問題があります。Windows 7 クライアントからイーサネット接続された MFP にアクセスできませんが、Ubuntu (およびルーター/サーバー) マシンからはアクセスできます。
MFP = エプソン スタイラス カラー 730
通信網：
MFP (192.168.0.100) + win7clients (192.168.0.101-200) ---> Ubuntu サーバー/ルーター (192.168.0.1) ---> インターネット
MFP は DHCP サーバーから適切な IP と設定を取得します。Windows マシンでは、すべてのファイアウォールなどを無効にしました。
Ubuntu からは MFP でやりたいことを実行できますが、なぜ Windows から ping を実行することさえできないのでしょうか?
ありがとう
編集：
/etc/sysctl.confの内容:
#
# /etc/sysctl.conf - Configuration file for setting system variables
# See /etc/sysctl.d/ for additional system variables
# See sysctl.conf (5) for information.
#
#kernel.domainname = example.com
# Uncomment the following to stop low-level messages on console
#kernel.printk = 3 4 1 3
##############################################################3
# Functions previously found in netbase
#
# Uncomment the next two lines to enable Spoof protection (reverse-path filter)
# Turn on Source Address Verification in all interfaces to
# prevent some spoofing attacks
#net.ipv4.conf.default.rp_filter=1
#net.ipv4.conf.all.rp_filter=1
# Uncomment the next line to enable TCP/IP SYN cookies
# See http://lwn.net/Articles/277146/
# Note: This may impact IPv6 TCP sessions too
#net.ipv4.tcp_syncookies=1
# Uncomment the next line to enable packet forwarding for IPv4
net.ipv4.ip_forward=1
# Uncomment the next line to enable packet forwarding for IPv6
# Enabling this option disables Stateless Address Autoconfiguration
# based on Router Advertisements for this host
#net.ipv6.conf.all.forwarding=1
###################################################################
# Additional settings - these settings can improve the network
# security of the host and prevent against some network attacks
# including spoofing attacks and man in the middle attacks through
# redirection. Some network environments, however, require that these
# settings are disabled so review and enable them as needed.
#
# Do not accept ICMP redirects (prevent MITM attacks)
#net.ipv4.conf.all.accept_redirects = 0
#net.ipv6.conf.all.accept_redirects = 0
# _or_
# Accept ICMP redirects only for gateways listed in our default
# gateway list (enabled by default)
# net.ipv4.conf.all.secure_redirects = 1
#
# Do not send ICMP redirects (we are not a router)
#net.ipv4.conf.all.send_redirects = 0
#
# Do not accept IP source route packets (we are not a router)
#net.ipv4.conf.all.accept_source_route = 0
#net.ipv6.conf.all.accept_source_route = 0
#
# Log Martian Packets
#net.ipv4.conf.all.log_martians = 1
#
編集 2: いくつかの修正後 - ローカル ネットの私を除くすべてが MFP を使用できます。だから、新しいパズル：
私のローカルネットワーク: http://prntscr.com/kvk5g
「はくほのお」は複合機が見えませんが、他は見えます。
/etc/iptables.confの内容:
# Generated by iptables-save v1.4.12 on Fri Nov 9 01:51:58 2012
*filter
:INPUT ACCEPT [23:1420]
:FORWARD DROP [0:0]
:OUTPUT ACCEPT [20:18904]
-A INPUT -i lo -j ACCEPT
-A INPUT -i eth0 -m state --state RELATED,ESTABLISHED -j ACCEPT
-A INPUT -d 224.0.0.0/4 -i eth0 -j ACCEPT
-A INPUT -s 224.0.0.0/4 -i eth0 -j ACCEPT
-A INPUT -i eth0 -p tcp -m tcp --dport 80:85 -j ACCEPT
-A INPUT -i eth0 -p tcp -m tcp --dport 1985 -j ACCEPT
-A INPUT -i eth0 -p tcp -m tcp --dport 25565 -j ACCEPT
-A INPUT -i eth0 -p tcp -m state --state NEW -m tcp --dport 60000:65000 -j ACCEPT
-A INPUT -i eth0 -j DROP
-A FORWARD -i eth0 -o br0 -m conntrack --ctstate RELATED,ESTABLISHED -j ACCEPT
-A FORWARD -i br0 -o eth0 -j ACCEPT
-A FORWARD -d 224.0.0.0/4 -j ACCEPT
-A FORWARD -s 224.0.0.0/4 -j ACCEPT
-A FORWARD -i eth0 -p tcp --dport 81:85 -j ACCEPT
-A FORWARD -i eth0 -j DROP
COMMIT
# Completed on Fri Nov 9 01:51:58 2012
# Generated by iptables-save v1.4.12 on Fri Nov 9 01:51:58 2012
*nat
:PREROUTING ACCEPT [377:31747]
:INPUT ACCEPT [39:3558]
:OUTPUT ACCEPT [11:872]
:POSTROUTING ACCEPT [7:570]
-A PREROUTING -i eth0 -p tcp --dport 81:85 -j DNAT --to 192.168.0.101
-A POSTROUTING -o eth0 -j MASQUERADE
COMMIT
# Completed on Fri Nov 9 01:51:58 2012
# Generated by iptables-save v1.4.12 on Fri Nov 9 01:51:58 2012
*mangle
:PREROUTING ACCEPT [1425:140833]
:INPUT ACCEPT [762:69219]
:FORWARD ACCEPT [495:56655]
:OUTPUT ACCEPT [643:122295]
:POSTROUTING ACCEPT [1152:179096]
-A PREROUTING -d 224.0.0.0/4 -p udp -j TTL --ttl-inc 1
COMMIT
# Completed on Fri Nov 9 01:51:58 2012