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初学FPGA， 怎么从硬件上理解？
来源：互联网 作者：佚名日 14:16
[导读] 先理解组合逻辑和时序逻辑，后面就好说了，这里先讲讲狭义的组合逻辑和时序逻辑，时序逻辑一般指的是D触发器，组合逻辑指的是：与门 或门 非门，比较器，选择器，编码器，译码器，加法器，当然还有两类比较特殊的就是三态门和RAM，时序逻辑D触发器需要时钟来驱动的，也就是必须要有时钟才会 动作，而组合逻辑不需要时钟驱动，在时序图上的表现就是时序逻辑的输出比输入晚一个时钟周期，而组合逻辑输入和输出都是在同一个时钟周期，所有的数字电路 都是由组合逻辑和时序逻辑构成，大到CPU，小到电子表芯片，然后我们看看上面的组合逻辑和时序逻辑怎么来用硬件描述语言来描述。
　　先理解组合逻辑和时序逻辑，后面就好说了，这里先讲讲狭义的组合逻辑和时序逻辑，时序逻辑一般指的是D触发器，组合逻辑指的是：与门 或门 非门，比较器，选择器，编码器，译码器，加法器，当然还有两类比较特殊的就是三态门和RAM，时序逻辑D触发器需要时钟来驱动的，也就是必须要有时钟才会 动作，而组合逻辑不需要时钟驱动，在时序图上的表现就是时序逻辑的输出比输入晚一个时钟周期，而组合逻辑输入和输出都是在同一个时钟周期，所有的数字电路 都是由组合逻辑和时序逻辑构成，大到CPU，小到电子表芯片，然后我们看看上面的组合逻辑和时序逻辑怎么来用硬件描述语言来描述。
　　1：与门
　　assign c = a&b；
　　always@（*）
　　2：或门
　　assign c = a|b；
　　always@（*）
　　3：非门
　　assign c = ~a；
　　always@（*）
　　4：比较器
　　assign c = （a》=b）？1&b1:1&b0；
　　always@（*）
　　if（a》=b）
　　c=1&b1;
　　c=1&b0;
　　5：选择器
　　assign c = （a》=b）？d:e；
　　always@（*）
　　if（a》=b）
　　6：译码器
　　always@（*）
　　case（a）
　　2&b0;c=4&b0001;
　　2&b1;c=4&b0010;
　　2&b2;c=4&b0010;
　　2&b3;c=4&b1000;
　　endcase
　　7：编码器
　　always@（*）
　　case（a）
　　4&b0001 ：c=2&d0;
　　4&b0010 ：c=2&d1;
　　4&b0010 ：c=2&d2;
　　4&b1000; c=2&d3;
　　endcase
　　8：加法器
　　assign c= a+b；
　　时序逻辑D触发器
　　alway@（posedge clk or negedge rst_n）
　　if（rst_n==1&b0）
　　q《=1&b0;
　　q 《=d;
　　描 述完成上面的这些，我基本上可以用上面这些标准的电路和语言描述出90%的数字电路了，先从最简单的计数器开始吧，计数器在常见不过，我们先写一个模10 的计数器，省去模块端口定义和信号定位，以下就是核心代码了，为了让LZ可以看清楚具体的电路，可能刚刚看着代码LZ可能会有些难懂，不过没有关系，要学 会硬件的思维这个是必经之路
　　我 们可以看到一个简单的模10计数器实际上是由4部分组成，一个比较器，一个加法器，一个选择器，和4个D触发器，所以一个计数器实际上是由上面最初介绍的 那几个基本单元组成，我打开了FPGA神器quartus，综合一些，改正了若干的语法错误，然后最终的综合的RTL电路如下
　　电 路和代码配合的实在是太好了 代码描述了4部分的电路，而电路也表现出来了4部分的电路，我们可以看到 ADDER 加法器，LESS_THAN 比较器，MUX21 选择器 最后一个D触发器，这就是硬件思维，硬件思维就是认为所有的数字电路都是由基本的组合逻辑和时序逻辑的组件组合而成，写出来的代码都有对应的最小的电路组 件来对应，既然代码都写出来代码，那我们就来看看时序图，来验证一下 时序逻辑的输入和输出总是延迟一个时钟周期，组合逻辑的输入和输出在同一个时钟周期，开始搭建testbench，此处省略一万字，熟悉的波形终于出来了
　　可能上面那个也周期内的图不一定看的清，就看第二幅图吧，我们可以看到在
　　这 3行代码是同时执行的，是串行的，在cnt_cnr 》=&d9的那一个时钟周期就执行完成，和C语言的执行方式其实是一样的，但是cnt_cur 的赋值就可以看到虽然是把cnt_nxt 赋值给cnt_cur，但是由于是时序逻辑所以总是要延迟一个时钟周期，好一个最简单的模10计数器就介绍完了，但是是不是所有的计数器都要写的这么复杂 能，不是，还有两种基本的写法，一种写法就是如下，把所有的组合逻辑都写在了一起，
　　还有这种最最常见的写法就是不区分组合逻辑和时序逻辑，所有的都写在一个always块里面，就当成时序逻辑来写，这个只不上是上面两种电路的一种抽象一点的写法，但是基本的组合逻辑和时序逻辑都还是一样
　　不信看看rtl 和上面的一模一样
　　一 个基本的电路都是由基本的组合逻辑电路和D触发器组成，如果不能用着两个来组成，那你可能是弄错了，比方说有新手经常写一个延时电路，能用# 10么，#10可以是由选择器，还是与或非或者是D触发器来组成么，综合器能理解么，明显不行，所以在自己写一个代码的时候一定要想想他最后的电路是什 么，谈完了计数器，这个最最常用的电路，谈完了这个我想在谈谈verilog，对于verilog我的建议是，遇到组合逻辑用阻塞赋值，遇到时序逻辑用非 阻塞赋值，基本的语法就那么几条，
　　always assign if else case ？： 》= 《= == & | ~ && || ！这个几个搞定了，应该所有的电路都可以描述了，其他的什么就不用去理会了，你写RTL是用不着的，乱用反而会用错，什么while ， initial ，这些都是仿真用的，写rtl根本用不到，
