About My Network
Tom
Eastep
2004-09-06
2001-2004
Thomas M. Eastep
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
GNU Free Documentation
License
.
My Current Network
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'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 for you.
The configuration shown here corresponds to Shorewall version
2.1.7. My configuration uses features not available in earlier Shorewall
releases.
I have DSL service and have 5 static IP addresses
(206.124.146.176-180). My DSL modem
(Westell 2200) is
connected to eth0 and has IP address 192.168.1.1 (factory default). The
modem is configured in bridge
mode so PPPoE is not
involved. I have a local network connected to eth2 (subnet 192.168.1.0/24)
and a DMZ connected to eth1 (206.124.146.176/32). Note that I configure
the same IP address on both eth0
and eth1.
In this configuration:
I use one-to-one NAT for Ursa (my personal system that run SuSE
9.1) - Internal address 192.168.1.5 and external address
206.124.146.178.
I use one-to-one NAT for EastepLaptop (My work system -- Windows
XP SP1). Internal address 192.168.1.7 and external address
206.124.146.180.
I use SNAT through 206.124.146.179 for my Wife's Windows XP
system Tarry
, and our dual-booting (Windows
XP/SuSE 9.1) laptop Tipper
which connects through the
Wireless Access Point (wap) via a Wireless Bridge (wet).
While the distance between the WAP and where I usually use
the laptop isn'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 :-).
I have Ursa (193.168.1.5/206.124.146.178) configured as a 2-port
bridge.
Squid runs on the firewall and is configured as a transparent
proxy.
The firewall runs on a 384MB K-6/II with SuSE 9.1.
Ursa runs Samba for file sharing with the Windows systems..
The wireless network connects to Ursa's eth0 via a LinkSys
WAP11. In additional to using the rather weak WEP 40-bit encryption
(64-bit with the 24-bit preamble), I use MAC verification. This is still a weak
combination and if I lived near a wireless hot spot
, I
would probably add IPSEC or something similar to my WiFi->local
connections.
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 Fedora Core 2. The system also runs fetchmail to
fetch our email from our old and current ISPs. That server is managed
through Proxy ARP.
The firewall system itself runs a DHCP server that serves the local
network.
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 Fedora).
I run an SNMP server on my firewall to serve MRTG running
in the DMZ.
The ethernet interface in the Server is configured with IP address
206.124.146.177, netmask 255.255.255.0. The server'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.
Tarry (192.168.1.4) runs a PPTP server for Road Warrior access from
my work laptop and the Firewall is configured with IPSEC for tunnel mode
road warrior access from Tipper.
![]()
Firewall Configuration
Shorewall.conf
LOGFILE=/var/log/messages
LOGFORMAT="Shorewall:%s:%s "
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=/usr/local/sbin:/sbin:/bin:/usr/sbin:/usr/bin:/usr/local/bin
SHOREWALL_SHELL=/bin/ash
SUBSYSLOCK=
STATEDIR=/var/state/shorewall
MODULESDIR=
CONFIG_PATH=/etc/shorewall:/etc/shorewall/actiondir:/usr/share/shorewall
RESTOREFILE=standard
FW=fw
IP_FORWARDING=On
ADD_IP_ALIASES=Yes
ADD_SNAT_ALIASES=Yes
TC_ENABLED=Yes
CLEAR_TC=Yes
MARK_IN_FORWARD_CHAIN=No
CLAMPMSS=Yes
ROUTE_FILTER=No
DETECT_DNAT_IPADDRS=Yes
MUTEX_TIMEOUT=60
NEWNOTSYN=Yes
BLACKLISTNEWONLY=Yes
DYNAMIC_ZONES=No
DISABLE_IPV6=Yes
PKTTYPE=No
BLACKLIST_DISPOSITION=DROP
MACLIST_DISPOSITION=REJECT
TCP_FLAGS_DISPOSITION=DROP
Params File (Edited)
MIRRORS=<list of shorewall mirror ip addresses>
NTPSERVERS=<list of the NTP servers I sync with>
TEXAS=<ip address of gateway in Plano>
OMAK=<ip address of tipper while we are at our second home>
LOG=info
EXT_IF=eth1
INT_IF=eth0
DMZ_IF=eth2
Zones File
#ZONE DISPLAY COMMENTS
net Internet Internet
dmz DMZ Demilitarized zone
loc Local Local networks
omak Omak Our Laptop at our second home
tx Texas Peer Network in Dallas
#LAST LINE - ADD YOUR ENTRIES ABOVE THIS ONE - DO NOT REMOVE
Interfaces File
This is set up so that I can start the firewall before bringing
up my Ethernet interfaces.
