Need help setting up 2nd NIC for DHCPd

[ahab]

Hi there,

on a Linux Redhat 7.3 system, I have to network cards installed. The first is (eth0) is connected to the internet via a static IP address, and I would like to make the second one (eth1) available to other computers using a DHCP server, so that they can access the internet via a router.The other computers are Windows computers.
I basically followed the protocol available on http://www.tldp.org/HOWTO/DHCP/x369.html, that is:

introduced 255.255.255.255 all-ones in /etc/hosts
and then copied the sample dhcpd.conf file in /usr/share/doc/dhcp-3.0pl1/dhcpd.conf.sample over to /etc/dhcpd.conf, however I did not do any modifications on it.
Following this, I started the server: /usr/sbin/dhcpd eth1
and included the same command in the startup file /etc/rc.local to make it available during next boot up.
Now the Windows machine has been setup for DHCP, and it gets an IP address assigned, however I cannot connect to the internet. A lease file has been created on the Linux machine in /var/lib/dhcp/dhcpd.leases, which reads the following:

more /var/lib/dhcp/dhcpd.leases
# All times in this file are in UTC (GMT), not your local timezone. This is
# not a bug, so please don't ask about it. There is no portable way to
# store leases in the local timezone, so please don't request this as a
# feature. If this is inconvenient or confusing to you, we sincerely
# apologize. Seriously, though - don't ask.
# The format of this file is documented in the dhcpd.leases(5) manual page.
# This lease file was written by isc-dhcp-V3.0pl1

lease 192.168.0.255 {
starts 4 2006/03/02 17:19:45;
ends 4 2006/03/02 23:19:45;
tstp 4 2006/03/02 23:19:45;
binding state active;
next binding state free;
hardware ethernet 00:0f:1f:c5:09:3a;
uid "\001\000\017\037\305\011:";
client-hostname "BP-CUFF";

I Windows, I get the following entry in the Network connections --> Support tab:
Address type: Assigned by DHCP
IP Address: 192.168.0.255
Subnet Mask: 255.255.255.0
Default Gateway: 192.168.0.1


What am I doing wrong? May there some adaptations to be done in the /etc/dhcpd.conf file, which I have not done?

Thank you very much in advance for any help solving the problem.

PS: Here is the /etc/dhcpd.conf file:


ddns-update-style interim;
ignore client-updates;

subnet 192.168.0.0 netmask 255.255.255.0 {

# --- default gateway
option routers 192.168.0.1;
option subnet-mask 255.255.255.0;

option nis-domain "domain.org";
option domain-name "domain.org";
option domain-name-servers 192.168.1.1;

option time-offset -18000; # Eastern Standard Time
# option ntp-servers 192.168.1.1;
# option netbios-name-servers 192.168.1.1;
# --- Selects point-to-point node (default is hybrid). Don't change this unless
# -- you understand Netbios very well
# option netbios-node-type 2;

range dynamic-bootp 192.168.0.128 192.168.0.255;
default-lease-time 21600;
max-lease-time 43200;

# we want the nameserver to appear at a fixed address
host ns {
next-server marvin.redhat.com;
hardware ethernet 12:34:56:78:AB:CD;
fixed-address 207.175.42.254;
}
}

[kode]

If I read your post correctly you want to do two things:

1) Make DHCP available on eth1 for your LAN machines
2) Make the DHCP server an internet gateway for those machines

It appears that you have accomplished item #1, since your Windows machine has an IP.

Part 2 has nothing to do with DHCPd -- it require ipchains/iptables -- a masquarading firewall script.

http://www.netfilter.org/ is the authoritative site for such things.

[ahab]

Dear Kode,
I tried to enable the masquerading / forwarding, mainly following the protocol on http://www.tldp.org/HOWTO/IP-Masquer...piling3.1.html, that is in short:

created the file etc/rc.d/rc.firewall-iptables for setting the rules:

#!/bin/sh
#
# rc.firewall-iptables
FWVER=0.76
#
# Initial SIMPLE IP Masquerade test for 2.6 / 2.4 kernels
# using IPTABLES.
#
# Once IP Masquerading has been tested, with this simple
# ruleset, it is highly recommended to use a stronger
# IPTABLES ruleset either given later in this HOWTO or
# from another reputable resource.
#
#
#
# Log:
# 0.76 - Added comments on why the default policy is ACCEPT
# 0.75 - Added more kernel modules to the comments section
# 0.74 - the ruleset now uses modprobe vs. insmod
# 0.73 - REJECT is not a legal policy yet; back to DROP
# 0.72 - Changed the default block behavior to REJECT not DROP
# 0.71 - Added clarification that PPPoE users need to use
# "ppp0" instead of "eth0" for their external interface
# 0.70 - Added commented option for IRC nat module
# - Added additional use of environment variables
# - Added additional formatting
# 0.63 - Added support for the IRC IPTABLES module
# 0.62 - Fixed a typo on the MASQ enable line that used eth0
# instead of $EXTIF
# 0.61 - Changed the firewall to use variables for the internal
# and external interfaces.
# 0.60 - 0.50 had a mistake where the ruleset had a rule to DROP
# all forwarded packets but it didn't have a rule to ACCEPT
# any packets to be forwarded either
# - Load the ip_nat_ftp and ip_conntrack_ftp modules by default
# 0.50 - Initial draft
#

echo -e "\n\nLoading simple rc.firewall-iptables version $FWVER..\n"


# The location of the iptables and kernel module programs
#
# If your Linux distribution came with a copy of iptables,
# most likely all the programs will be located in /sbin. If
# you manually compiled iptables, the default location will
# be in /usr/local/sbin
#
# ** Please use the "whereis iptables" command to figure out
# ** where your copy is and change the path below to reflect
# ** your setup
#
IPTABLES=/sbin/iptables
#IPTABLES=/usr/local/sbin/iptables
DEPMOD=/sbin/depmod
MODPROBE=/sbin/modprobe


#Setting the EXTERNAL and INTERNAL interfaces for the network
#
# Each IP Masquerade network needs to have at least one
# external and one internal network. The external network
# is where the natting will occur and the internal network
# should preferably be addressed with a RFC1918 private address
# scheme.
#
# For this example, "eth0" is external and "eth1" is internal"
#
#
# NOTE: If this doesnt EXACTLY fit your configuration, you must
# change the EXTIF or INTIF variables above. For example:
#
# If you are a PPPoE or analog modem user:
#
# EXTIF="ppp0"
#
#
EXTIF="eth0"
INTIF="eth1"
echo " External Interface: $EXTIF"
echo " Internal Interface: $INTIF"


#================================================= =====================
#== No editing beyond this line is required for initial MASQ testing ==


echo -en " loading modules: "

# Need to verify that all modules have all required dependencies
#
echo " - Verifying that all kernel modules are ok"
$DEPMOD -a

# With the new IPTABLES code, the core MASQ functionality is now either
# modular or compiled into the kernel. This HOWTO shows ALL IPTABLES
# options as MODULES. If your kernel is compiled correctly, there is
# NO need to load the kernel modules manually.
#
# NOTE: The following items are listed ONLY for informational reasons.
# There is no reason to manual load these modules unless your
# kernel is either mis-configured or you intentionally disabled
# the kernel module autoloader.
#

# Upon the commands of starting up IP Masq on the server, the
# following kernel modules will be automatically loaded:
#
# NOTE: Only load the IP MASQ modules you need. All current IP MASQ
# modules are shown below but are commented out from loading.
# ================================================== =============

echo "----------------------------------------------------------------------"

#Load the main body of the IPTABLES module - "iptable"
# - Loaded automatically when the "iptables" command is invoked
#
# - Loaded manually to clean up kernel auto-loading timing issues
#
echo -en "ip_tables, "
$MODPROBE ip_tables


#Load the IPTABLES filtering module - "iptable_filter"
# - Loaded automatically when filter policies are activated


#Load the stateful connection tracking framework - "ip_conntrack"
#
# The conntrack module in itself does nothing without other specific
# conntrack modules being loaded afterwards such as the "ip_conntrack_ftp"
# module
#
# - This module is loaded automatically when MASQ functionality is
# enabled
#
# - Loaded manually to clean up kernel auto-loading timing issues
#
echo -en "ip_conntrack, "
$MODPROBE ip_conntrack


#Load the FTP tracking mechanism for full FTP tracking
#
# Enabled by default -- insert a "#" on the next line to deactivate
#
echo -en "ip_conntrack_ftp, "
$MODPROBE ip_conntrack_ftp