　　至于如何上手比较快些，FPGA开发的流程无非就是 ，方案，代码，仿真，后端约束，上板验证，找一个项目吧这个流程都走一我相信上手起来应该不难比如说开发一个简单的UART，这个最常见的模块，或者一个 dds，或者sdram控制器，首先把方案做出来，就是把基本的电路和实现方法画到草稿上面或者电脑上面，考虑多方面，可靠性，可实现性，资源，能不能跑 到要的时钟频率，等等，接口的信号有哪些，时序是什么样子的，内部怎么控制，用状态机还是计数器，状态机的状态转移图是什么样，有哪些状态，状态迁移的条 件有哪些，会不会跑非，等等
如今，物联网浪潮已然席卷至汽车电子产业，发动机控制系统、底盘控制系统和车身电子控制系统已模型初显，安全...
ADAS市场或破千亿
国产汽车雷达将爆发
抢占智能汽车制高点
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.All Rights Reserved11.10 - Everytime i am trying to connect to my box using SSH, its failing not connecting - Ask Ubuntu
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From any other PC doing SSH to my Ubuntu 11.10,is failing.
My network setup:
Telenet ISP (Belgium) > Fiber cable & > RJ45 cable straight > to Ubuntu PC
Even the SSH is running:
Other PC: retrying over and over
$ ping 192.168.0.128
PING 192.168.0.128 (192.168.0.128) 56(84) bytes of data.
From 192.168.0.226 icmp_seq=1 Destination Host Unreachable
From 192.168.0.226 icmp_seq=2 Destination Host Unreachable
From 192.168.0.226 icmp_seq=3 Destination Host Unreachable
From 192.168.0.226 icmp_seq=4 Destination Host Unreachable
$ sudo service iptables stop
Stopping iptables (via systemctl):
$ ssh sun@192.168.0.128
ssh: connect to host 192.168.0.128 port 22: No route to host
$ ssh sun@192.168.0.128
ssh: connect to host 192.168.0.128 port 22: No route to host
$ ssh sun@192.168.0.128
ssh: connect to host 192.168.0.128 port 22: No route to host
$ ssh sun@192.168.0.128
ssh: connect to host 192.168.0.128 port 22: No route to host
$ ssh sun@192.168.0.128
Connection closed by 192.168.0.128
$ ssh sun@192.168.0.128
sun@192.168.0.128's password:
Connection closed by UNKNOWN
$ ssh sun@192.168.0.128
ssh: connect to host 192.168.0.128 port 22: No route to host
$ ssh sun@192.168.0.128
ssh: connect to host 192.168.0.128 port 22: No route to host
Follow up:
-- checked cable
-- using cable tester and other detectors
-- no problem found in cable
-- used random 10 cables
-- adapter is not broken
-- checked it using circuit tester by opening the system
(card is new so its not network adapter card problem)
-- leds are OK showing
-- used LiveCD and did same ping test was having same problem
-- disabled ipv6 100% to make sure its not the cause
-- disabled iptables 100% so its also not the issue
-- some more info
$ nmap 192.168.0.128
Starting Nmap 5.50 ( http://nmap.org ) at
19:11 CEST
Nmap scan report for 192.168.0.128
Host is up (0.00045s latency).
