be stored in the set.
The default is inet, i.e IPv4.
hashsize value
The initial hash size for the set, default is 1024. The hash
size must be a power of two, the kernel automatically rounds up
non power of two hash sizes to the first correct value
maxelem value
The maximal number of elements which can be stored in the set,
default 65536.
For the inet family one can add or delete multiple entries by specify‐
ing a range or a network of IPv4 addresses in the IP address part of
the entry:
ipaddr := { ip | fromaddr-toaddr | ip/cidr }
The [proto:]port part of the elements may be expressed in the following
forms, where the range variations are valid when adding or deleting
entries:
portname[-portname]
TCP port or range of ports expressed in TCP portname identifiers
from /etc/services
portnumber[-portnumber]
TCP port or range of ports expressed in TCP port numbers
tcp|sctp|udp|udplite:portname|portnumber[-portname|portnumber]
TCP, SCTP, UDP or UDPLITE port or port range expressed in port
name(s) or port number(s)
icmp:codename|type/code
ICMP codename or type/code. The supported ICMP codename identi‐
fiers can always be listed by the help command.
icmpv6:codename|type/code
ICMPv6 codename or type/code. The supported ICMPv6 codename
identifiers can always be listed by the help command.
proto:0
All other protocols, as an identifier from /etc/protocols or
number. The pseudo port number must be zero.
The hash:ip,port type of sets require two src/dst parameters of the set
match and SET target kernel modules.
Examples:
ipset create foo hash:ip,port
ipset add foo 192.168.1.0/24,80-82
ipset add foo 192.168.1.1,udp:53
ipset add foo 192.168.1.1,vrrp:0
ipset test foo 192.168.1.1,80
hash:net,port
The hash:net,port set type uses a hash to store different sized IP net‐
work address and port pairs. The port number is interpreted together
with a protocol (default TCP) and zero protocol number cannot be used.
Network address with zero prefix size is not accepted either.
CREATE-OPTIONS := [ family { inet | inet6 } ] | [ hashsize value ] [
maxelem value ] [ timeout value ]
ADD-ENTRY := netaddr,[proto:]port
ADD-OPTIONS := [ timeout value ]
DEL-ENTRY := netaddr,[proto:]port
TEST-ENTRY := netaddr,[proto:]port
where netaddr := ip[/cidr]
Optional create options:
family { inet | inet6 }
The protocol family of the IP addresses to be stored in the set.
The default is inet, i.e IPv4.
hashsize value
The initial hash size for the set, default is 1024. The hash
size must be a power of two, the kernel automatically rounds up
non power of two hash sizes to the first correct value.
maxelem value
The maximal number of elements which can be stored in the set,
default 65536.
For the netaddr part of the elements see the description at the
hash:net set type. For the [proto:]port part of the elements see the
description at the hash:ip,port set type.
When adding/deleting/testing entries, if the cidr prefix parameter is
not specified, then the host prefix value is assumed. When
adding/deleting entries, the exact element is added/deleted and over‐
lapping elements are not checked by the kernel. When testing entries,
if a host address is tested, then the kernel tries to match the host
address in the networks added to the set and reports the result accord‐
ingly.
From the set netfilter match point of view the searching for a match
always starts from the smallest size of netblock (most specific
prefix) to the largest one (least specific prefix) added to the set.
When adding/deleting IP addresses to the set by the SET netfilter
target, it will be added/deleted by the most specific prefix which
can be found in the set, or by the host prefix value if the set is
empty.
The lookup time grows linearly with the number of the different prefix
values added to the set.
Examples:
ipset create foo hash:net,port
ipset add foo 192.168.0/24,25
ipset add foo 10.1.0.0/16,80
ipset test foo 192.168.0/24,25
hash:ip,port,ip
The hash:ip,port,ip set type uses a hash to store IP address, port num‐
ber and a second IP address triples. The port number is interpreted
together with a protocol (default TCP) and zero protocol number cannot
be used.