#ZONE INTERFACE BROADCAST OPTIONS
net $EXT_IF 206.124.146.255 dhcp,norfc1918,routefilter,blacklist,tcpflags,nosmurfs
loc $INT_IF detect dhcp
dmz $DMZ_IF -
- texas -
#LAST LINE - ADD YOUR ENTRIES ABOVE THIS ONE - DO NOT REMOVE
Hosts File
#ZONE HOST(S) OPTIONS
tx texas:192.168.8.0/22
omak $EXT_IF:$OMAK
#LAST LINE -- ADD YOUR ENTRIES ABOVE THIS ONE - DO NOT REMOVE
Ipsec File
#ZONE IPSEC OPTIONS IN OUT
# ONLY OPTIONS OPTIONS
omak yes mode=tunnel
#LAST LINE -- ADD YOUR ENTRIES BEFORE THIS ONE -- DO NOT REMOVE
Routestopped File
#INTERFACE HOST(S)
$DMZ_IF 206.124.146.177
$INT_IF -
$EXT_IF $OMAK
#LAST LINE -- ADD YOUR ENTRIES ABOVE THIS ONE - DO NOT REMOVE
Blacklist File (Partial)
#ADDRESS/SUBNET PROTOCOL PORT
0.0.0.0/0 udp 1434
0.0.0.0/0 tcp 1433
0.0.0.0/0 tcp 3127
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
RFC1918 File
Because my DSL modem has an RFC 1918 address (192.168.1.1) and
is connected to eth0, I need to make an exception for that address in
my rfc1918 file. I copied /usr/share/shorewall/rfc1918 to
/etc/shorewall/rfc1918 and changed it as follows:
#SUBNET TARGET
192.168.1.1 RETURN
172.16.0.0/12 logdrop # RFC 1918
192.168.0.0/16 logdrop # RFC 1918
10.0.0.0/8 logdrop # RFC 1918
#LAST LINE -- ADD YOUR ENTRIES BEFORE THIS ONE -- DO NOT REMOVE
Policy File
#SOURCE DESTINATION POLICY LOG LEVEL BURST:LIMIT
fw fw ACCEPT
loc net ACCEPT
fw sec ACCEPT
omak fw ACCEPT
fw omak ACCEPT
omak loc ACCEPT
loc omak ACCEPT
omak net NONE
net omak NONE
omak dmz NONE
dmz omak NONE
omak tx NONE
tx omak NONE
$FW loc ACCEPT #Firewall to Local
$FW tx ACCEPT
loc tx ACCEPT
loc fw REJECT $LOG
dmz tx ACCEPT
net all DROP $LOG 10/sec:40
all all REJECT $LOG
#LAST LINE -- ADD YOUR ENTRIES ABOVE THIS ONE - DO NOT REMOVE
Masq File
Although most of our internal systems use one-to-one NAT, my
wife's system (192.168.1.4) uses IP Masquerading (actually SNAT) as do
my SuSE system (192.168.1.3), our laptop (192.168.3.8) and visitors
with laptops.
The first entry allows access to the DSL modem and uses features
introduced in Shorewall 2.1.1. The leading plus sign ("+_") causes the
rule to be placed before rules generated by the /etc/shorewall/nat
file below. The double colons ("::") causes the entry to be exempt
from ADD_SNAT_ALIASES=Yes in my shorewall.conf file above.