All 1000 scanned ports on 192.168.0.128 are closed (842) or filtered (158)
Nmap done: 1 IP address (1 host up) scanned in 6.86 seconds
ubuntu@ubuntu:~$ netstat -aunt | head
Active Internet connections (servers and established)
Proto Recv-Q Send-Q Local Address
Foreign Address
0 127.0.0.1:631
1 192.168.0.128:58616
74.125.132.99:80
0 192.168.0.128:56749
199.7.57.72:80
ESTABLISHED
1 192.168.0.128:58614
74.125.132.99:80
0 192.168.0.128:49916
173.194.65.113:443
ESTABLISHED
1 192.168.0.128:45699
64.34.119.101:80
0 192.168.0.128:48404
64.34.119.12:80
ESTABLISHED
0 192.168.0.128:54161
67.201.31.70:80
$ sudo killall dnsmasq
-- did not solved the problem --
-- like many other Q/A was suggesting this same ---
$ iptables --list
Chain INPUT (policy ACCEPT)
prot opt source
destination
Chain FORWARD (policy ACCEPT)
prot opt source
destination
Chain OUTPUT (policy ACCEPT)
prot opt source
destination
$ netstat -nr
Kernel IP routing table
Destination
MSS Window
irtt Iface
192.168.0.1
169.254.0.0
255.255.0.0
192.168.0.0
255.255.255.0
$ ssh -vvv sun@192.168.0.128
OpenSSH_5.6p1, OpenSSL 1.0.0j-fips 10 May 2012
debug1: Reading configuration data /etc/ssh/ssh_config
debug1: Applying options for *
debug2: ssh_connect: needpriv 0
debug1: Connecting to 192.168.0.128 [192.168.0.128] port 22.
debug1: Connection established.
debug3: Not a RSA1 key file /home/sun/.ssh/id_rsa.
debug2: key_type_from_name: unknown key type '-----BEGIN'
debug3: key_read: missing keytype
debug3: key_read: missing whitespace
debug3: key_read: missing whitespace
debug3: key_read: missing whitespace
debug3: key_read: missing whitespace
debug3: key_read: missing whitespace
debug3: key_read: missing whitespace
debug3: key_read: missing whitespace
debug3: key_read: missing whitespace
debug3: key_read: missing whitespace
debug3: key_read: missing whitespace
debug3: key_read: missing whitespace
debug3: key_read: missing whitespace
debug3: key_read: missing whitespace
debug3: key_read: missing whitespace
debug3: key_read: missing whitespace
debug3: key_read: missing whitespace
debug3: key_read: missing whitespace
debug3: key_read: missing whitespace
debug3: key_read: missing whitespace
debug3: key_read: missing whitespace
debug3: key_read: missing whitespace
debug3: key_read: missing whitespace
debug3: key_read: missing whitespace
debug3: key_read: missing whitespace
debug3: key_read: missing whitespace
debug2: key_type_from_name: unknown key type '-----END'
debug3: key_read: missing keytype
debug1: identity file /home/sun/.ssh/id_rsa type 1
debug1: identity file /home/sun/.ssh/id_rsa-cert type -1
debug1: identity file /home/sun/.ssh/id_dsa type -1
debug1: identity file /home/sun/.ssh/id_dsa-cert type -1
debug1: Remote protocol version 2.0, remote software version OpenSSH_5.8p1 Debian-7ubuntu1
debug1: match: OpenSSH_5.8p1 Debian-7ubuntu1 pat OpenSSH*
debug1: Enabling compatibility mode for protocol 2.0
