shorewall_code/Shorewall-docs2/myfiles.xml
2004-02-15 17:29:58 +00:00

697 lines
32 KiB
XML

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE article PUBLIC "-//OASIS//DTD DocBook XML V4.2//EN"
"http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd">
<article>
<!--$Id$-->
<articleinfo>
<title>About My Network</title>
<authorgroup>
<author>
<firstname>Tom</firstname>
<surname>Eastep</surname>
</author>
</authorgroup>
<pubdate>2004-02-14</pubdate>
<copyright>
<year>2001-2004</year>
<holder>Thomas M. Eastep</holder>
</copyright>
<legalnotice>
<para>Permission is granted to copy, distribute and/or modify this
document under the terms of the GNU Free Documentation License, Version
1.2 or any later version published by the Free Software Foundation; with
no Invariant Sections, with no Front-Cover, and with no Back-Cover
Texts. A copy of the license is included in the section entitled
<quote><ulink url="GnuCopyright.htm">GNU Free Documentation License</ulink></quote>.</para>
</legalnotice>
</articleinfo>
<section>
<title>My Current Network</title>
<caution>
<para>I use a combination of One-to-one NAT and Proxy ARP, neither of
which are relevant to a simple configuration with a single public IP
address. If you have just a single public IP address, most of what you
see here won&#39;t apply to your setup so beware of copying parts of
this configuration and expecting them to work for you. What you copy may
or may not work in your configuration.</para>
</caution>
<caution>
<para>The configuration shown here corresponds to Shorewall version
2.0.0-Beta2. It may use features not available in earlier Shorewall
releases.</para>
</caution>
<para>I have DSL service and have 5 static IP addresses
(206.124.146.176-180). My DSL <quote>modem</quote> (Fujitsu Speedport) is
connected to eth0. I have a local network connected to eth2 (subnet
192.168.1.0/24), a DMZ connected to eth1 (206.124.146.176/32) and a
Wireless network connected to eth3 (192.168.3.0/24). Note that the IP
address of eth1 is a duplicate of one on eth0.</para>
<para>I use:</para>
<itemizedlist>
<listitem>
<para>One-to-one NAT for Ursa (my personal system that dual-boots
Mandrake 9.2 and Windows XP) - Internal address 192.168.1.5 and
external address 206.124.146.178.</para>
</listitem>
<listitem>
<para>One-to-one NAT for EastepLaptop (My work system -- Windows XP
SP2). Internal address 192.168.1.7 and external address
206.124.146.180.</para>
</listitem>
<listitem>
<para>SNAT through 206.124.146.179 for&#x00A0; my SuSE 9.0 Linux
system (Wookie), my Wife&#39;s Windows XP system (Tarry), and
our&#x00A0; Windows XP laptop (Tipper) which connects through the
Wireless Access Point (wap) via a Wireless Bridge (bridge).<note><para>While
the distance between the WAP and where I usually use the laptop
isn&#39;t very far (25 feet or so), using a WAC11 (CardBus wireless
card) has proved very unsatisfactory (lots of lost connections). By
replacing the WAC11 with the WET11 wireless bridge, I have virtually
eliminated these problems (Being an old radio tinkerer (K7JPV), I was
also able to eliminate the disconnects by hanging a piece of aluminum
foil on the family room wall. Needless to say, my wife Tarry rejected