#INTERFACE SUBNET ADDRESS
+$EXT_IF::192.168.1.1 0.0.0.0/0 192.168.1.254
$EXT_IF:2 eth2 206.124.146.179
#LAST LINE -- ADD YOUR ENTRIES ABOVE THIS LINE -- DO NOT REMOVE
NAT File
#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
#LAST LINE -- ADD YOUR ENTRIES ABOVE THIS LINE -- DO NOT REMOVE
Proxy ARP File
I configure the host route to 206.124.146.177 on eth1 using the Yast2 Network Interface
tool; the Gateway
is specified as 0.0.0.0 which
indicates that the host is directly attached to the LAN on that
interface.
#ADDRESS INTERFACE EXTERNAL HAVEROUTE PERSISTENT
206.124.146.177 eth1 eth0 Yes
192.168.1.1 eth0 eth2 yes # Allow access to DSL modem from the local zone
#LAST LINE -- ADD YOUR ENTRIES BEFORE THIS ONE -- DO NOT REMOVE
Tunnels File (Shell variable TEXAS set in
/etc/shorewall/params)
#TYPE ZONE GATEWAY GATEWAY ZONE PORT
gre net $TEXAS
ipsec:noah net $OMAK omak
#LAST LINE -- ADD YOUR ENTRIES BEFORE THIS ONE -- DO NOT REMOVE
Actions File
#ACTION
Mirrors #Accept traffic from the Shorewall Mirror sites
#LAST LINE - ADD YOUR ENTRIES ABOVE THIS ONE - DO NOT REMOVE
action.Mirrors File
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->dmz traffic needs to
traverse.
#TARGET SOURCE DEST PROTO DEST SOURCE ORIGINAL RATE
# PORT PORT(S) DEST LIMIT
ACCEPT $MIRRORS
#LAST LINE -- ADD YOUR ENTRIES BEFORE THIS ONE -- DO NOT REMOVE
/etc/shorewall/action.Drop
This is my common action for the DROP policy. It is like the
standard Drop action except that it
allows Ping
.
#TARGET SOURCE DEST PROTO DEST SOURCE RATE USER/
# PORT(S) PORT(S) LIMIT GROUP
RejectAuth
AllowPing
dropBcast
DropSMB
DropUPnP
dropNotSyn
DropDNSrep
/etc/shorewall/action.Reject
This is my common action for the REJECT policy. It is like the
standard Reject action except that it
allows Ping
and contains one rule that guards against
log flooding by broken software running in my local zone.
#TARGET SOURCE DEST PROTO DEST SOURCE RATE USER/
# PORT(S) PORT(S) LIMIT GROUP
RejectAuth
AllowPing
dropBcast
RejectSMB
DropUPnP
dropNotSyn
DropDNSrep
DROP loc:eth2:!192.168.1.0/24 #So that my braindead Windows[tm] XP system doesn't flood my log
#with NTP requests with a source address in 16.0.0.0/8 (address of
#its PPTP tunnel to HP).
Rules File (The shell variables are set in
/etc/shorewall/params)
###############################################################################################################################################################################
#RESULT CLIENT(S) SERVER(S) PROTO PORT(S) CLIENT ORIGINAL RATE USER
# PORT(S) DEST:SNAT SET
###############################################################################################################################################################################
# Local Network to Internet - Reject attempts by Trojans to call home, direct SMTP and MS Message Service
#
RejectSMTP loc net tcp 25
REJECT:$LOG loc net tcp 6667,25
REJECT:$LOG loc net udp 1025:1031
#
# Stop NETBIOS crap since our policy is ACCEPT
#
REJECT loc net tcp 137,445
REJECT loc net udp 137:139
#
DROP loc:!192.168.1.0/24 net
#
# SQUID
#
REDIRECT loc 3128 tcp 80
###############################################################################################################################################################################
# Local Network to Firewall
#
DROP loc:!192.168.1.0/24 fw
ACCEPT loc fw tcp ssh,time
ACCEPT loc fw udp 161,ntp
###############################################################################################################################################################################
# Local Network to DMZ
#
DROP loc:!192.168.1.0/24 dmz
ACCEPT loc dmz udp domain,xdmcp
ACCEPT loc dmz tcp www,smtp,smtps,domain,ssh,imap,https,imaps,cvspserver,ftp,10027,pop3 -
###############################################################################################################################################################################
# Internet to ALL -- drop NewNotSyn packets
#
dropNotSyn net fw tcp
dropNotSyn net loc tcp
dropNotSyn net dmz tcp
#
# Drop ping to firewall and local
#
DropPing net fw
DropPing net loc
###############################################################################################################################################################################
# Internet to DMZ
#
DNAT- net dmz:206.124.146.177 tcp smtp - 206.124.146.179,206.124.146.1
78
ACCEPT net dmz tcp smtp,smtps,www,ftp,imaps,domain,https,cvspserver -
ACCEPT net dmz udp domain
ACCEPT net dmz udp 33434:33436
Mirrors net dmz tcp rsync
ACCEPT net:$OMAK dmz tcp 22 #SSH from Omak
AllowPing net dmz
###############################################################################################################################################################################