debug1: Local version string SSH-2.0-OpenSSH_5.6
debug2: fd 3 setting O_NONBLOCK
debug1: SSH2_MSG_KEXINIT sent
debug1: SSH2_MSG_KEXINIT received
debug2: kex_parse_kexinit: diffie-hellman-group-exchange-sha256,diffie-hellman-group-exchange-sha1,diffie-hellman-group14-sha1,diffie-hellman-group1-sha1
debug2: kex_parse_kexinit: ssh-rsa-cert-,ssh-dss-cert-,ssh-rsa-cert-,ssh-dss-cert-,ssh-rsa,ssh-dss
debug2: kex_parse_kexinit: aes128-ctr,aes192-ctr,aes256-ctr,arcfour256,arcfour128,aes128-cbc,3des-cbc,blowfish-cbc,cast128-cbc,aes192-cbc,aes256-cbc,arcfour,rijndael-cbc@lysator.liu.se
debug2: kex_parse_kexinit: aes128-ctr,aes192-ctr,aes256-ctr,arcfour256,arcfour128,aes128-cbc,3des-cbc,blowfish-cbc,cast128-cbc,aes192-cbc,aes256-cbc,arcfour,rijndael-cbc@lysator.liu.se
debug2: kex_parse_kexinit: hmac-md5,hmac-sha1,umac-,hmac-ripemd160,hmac-,hmac-sha1-96,hmac-md5-96
debug2: kex_parse_kexinit: hmac-md5,hmac-sha1,umac-,hmac-ripemd160,hmac-,hmac-sha1-96,hmac-md5-96
debug2: kex_parse_kexinit: none,,zlib
debug2: kex_parse_kexinit: none,,zlib
debug2: kex_parse_kexinit:
debug2: kex_parse_kexinit:
debug2: kex_parse_kexinit: first_kex_follows 0
debug2: kex_parse_kexinit: reserved 0
debug2: kex_parse_kexinit: ecdh-sha2-nistp256,ecdh-sha2-nistp384,ecdh-sha2-nistp521,diffie-hellman-group-exchange-sha256,diffie-hellman-group-exchange-sha1,diffie-hellman-group14-sha1,diffie-hellman-group1-sha1
debug2: kex_parse_kexinit: ssh-rsa,ssh-dss,ecdsa-sha2-nistp256
debug2: kex_parse_kexinit: aes128-ctr,aes192-ctr,aes256-ctr,arcfour256,arcfour128,aes128-cbc,3des-cbc,blowfish-cbc,cast128-cbc,aes192-cbc,aes256-cbc,arcfour,rijndael-cbc@lysator.liu.se
debug2: kex_parse_kexinit: aes128-ctr,aes192-ctr,aes256-ctr,arcfour256,arcfour128,aes128-cbc,3des-cbc,blowfish-cbc,cast128-cbc,aes192-cbc,aes256-cbc,arcfour,rijndael-cbc@lysator.liu.se
debug2: kex_parse_kexinit: hmac-md5,hmac-sha1,umac-,hmac-ripemd160,hmac-,hmac-sha1-96,hmac-md5-96
debug2: kex_parse_kexinit: hmac-md5,hmac-sha1,umac-,hmac-ripemd160,hmac-,hmac-sha1-96,hmac-md5-96
debug2: kex_parse_kexinit: none,
debug2: kex_parse_kexinit: none,
debug2: kex_parse_kexinit:
debug2: kex_parse_kexinit:
debug2: kex_parse_kexinit: first_kex_follows 0
debug2: kex_parse_kexinit: reserved 0
debug2: mac_setup: found hmac-md5
debug1: kex: server-&client aes128-ctr hmac-md5 none
debug2: mac_setup: found hmac-md5
debug1: kex: client-&server aes128-ctr hmac-md5 none
debug1: SSH2_MSG_KEX_DH_GEX_REQUEST(92) sent
debug1: expecting SSH2_MSG_KEX_DH_GEX_GROUP
debug2: dh_gen_key: priv key bits set: 118/256
debug2: bits set: 539/1024
debug1: SSH2_MSG_KEX_DH_GEX_INIT sent
debug1: expecting SSH2_MSG_KEX_DH_GEX_REPLY
debug3: check_host_in_hostfile: host 192.168.0.128 filename /home/sun/.ssh/known_hosts
debug3: check_host_in_hostfile: host 192.168.0.128 filename /home/sun/.ssh/known_hosts
debug3: check_host_in_hostfile: match line 139
debug1: Host '192.168.0.128' is known and matches the RSA host key.