#Load the IRC tracking mechanism for full IRC tracking
#
# Enabled by default -- insert a "#" on the next line to deactivate
#
echo -en "ip_conntrack_irc, "
$MODPROBE ip_conntrack_irc


#Load the general IPTABLES NAT code - "iptable_nat"
# - Loaded automatically when MASQ functionality is turned on
#
# - Loaded manually to clean up kernel auto-loading timing issues
#
echo -en "iptable_nat, "
$MODPROBE iptable_nat


#Loads the FTP NAT functionality into the core IPTABLES code
# Required to support non-PASV FTP.
#
# Enabled by default -- insert a "#" on the next line to deactivate
#
echo -en "ip_nat_ftp, "
$MODPROBE ip_nat_ftp


#Loads the IRC NAT functionality into the core IPTABLES code
# Required to support NAT of IRC DCC requests
#
# Disabled by default -- remove the "#" on the next line to activate
#
#echo -e "ip_nat_irc"
#$MODPROBE ip_nat_irc

echo "----------------------------------------------------------------------"

# Just to be complete, here is a partial list of some of the other
# IPTABLES kernel modules and their function. Please note that most
# of these modules (the ipt ones) are automatically loaded by the
# master kernel module for proper operation and don't need to be
# manually loaded.
# --------------------------------------------------------------------
#
# ip_nat_snmp_basic - this module allows for proper NATing of some
# SNMP traffic
#
# iptable_mangle - this target allows for packets to be
# manipulated for things like the TCPMSS
# option, etc.
#
# --
#
# ipt_mark - this target marks a given packet for future action.
# This automatically loads the ipt_MARK module
#
# ipt_tcpmss - this target allows to manipulate the TCP MSS
# option for braindead remote firewalls.
# This automatically loads the ipt_TCPMSS module
#
# ipt_limit - this target allows for packets to be limited to
# to many hits per sec/min/hr
#
# ipt_multiport - this match allows for targets within a range
# of port numbers vs. listing each port individually
#
# ipt_state - this match allows to catch packets with various
# IP and TCP flags set/unset
#
# ipt_unclean - this match allows to catch packets that have invalid
# IP/TCP flags set
#
# iptable_filter - this module allows for packets to be DROPped,
# REJECTed, or LOGged. This module automatically
# loads the following modules:
#
# ipt_LOG - this target allows for packets to be
# logged
#
# ipt_REJECT - this target DROPs the packet and returns
# a configurable ICMP packet back to the
# sender.
#

echo -e " Done loading modules.\n"



#CRITICAL: Enable IP forwarding since it is disabled by default since
#
# Redhat Users: you may try changing the options in
# /etc/sysconfig/network from:
#
# FORWARD_IPV4=false
# to
# FORWARD_IPV4=true
#
echo " Enabling forwarding.."
echo "1" > /proc/sys/net/ipv4/ip_forward


# Dynamic IP users:
#
# If you get your IP address dynamically from SLIP, PPP, or DHCP,
# enable this following option. This enables dynamic-address hacking
# which makes the life with Diald and similar programs much easier.
#
#echo " Enabling DynamicAddr.."
#echo "1" > /proc/sys/net/ipv4/ip_dynaddr


# Enable simple IP forwarding and Masquerading
#
# NOTE: In IPTABLES speak, IP Masquerading is a form of SourceNAT or SNAT.
#
# NOTE #2: The following is an example for an internal LAN address in the
# 192.168.0.x network with a 255.255.255.0 or a "24" bit subnet mask
# connecting to the Internet on external interface "eth0". This
# example will MASQ internal traffic out to the Internet but not
# allow non-initiated traffic into your internal network.

[ahab]

#
#
# ** Please change the above network numbers, subnet mask, and your
# *** Internet connection interface name to match your setup
#