that as a permanent solution :-).</para></note></para>
</listitem>
</itemizedlist>
<para>The firewall runs on a 256MB PII/233 with Debian Sarge (Testing).</para>
<para>Wookie, Ursa and the Firewall all run Samba and the Firewall acts as
a WINS server.</para>
<para>The wireless network connects to eth3 via a LinkSys WAP11.&#x00A0;
In additional to using the rather weak WEP 40-bit encryption (64-bit with
the 24-bit preamble), I use <ulink url="MAC_Validation.html">MAC
verification</ulink>. This is still a weak combination and if I lived near
a wireless <quote>hot spot</quote>, I would probably add IPSEC or
something similar to my WiFi-&#62;local connections.</para>
<para>The single system in the DMZ (address 206.124.146.177) runs postfix,
Courier IMAP (imaps and pop3), DNS, a Web server (Apache) and an FTP
server (Pure-ftpd) under RedHat 9.0. The system also runs fetchmail to
fetch our email from our old and current ISPs. That server is managed
through Proxy ARP.</para>
<para>The firewall system itself runs a DHCP server that serves the local
network.</para>
<para>All administration and publishing is done using ssh/scp. I have a
desktop environment installed on the firewall but I am not usually logged
in to it. X applications tunnel through SSH to Ursa. The server also has a
desktop environment installed and that desktop environment is available
via XDMCP from the local zone. For the most part though, X tunneled
through SSH is used for server administration and the server runs at run
level 3 (multi-user console mode on RedHat).</para>
<para>I run an SNMP server on my firewall to serve <ulink
url="http://www.ee.ethz.ch/~oetiker/webtools/mrtg/">MRTG</ulink> running
in the DMZ.<graphic align="center" fileref="images/network.png" />The
ethernet interface in the Server is configured with IP address
206.124.146.177, netmask 255.255.255.0. The server&#39;s default gateway
is 206.124.146.254 (Router at my ISP. This is the same default gateway
used by the firewall itself). On the firewall, an entry in my
/etc/network/interfaces file (see below) adds a host route to
206.124.146.177 through eth1 when that interface is brought up.</para>
<para>Ursa (192.168.1.5 A.K.A. 206.124.146.178) runs a PPTP server for
Road Warrior access.</para>
<section>
<title>Shorewall.conf</title>
<blockquote>
<programlisting>LOGFILE=/var/log/messages
LOGRATE=
LOGBURST=
LOGUNCLEAN=$LOG
BLACKLIST_LOGLEVEL=
LOGNEWNOTSYN=$LOG
MACLIST_LOG_LEVEL=$LOG
TCP_FLAGS_LOG_LEVEL=$LOG
RFC1918_LOG_LEVEL=$LOG
SMURF_LOG_LEVEL=
PATH=/sbin:/bin:/usr/sbin:/usr/bin:/usr/local/bin:/usr/local/sbin
SHOREWALL_SHELL=/bin/ash
SUBSYSLOCK= #I run Debian which doesn&#39;t use service locks
STATEDIR=/var/state/shorewall
MODULESDIR=
FW=fw
IP_FORWARDING=On
ADD_IP_ALIASES=Yes
ADD_SNAT_ALIASES=Yes
TC_ENABLED=Yes
CLEAR_TC=No
MARK_IN_FORWARD_CHAIN=No
CLAMPMSS=Yes
ROUTE_FILTER=No
DETECT_DNAT_IPADDRS=Yes
MUTEX_TIMEOUT=60
NEWNOTSYN=Yes
BLACKLISTNEWONLY=Yes
BLACKLIST_DISPOSITION=DROP
MACLIST_DISPOSITION=REJECT
TCP_FLAGS_DISPOSITION=DROP
</programlisting>
</blockquote>
</section>
<section>
<title>Params File (Edited)</title>
<blockquote>
<para><programlisting>MIRRORS=&#60;list of shorewall mirror ip addresses&#62;
NTPSERVERS=&#60;list of the NTP servers I sync with&#62;