debug1: Found key in /home/sun/.ssh/known_hosts:139
debug2: bits set: 544/1024
debug1: ssh_rsa_verify: signature correct
debug2: kex_derive_keys
debug2: set_newkeys: mode 1
debug1: SSH2_MSG_NEWKEYS sent
debug1: expecting SSH2_MSG_NEWKEYS
debug2: set_newkeys: mode 0
debug1: SSH2_MSG_NEWKEYS received
debug1: Roaming not allowed by server
debug1: SSH2_MSG_SERVICE_REQUEST sent
debug2: service_accept: ssh-userauth
debug1: SSH2_MSG_SERVICE_ACCEPT received
debug2: key: /home/sun/.ssh/id_rsa (0x213db960)
debug2: key: /home/sun/.ssh/id_dsa ((nil))
debug1: Authentications that can continue: publickey,password
debug3: start over, passed a different list publickey,password
debug3: preferred gssapi-keyex,gssapi-with-mic,publickey,keyboard-interactive,password
debug3: authmethod_lookup publickey
debug3: remaining preferred: keyboard-interactive,password
debug3: authmethod_is_enabled publickey
debug1: Next authentication method: publickey
debug1: Offering RSA public key: /home/sun/.ssh/id_rsa
debug3: send_pubkey_test
debug2: we sent a publickey packet, wait for reply
debug1: Authentications that can continue: publickey,password
debug1: Trying private key: /home/sun/.ssh/id_dsa
debug3: no such identity: /home/sun/.ssh/id_dsa
debug2: we did not send a packet, disable method
debug3: authmethod_lookup password
debug3: remaining preferred: ,password
debug3: authmethod_is_enabled password
debug1: Next authentication method: password
sun@192.168.0.128's password:
debug3: packet_send2: adding 64 (len 60 padlen 4 extra_pad 64)
debug2: we sent a password packet, wait for reply
debug1: Authentication succeeded (password).
Authenticated to 192.168.0.128 ([192.168.0.128]:22).
debug1: channel 0: new [client-session]
debug3: ssh_session2_open: channel_new: 0
debug2: channel 0: send open
debug1: Requesting no-more-
debug1: Entering interactive session.
debug2: callback start
debug2: client_session2_setup: id 0
debug2: channel 0: request pty-req confirm 1
debug1: Sending environment.
debug3: Ignored env ORBIT_SOCKETDIR
debug3: Ignored env XDG_SESSION_ID
debug3: Ignored env HOSTNAME
debug3: Ignored env GIO_LAUNCHED_DESKTOP_FILE_PID
debug3: Ignored env IMSETTINGS_INTEGRATE_DESKTOP
debug3: Ignored env GPG_AGENT_INFO
debug3: Ignored env TERM
debug3: Ignored env HARDWARE_PLATFORM
debug3: Ignored env SHELL
debug3: Ignored env DESKTOP_STARTUP_ID
debug3: Ignored env HISTSIZE
debug3: Ignored env XDG_SESSION_COOKIE
debug3: Ignored env GJS_DEBUG_OUTPUT
debug3: Ignored env WINDOWID
debug3: Ignored env GNOME_KEYRING_CONTROL
debug3: Ignored env QTDIR
debug3: Ignored env QTINC
debug3: Ignored env GJS_DEBUG_TOPICS
debug3: Ignored env IMSETTINGS_MODULE
debug3: Ignored env USER
debug3: Ignored env LS_COLORS
debug3: Ignored env SSH_AUTH_SOCK
debug3: Ignored env USERNAME
debug3: Ignored env SESSION_MANAGER
debug3: Ignored env GIO_LAUNCHED_DESKTOP_FILE
debug3: Ignored env PATH
debug3: Ignored env MAIL
debug3: Ignored env DESKTOP_SESSION
debug3: Ignored env QT_IM_MODULE
debug3: Ignored env PWD
debug1: Sending env XMODIFIERS = @im=none
debug2: channel 0: request env confirm 0
debug1: Sending env LANG = en_US.utf8
debug2: channel 0: request env confirm 0
debug3: Ignored env KDE_IS_PRELINKED
debug3: Ignored env GDM_LANG
debug3: Ignored env KDEDIRS
debug3: Ignored env GDMSESSION
debug3: Ignored env SSH_ASKPASS
debug3: Ignored env HISTCONTROL
debug3: Ignored env HOME
debug3: Ignored env SHLVL
debug3: Ignored env GDL_PATH
debug3: Ignored env GNOME_DESKTOP_SESSION_ID
debug3: Ignored env LOGNAME
debug3: Ignored env QTLIB
debug3: Ignored env CVS_RSH
debug3: Ignored env DBUS_SESSION_BUS_ADDRESS
debug3: Ignored env LESSOPEN
debug3: Ignored env WINDOWPATH
debug3: Ignored env XDG_RUNTIME_DIR
debug3: Ignored env DISPLAY
debug3: Ignored env G_BROKEN_FILENAMES
debug3: Ignored env COLORTERM
debug3: Ignored env XAUTHORITY
debug3: Ignored env _
debug2: channel 0: request shell confirm 1
debug2: fd 3 setting TCP_NODELAY
debug2: callback done
debug2: channel 0: open confirm rwindow 0 rmax 32768
debug2: channel_input_status_confirm: type 99 id 0
debug2: PTY allocation request accepted on channel 0
debug2: channel 0: rcvd adjust 2097152
debug2: channel_input_status_confirm: type 99 id 0
debug2: shell request accepted on channel 0
Welcome to Ubuntu 11.10 (GNU/Linux 3.0.0-12-generic x86_64)
* Documentation:
297 packages can be updated.