#
# Net to Local
#
# When I'm "on the road", the following two rules allow me VPN access back home.
#
DNAT net loc:192.168.1.4 tcp 1723 -
DNAT net:!$TEXAS loc:192.168.1.4 gre -
ACCEPT net loc:192.168.1.5 tcp 22
#
# ICQ
#
ACCEPT net loc:192.168.1.5 tcp 4000:4100
DNAT net loc:192.168.1.8 tcp 4000:4100 - 206.124.146.179
#
# Real Audio
#
ACCEPT net loc:192.168.1.5 udp 6970:7170
#
# Overnet
#
#ACCEPT net loc:192.168.1.5 tcp 4662
#ACCEPT net loc:192.168.1.5 udp 12112
#
# Silently Handle common probes
#
REJECT net loc tcp www,ftp,https
###############################################################################################################################################################################
# DMZ to Internet
#
ACCEPT dmz net tcp smtp,domain,www,81,https,whois,echo,2702,21,2703,ssh,8080
ACCEPT dmz net udp domain
REJECT:$LOG dmz net udp 1025:1031
ACCEPT dmz net:$POPSERVERS tcp pop3
#
# Something is wrong with the FTP connection tracking code or there is some client out there
# that is sending a PORT command which that code doesn't understand. Either way,
# the following works around the problem.
#
ACCEPT:$LOG dmz net tcp 1024: 20
###############################################################################################################################################################################
# DMZ to Firewall -- ntp & snmp, Silently reject Auth
#
ACCEPT dmz fw udp ntp ntp
ACCEPT dmz fw tcp 161,ssh
ACCEPT dmz fw udp 161
REJECT dmz fw tcp auth
###############################################################################################################################################################################
# DMZ to Local Network
#
ACCEPT dmz loc tcp smtp,6001:6010
ACCEPT dmz:206.124.146.177 loc:192.168.1.5 tcp 111
ACCEPT dmz:206.124.146.177 loc:192.168.1.5 udp
###############################################################################################################################################################################
# Internet to Firewall
#
REJECT net fw tcp www,ftp,https
ACCEPT net dmz udp 33434:33435
ACCEPT net:$OMAK fw udp ntp
ACCEPT net:$OMAK fw tcp 22 #SSH from Omak
###############################################################################################################################################################################
# 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
REJECT:$LOG fw net udp 1025:1031
DROP fw net udp ntp
###############################################################################################################################################################################
# Firewall to DMZ
#
ACCEPT fw dmz tcp www,ftp,ssh,smtp
ACCEPT fw dmz udp domain
REJECT fw dmz udp 137:139
###############################################################################################################################################################################
ACCEPT tx loc:192.168.1.5 all
#LAST LINE -- ADD YOUR ENTRIES BEFORE THIS ONE -- DO NOT REMOVE
Bridge (Ursa) Configuration
As mentioned above, Ursa acts as a bridge. It's view of the network
is diagrammed in the following figure.
![]()
I've included the files that I used to configure that system -- some
of them are SuSE-specific.
The configuration on Wookie can be modified to test various bridging
features -- otherwise, it serves to isolate the Wireless network from the
rest of our systems.
shorewall.conf
Only the changes from the defaults are shown.