TEXAS=&#60;ip address of gateway in Dallas&#62;
LOG=info</programlisting></para>
</blockquote>
</section>
<section>
<title>Zones File</title>
<blockquote>
<programlisting>#ZONE DISPLAY COMMENTS
net Internet Internet
WiFi Wireless Wireless Network on eth3
dmz DMZ Demilitarized zone
loc Local Local networks
tx Texas Peer Network in Dallas
#LAST LINE -- ADD YOUR ENTRIES ABOVE THIS ONE - DO NOT REMOVE</programlisting>
</blockquote>
</section>
<section>
<title>Interfaces File</title>
<blockquote>
<para>This is set up so that I can start the firewall before bringing
up my Ethernet interfaces.</para>
<programlisting>#ZONE INERFACE BROADCAST OPTIONS
net eth0 206.124.146.255 dhcp,norfc1918,routefilter,blacklist,tcpflags,nosmurfs
loc eth2 192.168.1.255 dhcp,detectnets
dmz eth1 -
WiFi eth3 192.168.3.255 dhcp,maclist,detectnets
- texas 192.168.9.255
#LAST LINE -- ADD YOUR ENTRIES ABOVE THIS ONE - DO NOT REMOVE</programlisting>
</blockquote>
</section>
<section>
<title>Hosts File</title>
<blockquote>
<programlisting>#ZONE HOST(S) OPTIONS
tx&#x00A0;&#x00A0;&#x00A0;&#x00A0;&#x00A0;&#x00A0;&#x00A0;&#x00A0;&#x00A0;&#x00A0;&#x00A0;&#x00A0;&#x00A0; texas:192.168.8.0/22
#LAST LINE -- ADD YOUR ENTRIES ABOVE THIS ONE - DO NOT REMOVE</programlisting>
</blockquote>
</section>
<section>
<title>Routestopped File</title>
<blockquote>
<programlisting>#INTERFACE HOST(S)
eth1 206.124.146.177
eth2 -
eth3 192.168.3.0/24
#LAST LINE -- ADD YOUR ENTRIES ABOVE THIS ONE - DO NOT REMOVE</programlisting>
</blockquote>
</section>
<section id="RFC1918">
<title>RFC1918 File</title>
<blockquote>
<para>I use a stripped-down file which doesn&#39;t have to be updated
when the IANA allocates a block of IP addresses.</para>
</blockquote>
<blockquote>
<programlisting>#SUBNET TARGET
169.254.0.0/16 DROP # DHCP autoconfig
172.16.0.0/12 logdrop # RFC 1918
192.0.2.0/24 logdrop # Example addresses
192.168.0.0/16 logdrop # RFC 1918
10.24.60.56 DROP # Some idiot in my broadcast domain
# has a box configured with this
# address.
10.0.0.0/8 logdrop # Reserved (RFC 1918)</programlisting>
</blockquote>
</section>
<section>
<title>Blacklist File (Partial)</title>
<blockquote>
<programlisting>#ADDRESS/SUBNET PROTOCOL PORT
0.0.0.0/0 udp 1434
0.0.0.0/0 tcp 1433
0.0.0.0/0 tcp 8081
0.0.0.0/0 tcp 57
#LAST LINE -- ADD YOUR ENTRIES ABOVE THIS ONE - DO NOT REMOVE</programlisting>
</blockquote>
</section>
<section>
<title>Policy File</title>
<blockquote>
<programlisting>#SOURCE DESTINATION POLICY LOG LEVEL BURST:LIMIT
fw fw ACCEPT # For testing fw-&#62;fw rules
loc net ACCEPT # Allow all net traffic from local net
$FW loc ACCEPT # Allow local access from the firewall
$FW tx ACCEPT # Allow firewall access to texas
loc tx ACCEPT # Allow local net access to texas
loc fw REJECT $LOG # Reject loc-&#62;fw and log
WiFi net ACCEPT # Allow internet access from wirless
net all DROP $LOG 10/sec:40 # Rate limit and
# DROP net-&#62;all
all all REJECT $LOG # Reject and log the rest
#LAST LINE -- ADD YOUR ENTRIES ABOVE THIS ONE - DO NOT REMOVE</programlisting>
</blockquote>
</section>
<section>
<title>Masq File</title>
<blockquote>
<para>Although most of our internal systems use one-to-one NAT, my
wife&#39;s system (192.168.1.4) uses IP Masquerading (actually SNAT)