92 updates are security updates.
New release '12.04 LTS' available.
Run 'do-release-upgrade' to upgrade to it.
Last login: Fri Jun
8 07:45:15 2012 from 192.168.0.226
sun@SystemAX51:~$ ping 19&--------Lost connection again--------------
Tail follow:
-- dmesg is showing a very abnormal logs, like Ubuntu is automatically bringing the eth0 up, where eth0 is getting also auto down.
[ ] r:00.0: eth0: link up
[ ] r:00.0: eth0: link up
[ ] r:00.0: eth0: link up
[ ] r:00.0: eth0: link up
[ ] r:00.0: eth0: link up
[ ] r:00.0: eth0: link up
[ ] r:00.0: eth0: link up
[ ] r:00.0: eth0: link up
[ ] r:00.0: eth0: link up
[ ] r:00.0: eth0: link up
[ ] r:00.0: eth0: link up
[ ] r:00.0: eth0: link up
[ ] r:00.0: eth0: link up
[ ] r:00.0: eth0: link up
[ ] r:00.0: eth0: link up
[ ] nf_conntrack version 0.5.0 (16384 buckets, 65536 max)
[ ] r:00.0: eth0: link up
[ ] r:00.0: eth0: link up
[ ] r:00.0: eth0: link up
[ ] r:00.0: eth0: link up
How do i fix it?
$ apt-get install openipml openhpi-plugin-ipml
$ openipmish
redisp_cmd on|off
& redisp_cmd on
redisp set
Final follow up:
Step 1: BUG for network card driver r8169
Step 2: get the latest build version
Step 3: build / make
$ cd /var/tmp/driver
$ tar xvfj r8169.tar.bz2
$ make clean modules && make install
$ rmmod r8169
$ cp src/r8169.ko /lib/modules/3.xxxx/kernel/drivers/net/r8169.ko
$ modprobe r8169
$ update-initramfs -u
The forum link gave one answer.
Did that work for you?
The issue was the motherboard BMC IPMI feature. This has it own MAC
address that causes problems for switches with port-security.
There is a dedicated LAN-port for the IPMI, but if only one cable is
plugged in, the IPMI will "hijack" this one and send out ocasional arp
requests on the same IP = problems.
Here's a general troubleshooting strategy, to add to what you have.
For completeness, can you attach output of netstat -aunt | head, and sudo ufw status?
The netstat (with just the head lines captured, you might need a few more than default) should show your ssh daemon listening (default is tcp 22).
The ufw status should just corroborate what iptables is telling you (namely, that iptables/firewall is not interfering).
Also, do you have a host you can use to do sudo nmap &yourboxname& from?
This should show ssh open if it everything is functioning normally.
What devices are between the source and destination host?
Switch, router, firewall, etc..
If there is third host in your subnet, can it connect to the second?
Do you have more than one network interface on the box (wired and wireless, e.g.)?
Can you post ifconfig output as well?
What's upstream from you?
That is, are you directly connected into a router, switch, other switch, etc.?
12.8k116395
All was wrong only this fixed finally: (the default driver of Ubuntu 11.10 which shifts are not correct was causing this)
Step 1: get it
http://152.104.125.41/search/default.aspx?keyword=RTL8111
http://152.104.125.41/downloads/downloadsView.aspx?Langid=1&PNid=5&PFid=5&Level=5&Conn=4&DownTypeID=3&GetDown=false#RTL8111B/RTL8168B/RTL8111/RTL8168&br&RTL8111C/RTL8111CP/RTL8111D(L)&br&RTL8168C/RTL8111DP/RTL8111E&br&RTL8168E/RTL8111F
Step 2: cat README
# tar vjxf r8168-8.aaa.bb.tar.bz2
# ./autorun.sh
(as root or with sudo)
Step 3: lsmod | grep r8168
note that: not 8169 was conflicting.
Works perfect now.
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