#Clearing any previous configuration
#
# Unless specified, the defaults for INPUT and OUTPUT is ACCEPT
# The default for FORWARD is DROP (REJECT is not a valid policy)
#
# Isn't ACCEPT insecure? To some degree, YES, but this is our testing
# phase. Once we know that IPMASQ is working well, I recommend you run
# the rc.firewall-*-stronger rulesets which set the defaults to DROP but
# also include the critical additional rulesets to still let you connect to
# the IPMASQ server, etc.
#
echo " Clearing any existing rules and setting default policy.."
$IPTABLES -P INPUT ACCEPT
$IPTABLES -F INPUT
$IPTABLES -P OUTPUT ACCEPT
$IPTABLES -F OUTPUT
$IPTABLES -P FORWARD DROP
$IPTABLES -F FORWARD
$IPTABLES -t nat -F

echo " FWD: Allow all connections OUT and only existing and related ones IN"
$IPTABLES -A FORWARD -i $EXTIF -o $INTIF -m state --state ESTABLISHED,RELATED -j ACCEPT
$IPTABLES -A FORWARD -i $INTIF -o $EXTIF -j ACCEPT
$IPTABLES -A FORWARD -j LOG

echo " Enabling SNAT (MASQUERADE) functionality on $EXTIF"
$IPTABLES -t nat -A POSTROUTING -o $EXTIF -j MASQUERADE

echo -e "\nrc.firewall-iptables v$FWVER done.\n"

Then, I created /etc/rc.d/init.d/firewall-iptables to start the masquerading during boot time:
#!/bin/sh
#
# chkconfig: 2345 11 89
#
# description: Loads the rc.firewall-iptables ruleset.
#
# processname: firewall-iptables
# pidfile: /var/run/firewall.pid
# config: /etc/rc.d/rc.firewall-iptables
# probe: true

# ----------------------------------------------------------------------------
# v05/24/03
#
# Part of the copyrighted and trademarked TrinityOS document.
# http://www.ecst.csuchico.edu/~dranch
#
# Written and Maintained by David A. Ranch
# dranch@trinnet.net
#
# Updates
# -------
# 05/24/03 - removed a old networking up check that had some
# improper SGML ampersand conversions.
# ----------------------------------------------------------------------------


# Source function library.
. /etc/rc.d/init.d/functions

# Check that networking is up.

[ "XXXX${NETWORKING}" = "XXXXno" ] && exit 0

[ -x /sbin/ifconfig ] || exit 0

# The location of various iptables and other shell programs
#
# If your Linux distribution came with a copy of iptables, most
# likely it is located in /sbin. If you manually compiled
# iptables, the default location is in /usr/local/sbin
#
# ** Please use the "whereis iptables" command to figure out
# ** where your copy is and change the path below to reflect
# ** your setup
#
IPTABLES=/usr/local/sbin/iptables


# See how we were called.
case "$1" in
start)
/etc/rc.d/rc.firewall-iptables
;;

stop)
echo -e "\nFlushing firewall and setting default policies to DROP\n"
$IPTABLES -P INPUT DROP
$IPTABLES -F INPUT
$IPTABLES -P OUTPUT DROP
$IPTABLES -F OUTPUT
$IPTABLES -P FORWARD DROP
$IPTABLES -F FORWARD
$IPTABLES -F -t nat

# Delete all User-specified chains
$IPTABLES -X
#
# Reset all IPTABLES counters
$IPTABLES -Z
;;

restart)
$0 stop
$0 start
;;

status)
$IPTABLES -L
;;

mlist)
cat /proc/net/ip_conntrack
;;

*)
echo "Usage: firewall-iptables {start|stop|status|mlist}"
exit 1
esac

exit 0

then, made this script execuctable:
chmod 700 /etc/rc.d/init.d/firewall-iptables

[ahab]

after reboot, I checked:
chkconfig --list firewall-iptables, and I got a response exactly as indicated on the protocol.

Unfortunately, it still does not work to access the internet from an internal machine (connected to eth1 via DHCP). I cannot even ping the DHCP server on the IP address on eth1.

ls /proc/sys/net/ipv4 returns:

conf ip_autoconfig neigh tcp_keepalive_time tcp_rmem
icmp_echo_ignore_all ip_conntrack_max route tcp_low_latency tcp_sack
icmp_echo_ignore_broadcasts ip_default_ttl tcp_abort_on_overflow tcp_max_orphans tcp_stdurg
icmp_ignore_bogus_error_responses ip_dynaddr tcp_adv_win_scale tcp_max_syn_backlog tcp_synack_retries
icmp_ratelimit ip_forward tcp_app_win tcp_max_tw_buckets tcp_syncookies
icmp_ratemask ipfrag_high_thresh tcp_dsack tcp_mem tcp_syn_retries
igmp_max_memberships ipfrag_low_thresh tcp_ecn tcp_orphan_retries tcp_timestamps
inet_peer_gc_maxtime ipfrag_secret_interval tcp_fack tcp_reordering tcp_tw_recycle
inet_peer_gc_mintime ipfrag_time tcp_fin_timeout tcp_retrans_collapse tcp_tw_reuse
inet_peer_maxttl ip_local_port_range tcp_frto tcp_retries1 tcp_window_scaling
inet_peer_minttl ip_nonlocal_bind tcp_keepalive_intvl tcp_retries2 tcp_wmem
inet_peer_threshold ip_no_pmtu_disc tcp_keepalive_probes tcp_rfc1337