as does my SuSE system (192.168.1.3), our laptop (192.168.3.8) and
visitors with laptops.</para>
<programlisting>#INTERFACE SUBNET ADDRESS
eth0:2 eth2 206.124.146.179
eth0 eth3 206.124.146.179
#LAST LINE -- ADD YOUR ENTRIES ABOVE THIS LINE -- DO NOT REMOVE
</programlisting>
</blockquote>
</section>
<section>
<title>NAT File</title>
<blockquote>
<programlisting>#EXTERNAL INTERFACE INTERNAL ALL INTERFACES LOCAL
206.124.146.178 eth0:0 192.168.1.5 No No
206.124.146.180 eth0:1 192.168.1.7 No No
#
# The following entry allows the server to be accessed through an address in
# the local network. This is convenient when I&#39;m on the road and connected
# to the PPTP server. By doing this, I don&#39;t need to set my client&#39;s default
# gateway to route through the tunnel.
#
192.168.1.193 eth2:0 206.124.146.177 No No
#LAST LINE -- ADD YOUR ENTRIES ABOVE THIS LINE -- DO NOT REMOVE</programlisting>
</blockquote>
</section>
<section id="ProxyARP">
<title>Proxy ARP File</title>
<blockquote>
<programlisting>#ADDRESS INTERFACE EXTERNAL HAVEROUTE PERSISTENT
206.124.146.177 eth1 eth0 Yes
#LAST LINE -- ADD YOUR ENTRIES BEFORE THIS ONE -- DO NOT REMOVE</programlisting>
</blockquote>
</section>
<section>
<title>Tunnels File (Shell variable TEXAS set in /etc/shorewall/params)</title>
<blockquote>
<programlisting>#TYPE ZONE GATEWAY GATEWAY ZONE PORT
gre net $TEXAS
#LAST LINE -- ADD YOUR ENTRIES BEFORE THIS ONE -- DO NOT REMOVE</programlisting>
</blockquote>
</section>
<section id="Actions">
<title>Actions File</title>
<blockquote>
<programlisting>#ACTION
Mirrors #Accept traffic from the Shorewall Mirror sites
#LAST LINE - ADD YOUR ENTRIES ABOVE THIS ONE - DO NOT REMOVE</programlisting>
</blockquote>
</section>
<section>
<title>action.Mirrors File</title>
<blockquote>
<para>The $MIRRORS variable expands to a list of approximately 10 IP
addresses. So moving these checks into a separate chain reduces the
number of rules that most net-&#62;dmz traffic needs to traverse.</para>
<programlisting>#TARGET SOURCE DEST PROTO DEST SOURCE ORIGINAL RATE
# PORT PORT(S) DEST LIMIT
ACCEPT $MIRRORS
#LAST LINE -- ADD YOUR ENTRIES BEFORE THIS ONE -- DO NOT REMOVE</programlisting>
</blockquote>
</section>
<section>
<title>/etc/shorewall/action.Drop</title>
<blockquote>
<para>This is my common action for the DROP policy. It is like the
standard <emphasis role="bold">Drop</emphasis> action except that it
allows <quote>Ping</quote>.</para>
<programlisting>#TARGET SOURCE DEST PROTO DEST SOURCE RATE USER/
# PORT(S) PORT(S) LIMIT GROUP
RejectAuth
AllowPing
dropBcast
DropSMB
DropUPnP
dropNonSyn
DropDNSrep</programlisting>
</blockquote>
</section>
<section>
<title>/etc/shorewall/action.Reject</title>
<blockquote>
<para>This is my common action for the REJECT policy. It is like the
standard <emphasis role="bold">Reject</emphasis> action except that it
allows <quote>Ping</quote> and contains one rule that guards against
log flooding by broken software running in my local zone.</para>
<programlisting>#TARGET SOURCE DEST PROTO DEST SOURCE RATE USER/
# PORT(S) PORT(S) LIMIT GROUP
RejectAuth
AllowPing
dropBcast
RejectSMB
DropUPnP
dropNonSyn
DropDNSrep
DROP loc:eth2:!192.168.1.0/24 #So that my braindead Windows[tm] XP system doesn&#39;t flood my log
#with NTP requests with a source address in 16.0.0.0/8 (address of
#its PPTP tunnel to HP).</programlisting>
</blockquote>
</section>
<section>
<title>Rules File (The shell variables are set in /etc/shorewall/params)</title>
<blockquote>
<programlisting>###############################################################################################################################################################################
#RESULT CLIENT(S) SERVER(S) PROTO PORT(S) CLIENT ORIGINAL RATE USER
# PORT(S) DEST:SNAT SET
###############################################################################################################################################################################
# Local Network to Internet - Reject attempts by Trojans to call home
#
REJECT:$LOG loc net tcp 6667
#
# Stop NETBIOS crap since our policy is ACCEPT
#
REJECT loc net tcp 137,445
REJECT loc net udp 137:139
#
DROP loc:!192.168.1.0/24 net
QUEUE loc net udp
QUEUE loc fw udp
QUEUE loc net tcp
###############################################################################################################################################################################
# Local Network to Firewall
#
DROP loc:!192.168.1.0/24 fw
ACCEPT loc fw tcp ssh,time,10000,swat,137,139,445
ACCEPT loc fw udp snmp,ntp,445
ACCEPT loc fw udp 137:139
ACCEPT loc fw udp 1024: 137
###############################################################################################################################################################################
# Local Network to DMZ
#
DROP loc:!192.168.1.0/24 dmz
REJECT loc dmz tcp 465
ACCEPT loc dmz udp domain,xdmcp
ACCEPT loc dmz tcp www,smtp,domain,ssh,imap,https,imaps,cvspserver,ftp,10000,8080,10027,pop3 -
###############################################################################################################################################################################
# Internet to DMZ
#
DNAT- net dmz:206.124.146.177 tcp smtp - 206.124.146.179,206.124.146.178
ACCEPT net dmz tcp smtp,www,ftp,imaps,domain,cvspserver,https -
ACCEPT net dmz udp domain
ACCEPT net dmz udp 33434:33436
Mirrors net dmz tcp rsync
#ACCEPT:$LOG net dmz tcp 32768:61000 20
###############################################################################################################################################################################