CREATE-OPTIONS := [ family { inet | inet6 } ] | [ hashsize value ] [
maxelem value ] [ timeout value ]
ADD-ENTRY := ipaddr,[proto:]port,ip
ADD-OPTIONS := [ timeout value ]
DEL-ENTRY := ipaddr,[proto:]port,ip
TEST-ENTRY := ipaddr,[proto:]port,ip
For the first ipaddr and [proto:]port parts of the elements see the
descriptions at the hash:ip,port set type.
Optional create options:
family { inet | inet6 }
The protocol family of the IP addresses to be stored in the set.
The default is inet, i.e IPv4.
hashsize value
The initial hash size for the set, default is 1024. The hash
size must be a power of two, the kernel automatically rounds up
non power of two hash sizes to the first correct value.
maxelem value
The maximal number of elements which can be stored in the set,
default 65536.
The hash:ip,port,ip type of sets require three src/dst parameters of
the set match and SET target kernel modules.
Examples:
ipset create foo hash:ip,port,ip
ipset add foo 192.168.1.1,80,10.0.0.1
ipset test foo 192.168.1.1,udp:53,10.0.0.1
hash:ip,port,net
The hash:ip,port,net set type uses a hash to store IP address, port
number and IP network address triples. The port number is interpreted
together with a protocol (default TCP) and zero protocol number cannot
be used. Network address with zero prefix size cannot be stored either.
CREATE-OPTIONS := [ family { inet | inet6 } ] | [ hashsize value ] [
maxelem value ] [ timeout value ]
ADD-ENTRY := ipaddr,[proto:]port,netaddr
ADD-OPTIONS := [ timeout value ]
DEL-ENTRY := ipaddr,[proto:]port,netaddr
TEST-ENTRY := ipaddr,[proto:]port,netaddr
where netaddr := ip[/cidr]
For the ipaddr and [proto:]port parts of the elements see the descrip‐
tions at the hash:ip,port set type. For the netaddr part of the ele‐
ments see the description at the hash:net set type.
Optional create options:
family { inet | inet6 }
The protocol family of the IP addresses to be stored in the set.
The default is inet, i.e IPv4.
hashsize value
The initial hash size for the set, default is 1024. The hash
size must be a power of two, the kernel automatically rounds up
non power of two hash sizes to the first correct value.
maxelem value
The maximal number of elements which can be stored in the set,
default 65536.
From the set netfilter match point of view the searching for a match
always starts from the smallest size of netblock (most specific
cidr) to the largest one (least specific cidr) added to the set. When
adding/deleting triples to the set by the SET netfilter target, it
will be added/deleted by the most specific cidr which can be found in
the set, or by the host cidr value if the set is empty.
The lookup time grows linearly with the number of the different cidr
values added to the set.
The hash:ip,port,net type of sets require three src/dst parameters of
the set match and SET target kernel modules.
Examples:
ipset create foo hash:ip,port,net
ipset add foo 192.168.1,80,10.0.0/24
ipset add foo 192.168.2,25,10.1.0.0/16
ipset test foo 192.168.1,80.10.0.0/24
hash:net,iface
The hash:net,iface set type uses a hash to store different sized IP
network address and interface name pairs. Network address with zero
prefix size is not accepted.
CREATE-OPTIONS := [ family { inet | inet6 } ] | [ hashsize value ] [
maxelem value ] [ timeout value ]
ADD-ENTRY := netaddr,[physdev:]iface
ADD-OPTIONS := [ timeout value ]
DEL-ENTRY := netaddr,[physdev:]iface
TEST-ENTRY := netaddr,[physdev:]iface
where netaddr := ip[/cidr]
Optional create options:
family { inet | inet6 }
The protocol family of the IP addresses to be stored in the set.
The default is inet, i.e IPv4.
hashsize value
The initial hash size for the set, default is 1024. The hash
size must be a power of two, the kernel automatically rounds up
non power of two hash sizes to the first correct value.
maxelem value
The maximal number of elements which can be stored in the set,
default 65536.