BRIDGING=Yes
zones
#ZONE DISPLAY COMMENTS
loc Local Local networks
net Internet The Big Bad Internet
WiFi Wireless Wireless Network
#LAST LINE - ADD YOUR ENTRIES ABOVE THIS ONE - DO NOT REMOVE
policy
#SOURCE DEST POLICY LOG LIMIT:BURST
loc fw ACCEPT
loc net NONE
loc WiFi ACCEPT
net fw ACCEPT
net WiFi ACCEPT
net loc NONE
WiFi net ACCEPT
fw all ACCEPT
#
# THE FOLLOWING POLICY MUST BE LAST
#
all all REJECT info
#LAST LINE -- DO NOT REMOVE
interfaces
#ZONE INTERFACE BROADCAST OPTIONS
- br0 192.168.1.255 dhcp
#LAST LINE -- ADD YOUR ENTRIES BEFORE THIS ONE -- DO NOT REMOVE
hosts
#ZONE HOST(S) OPTIONS
loc br0:eth1:192.168.1.0/24
net br0:eth1
WiFi br0:eth0 maclist
#LAST LINE -- ADD YOUR ENTRIES BEFORE THIS LINE -- DO NOT REMOVE
rules
#ACTION SOURCE DEST PROTO DEST SOURCE ORIGINAL
# PORT PORT(S) DEST
ACCEPT WiFi loc udp 137:139
ACCEPT WiFi loc tcp 22,80,137,139,445,631,901,3389
ACCEPT WiFi loc udp 1024: 137
ACCEPT WiFi loc udp 177,123
ACCEPT WiFi loc:192.168.1.4 tcp 1723
ACCEPT WiFi loc:192.168.1.4 47
ACCEPT WiFi loc tcp 5900:5909
ACCEPT WiFi fw tcp ssh,80,111,137,139,445,9100:9104
ACCEPT WiFi fw udp
#LAST LINE -- ADD YOUR ENTRIES BEFORE THIS ONE -- DO NOT REMOVE
routestopped
#INTERFACE HOST(S) OPTIONS
br0 0.0.0.0/0 routeback
#LAST LINE -- ADD YOUR ENTRIES BEFORE THIS ONE -- DO NOT REMOVE
maclist
#INTERFACE MAC IP ADDRESSES (Optional)
br0:eth0 00:A0:1C:DB:0C:A0 192.168.1.7 #Work Laptop
br0:eth0 00:04:59:0e:85:b9 #WAP11
br0:eth0 00:06:D5:45:33:3c #WET11
br0:eth0 00:0b:c1:53:cc:97 192.168.1.8 #TIPPER
#LAST LINE -- ADD YOUR ENTRIES ABOVE THIS LINE -- DO NOT REMOVE
/etc/init.d/bridge
This file is SuSE-specific and creates the bridge device
br0. A script for other
disbributions would be similar.
#!/bin/sh
################################################################################
# Script to create a bridge between eth0, eth1 and eth2
#
# This program is under GPL [http://www.gnu.org/copyleft/gpl.htm]
#
# (c) 2004 - Tom Eastep (teastep@shorewall.net)
#
# Modify the following variables to match your configuration
#
# chkconfig: 2345 05 89
# description: Layer 2 Bridge
#
################################################################################
PATH=$PATH:/sbin:/usr/sbin:/usr/local/sbin
do_stop() {
echo "Stopping Bridge"
brctl delbr br0
ip link set eth0 down
ip link set eth1 down
}
do_start() {
echo "Starting Bridge"
ip link set eth0 up
ip link set eth1 up
brctl addbr br0
brctl addif br0 eth0
brctl addif br0 eth1
}
case "$1" in
start)
do_start
;;
stop)
do_stop
;;
restart)
do_stop
sleep 1
do_start
;;
*)
echo "Usage: $0 {start|stop|restart}"
exit 1
esac
exit 0
/etc/sysconfig/network/ifcfg-br0
This file is SuSE-specific
BOOTPROTO='static'
BROADCAST='192.168.1.255'
IPADDR='192.168.1.5'
NETWORK='192.168.1.0'
NETMASK='255.255.255.0'
REMOTE_IPADDR=''
STARTMODE='onboot'
UNIQUE='3hqH.MjuOqWfSZ+C'
WIRELESS='no'
MTU=''
/etc/sysconfig/network/routes
This file is SuSE-specific
192.168.1.0 - 255.255.255.0 br0
default 192.168.1.254 - -