#
# Net to Local
#
# When I&#39;m &#34;on the road&#34;, the following two rules allow me VPN access back home.
#
ACCEPT net loc:192.168.1.5 tcp 1723
ACCEPT net loc:192.168.1.5 gre
#
# ICQ
#
ACCEPT net loc:192.168.1.5 tcp 4000:4100
#
# Real Audio
#
ACCEPT net loc:192.168.1.5 udp 6970:7170
#
# Overnet
#
#ACCEPT net loc:192.168.1.5 tcp 4662
#ACCEPT net loc:192.168.1.5 udp 12112
###############################################################################################################################################################################
# DMZ to Internet
#
ACCEPT dmz net tcp smtp,domain,www,https,whois,echo,2702,21,2703,ssh,8080
ACCEPT dmz net udp domain
ACCEPT dmz net:$POPSERVERS tcp pop3
#ACCEPT dmz net:206.191.151.2 tcp pop3
#ACCEPT dmz net:66.216.26.115 tcp pop3
#
# Something is wrong with the FTP connection tracking code or there is some client out there
# that is sending a PORT command which that code doesn&#39;t understand. Either way,
# the following works around the problem.
#
ACCEPT:$LOG dmz net tcp 1024: 20
###############################################################################################################################################################################
# DMZ to Firewall -- ntp &#38; snmp, Silently reject Auth
#
ACCEPT dmz fw udp ntp ntp
ACCEPT dmz fw tcp snmp,ssh
ACCEPT dmz fw udp snmp
REJECT dmz fw tcp auth
###############################################################################################################################################################################
# DMZ to Internet
#
ACCEPT dmz net tcp smtp,domain,www,https,whois,echo,2702,21,2703,ssh,8080
ACCEPT dmz net udp domain
ACCEPT dmz net:$POPSERVERS tcp pop3
#ACCEPT dmz net:206.191.151.2 tcp pop3
#ACCEPT dmz net:66.216.26.115 tcp pop3
#
# Something is wrong with the FTP connection tracking code or there is some client out there
# that is sending a PORT command which that code doesn&#39;t understand. Either way,
# the following works around the problem.
#
ACCEPT:$LOG dmz net tcp 1024: 20
###############################################################################################################################################################################
# DMZ to Firewall -- ntp &#38; snmp, Silently reject Auth
#
ACCEPT dmz fw udp ntp ntp
ACCEPT dmz fw tcp snmp,ssh
ACCEPT dmz fw udp snmp
REJECT dmz fw tcp auth
###############################################################################################################################################################################
#
# DMZ to Local Network
#
ACCEPT dmz loc tcp smtp,6001:6010
ACCEPT dmz loc tcp 111
ACCEPT dmz loc udp
###############################################################################################################################################################################
# Internet to Firewall
#
REJECT net fw tcp www
ACCEPT net dmz udp 33434:33435
###############################################################################################################################################################################
# WIFI to Firewall
#
ACCEPT WiFi fw tcp ssh,137,139,445
ACCEPT WiFi fw udp 137:139,445
ACCEPT WiFi fw udp 1024: 137
ACCEPT WiFi fw udp ntp ntp
###############################################################################################################################################################################
# Firewall to WIFI
#
ACCEPT fw WiFi tcp 137,139,445
ACCEPT fw WiFi udp 137:139,445
ACCEPT fw WiFi udp 1024: 137
ACCEPT fw WiFi udp ntp ntp
##############################################################################################################################################################################
# WIFI to DMZ
#
DNAT- WiFi dmz:206.124.146.177 all - - 192.168.1.193
ACCEPT WiFi dmz tcp smtp,www,ftp,imaps,domain,https,ssh,8080 -
ACCEPT WiFi dmz udp domain
##############################################################################################################################################################################