For the netaddr part of the elements see the description at the
hash:net set type.
When adding/deleting/testing entries, if the cidr prefix parameter is
not specified, then the host prefix value is assumed. When
adding/deleting entries, the exact element is added/deleted and over‐
lapping elements are not checked by the kernel. When testing entries,
if a host address is tested, then the kernel tries to match the host
address in the networks added to the set and reports the result accord‐
ingly.
From the set netfilter match point of view the searching for a match
always starts from the smallest size of netblock (most specific
prefix) to the largest one (least specific prefix) added to the set.
When adding/deleting IP addresses to the set by the SET netfilter
target, it will be added/deleted by the most specific prefix which
can be found in the set, or by the host prefix value if the set is
empty.
The second direction parameter of the set match and SET target modules
corresponds to the incoming/outgoing interface : src to the incoming,
while dst to the outgoing. When the interface is flagged with physdev:,
the interface is interpreted as the incoming/outgoing bridge port.
The lookup time grows linearly with the number of the different prefix
values added to the set.
The internal restriction of the hash:net,iface set type is that the
same network prefix cannot be stored with more than 64 different inter‐
faces in a single set.
Examples:
ipset create foo hash:net,iface
ipset add foo 192.168.0/24,eth0
ipset add foo 10.1.0.0/16,eth1
ipset test foo 192.168.0/24,eth0
list:set
The list:set type uses a simple list in which you can store set names.
CREATE-OPTIONS := [ size value ] [ timeout value ]
ADD-ENTRY := setname [ { before | after } setname ]
ADD-OPTIONS := [ timeout value ]
DEL-ENTRY := setname [ { before | after } setname ]
TEST-ENTRY := setname [ { before | after } setname ]
Optional create options:
size value
The size of the list, the default is 8.
By the ipset commad you can add, delete and test set names in a
list:set type of set.
By the set match or SET target of netfilter you can test, add or delete
entries in the sets added to the list:set type of set. The match will
try to find a matching entry in the sets and the target will try to add
an entry to the first set to which it can be added. The number of
direction options of the match and target are important: sets which
require more parameters than specified are skipped, while sets with
equal or less parameters are checked, elements added/deleted. For exam‐
ple if a and b are list:set type of sets then in the command
iptables -m set --match-set a src,dst -j SET --add-set b src,dst
the match and target will skip any set in a and b which stores data
triples, but will match all sets with single or double data storage in
a set and stop matching at the first successful set, and add src to the
first single or src,dst to the first double data storage set in b to
which the entry can be added. You can imagine a list:set type of set as
an ordered union of the set elements.
Please note: by the ipset commad you can add, delete and test the set‐
names in a list:set type of set, and not the presence of a set's member
(such as an IP address).
GENERAL RESTRICTIONS
Zero valued set entries cannot be used with hash methods. Zero protocol
value with ports cannot be used.
COMMENTS
If you want to store same size subnets from a given network (say /24
blocks from a /8 network), use the bitmap:ip set type. If you want to
store random same size networks (say random /24 blocks), use the
hash:ip set type. If you have got random size of netblocks, use
hash:net.
Backward compatibility is maintained and old ipset syntax is still sup‐
ported.
The iptree and iptreemap set types are removed: if you refer to them,
they are automatically replaced by hash:ip type of sets.
DIAGNOSTICS
Various error messages are printed to standard error. The exit code is
0 for correct functioning.
BUGS
Bugs? No, just funny features. :-) OK, just kidding...
SEE ALSOiptables(8), ip6tables(8)AUTHORS
Jozsef Kadlecsik wrote ipset, which is based on ippool by Joakim Axels‐
son, Patrick Schaaf and Martin Josefsson.
Sven Wegener wrote the iptreemap type.
LAST REMARK
I stand on the shoulders of giants.
Jozsef Kadlecsik Oct 15, 2010 IPSET(8)