/sbin/lsmod returns:

Module Size Used by Tainted: P
sr_mod 16632 0 (autoclean)
i810_audio 25504 0 (autoclean)
ac97_codec 13280 0 (autoclean) [i810_audio]
soundcore 6468 2 (autoclean) [i810_audio]
nvidia 4018092 6
nfsd 76960 8 (autoclean)
lockd 57088 1 (autoclean) [nfsd]
sunrpc 76916 1 (autoclean) [nfsd lockd]
autofs 11844 0 (autoclean) (unused)
ipt_MASQUERADE 2368 1 (autoclean)
ipt_LOG 4448 1 (autoclean)
ipt_state 1344 1 (autoclean)
iptable_filter 2560 1 (autoclean)
ip_nat_ftp 4064 0 (unused)
iptable_nat 22228 2 [ipt_MASQUERADE ip_nat_ftp]
ip_conntrack_irc 4352 0 (unused)
ip_conntrack_ftp 5120 1
ip_conntrack 26228 4 [ipt_MASQUERADE ipt_state ip_nat_ftp iptable_nat ip_conntrack_irc ip_conntrack_ftp]
ip_tables 13952 7 [ipt_MASQUERADE ipt_LOG ipt_state iptable_filter iptable_nat]
tg3 45664 1
eepro100 21068 1
mii 3976 0 [eepro100]
ide-scsi 11008 0
ide-cd 32256 0
cdrom 32128 0 [sr_mod ide-cd]
sd_mod 12892 0 (autoclean) (unused)
scsi_mod 107596 3 (autoclean) [sr_mod ide-scsi sd_mod]
reiserfs 190752 0 (autoclean)
mousedev 5152 1
hid 20992 0 (unused)
input 5760 0 [mousedev hid]
ehci-hcd 18368 0 (unused)
usb-uhci 24708 0 (unused)
usbcore 73792 1 [hid ehci-hcd usb-uhci]
ext3 65952 3
jbd 47564 3 [ext3]

and ls /proc/net/
arp dev_mcast ip_conntrack ip_tables_names packet route rt_cache sockstat tr_rif wireless
atm drivers ip_mr_cache netlink psched rpc rt_cache_stat softnet_stat udp
dev igmp ip_mr_vif netstat raw rt_acct snmp tcp unix

and finally ls /lib/modules/`uname -r`/kernel/net/ipv4/netfilter/ gives:
arptable_filter.o ip_conntrack_tftp.o ip_queue.o ipt_dscp.o ipt_limit.o ipt_multiport.o ipt_TCPMSS.o
arp_tables.o ipfwadm.o iptable_filter.o ipt_DSCP.o ipt_LOG.o ipt_owner.o ipt_tos.o
ipchains.o ip_nat_amanda.o iptable_mangle.o ipt_ecn.o ipt_mac.o ipt_pkttype.o ipt_TOS.o
ip_conntrack_amanda.o ip_nat_ftp.o iptable_nat.o ipt_ECN.o ipt_mark.o ipt_REDIRECT.o ipt_ttl.o
ip_conntrack_ftp.o ip_nat_irc.o ip_tables.o ipt_esp.o ipt_MARK.o ipt_REJECT.o ipt_ULOG.o
ip_conntrack_irc.o ip_nat_snmp_basic.o ipt_ah.o ipt_helper.o ipt_MASQUERADE.o ipt_state.o ipt_unclean.o
ip_conntrack.o ip_nat_tftp.o ipt_conntrack.o ipt_length.o ipt_MIRROR.o ipt_tcpmss.o

What am I doing wrong? do I miss a module? I feel being really close to the solution, but cannot see the trees in the forest!

Any help is greatly appreciated!
Thanks,

Ahab