# WIFI to loc
#
ACCEPT WiFi loc udp 137:139
ACCEPT WiFi loc tcp 22,80,137,139,445,901,3389
ACCEPT WiFi loc udp 1024: 137
ACCEPT WiFi loc udp 177
##############################################################################################################################################################################
# loc to WiFi
#
ACCEPT loc WiFi udp 137:139
ACCEPT loc WiFi tcp 137,139,445
ACCEPT loc WiFi udp 1024: 137
ACCEPT loc WiFi tcp 6000:6010
###############################################################################################################################################################################
# Firewall to Internet
#
ACCEPT fw net:$NTPSERVERS udp ntp ntp
#ACCEPT fw net:$POPSERVERS tcp pop3
ACCEPT fw net udp domain
ACCEPT fw net tcp domain,www,https,ssh,1723,whois,1863,ftp,2702,2703,7
ACCEPT fw net udp 33435:33535
ACCEPT fw net icmp
###############################################################################################################################################################################
# Firewall to DMZ
#
ACCEPT fw dmz tcp www,ftp,ssh,smtp
ACCEPT fw dmz udp domain
REJECT fw dmz udp 137:139
###############################################################################################################################################################################
# Ping
#
ACCEPT all all icmp 8
#LAST LINE -- ADD YOUR ENTRIES BEFORE THIS ONE -- DO NOT REMOVE</programlisting>
</blockquote>
</section>
<section id="Interfaces">
<title>/etc/network/interfaces</title>
<blockquote>
<para>This file is Debian specific. My additional entry (which is
displayed in <emphasis role="bold">bold type</emphasis>) adds a route
to my DMZ server when eth1 is brought up. It allows me to enter
<quote>Yes</quote> in the HAVEROUTE column of <link linkend="ProxyARP">my
Proxy ARP file</link>.</para>
<programlisting>...
auto eth1
iface eth1 inet static
address 206.124.146.176
netmask 255.255.255.255
broadcast 0.0.0.0
<emphasis role="bold">up ip route add 206.124.146.177 dev eth1
</emphasis>...</programlisting>
</blockquote>
</section>
<section id="Dhcpd">
<title>/etc/dhcpd.conf (MAC Addresses Omitted)</title>
<blockquote>
<para>While this is a little off-topic, I&#39;ve included it to show
how to set up DHCP on two interfaces.<programlisting>default-lease-time 67200; max-lease-time 67200;
get-lease-hostnames on;
group {
option subnet-mask 255.255.255.0;
option broadcast-address 192.168.1.255;
option routers 192.168.1.254;
option ntp-servers 192.168.1.254;
option domain-name-servers 192.168.1.193;
option netbios-name-servers 192.168.1.254;
option domain-name &#34;shorewall.net&#34;;
option netbios-dd-server 192.168.1.254;
option netbios-node-type 8;
option netbios-scope &#34;&#34;;
subnet 192.168.1.0 netmask 255.255.255.0 {
range 192.168.1.11 192.168.1.20;
}
host ursa.shorewall.net {
hardware ethernet …;
fixed-address 192.168.1.5;
}
host eastept1 {
hardware ethernet …;
fixed-address 192.168.1.7;
}
host tarry {
hardware ethernet …;
fixed-address 192.168.1.4;
}
host wookie.shorewall.net {
hardware ethernet …;
fixed-address 192.168.1.3;
}
host testws.shorewall.net {
hardware ethernet …;
fixed-address 192.168.1.6;
}
host printer.shorewall.net {
hardware ethernet …;
fixed-address 192.168.1.10;
}
}
group {
option subnet-mask 255.255.255.0;
option broadcast-address 192.168.3.255;
option routers 192.168.3.254;
option ntp-servers 192.168.3.254;
option domain-name-servers 206.124.146.177;
option netbios-name-servers 192.168.3.254;
option domain-name &#34;shorewall.net&#34;;
option netbios-dd-server 192.168.3.254;
option netbios-node-type 8;
option netbios-scope &#34;&#34;;
subnet 192.168.3.0 netmask 255.255.255.0 {
range 192.168.3.11 192.168.3.20;
}
host easteplaptop {
hardware ethernet …;
fixed-address 192.168.3.7;
}
host tipper.shorewall.net {
hardware ethernet …;
fixed-address 192.168.3.8;
}</programlisting></para>
</blockquote>
</section>
</section>
</article>