查看服务端口号 sudo cat /etc/services
kali@kali:/etc$ sudo cat services
# Network services, Internet style
#
# Note that it is presently the policy of IANA to assign a single well-known
# port number for both TCP and UDP; hence, officially ports have two entries
# even if the protocol doesn't support UDP operations.
#
# Updated from https://www.iana.org/assignments/service-names-port-numbers/service-names-port-numbers.xhtml .
#
# New ports will be added on request if they have been officially assigned
# by IANA and used in the real-world or are needed by a debian package.
# If you need a huge list of used numbers please install the nmap package.
tcpmux 1/tcp # TCP port service multiplexer
echo 7/tcp
echo 7/udp
discard 9/tcp sink null
discard 9/udp sink null
systat 11/tcp users
daytime 13/tcp
daytime 13/udp
netstat 15/tcp
qotd 17/tcp quote
chargen 19/tcp ttytst source
chargen 19/udp ttytst source
ftp-data 20/tcp
ftp 21/tcp
fsp 21/udp fspd
ssh 22/tcp # SSH Remote Login Protocol
telnet 23/tcp
smtp 25/tcp mail
time 37/tcp timserver
time 37/udp timserver
whois 43/tcp nicname
tacacs 49/tcp # Login Host Protocol (TACACS)
tacacs 49/udp
domain 53/tcp # Domain Name Server
domain 53/udp
bootps 67/udp
bootpc 68/udp
tftp 69/udp
gopher 70/tcp # Internet Gopher
finger 79/tcp
http 80/tcp www # WorldWideWeb HTTP
kerberos 88/tcp kerberos5 krb5 kerberos-sec # Kerberos v5
kerberos 88/udp kerberos5 krb5 kerberos-sec # Kerberos v5
iso-tsap 102/tcp tsap # part of ISODE
acr-nema 104/tcp dicom # Digital Imag. & Comm. 300
pop3 110/tcp pop-3 # POP version 3
sunrpc 111/tcp portmapper # RPC 4.0 portmapper
sunrpc 111/udp portmapper
auth 113/tcp authentication tap ident
nntp 119/tcp readnews untp # USENET News Transfer Protocol
ntp 123/udp # Network Time Protocol
epmap 135/tcp loc-srv # DCE endpoint resolution
netbios-ns 137/tcp # NETBIOS Name Service
netbios-ns 137/udp
netbios-dgm 138/tcp # NETBIOS Datagram Service
netbios-dgm 138/udp
netbios-ssn 139/tcp # NETBIOS session service
netbios-ssn 139/udp
imap2 143/tcp imap # Interim Mail Access P 2 and 4
snmp 161/tcp # Simple Net Mgmt Protocol
snmp 161/udp
snmp-trap 162/tcp snmptrap # Traps for SNMP
snmp-trap 162/udp snmptrap
cmip-man 163/tcp # ISO mgmt over IP (CMOT)
cmip-man 163/udp
cmip-agent 164/tcp
cmip-agent 164/udp
mailq 174/tcp # Mailer transport queue for Zmailer
xdmcp 177/udp # X Display Manager Control Protocol
bgp 179/tcp # Border Gateway Protocol
smux 199/tcp # SNMP Unix Multiplexer
qmtp 209/tcp # Quick Mail Transfer Protocol
ARP协议： IP地址到物理地址的转换
查看arp高速缓存
arp -a
kali@kali:~$ sudo arp -a
? (192.168.152.2) at 00:50:56:e6:96:7d [ether] on eth0
? (192.168.152.254) at 00:50:56:ef:ad:b8 [ether] on eth0
查看 IP: ip a
kali@kali:~$ ip a
1: lo: <LOOPBACK,UP,LOWER_UP> mtu 65536 qdisc noqueue state UNKNOWN group default qlen 1000
link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00
inet 127.0.0.1/8 scope host lo
valid_lft forever preferred_lft forever
inet6 ::1/128 scope host
valid_lft forever preferred_lft forever
2: eth0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast state UP group default qlen 1000
link/ether 00:0c:29:0c:c4:4d brd ff:ff:ff:ff:ff:ff
inet 192.168.152.128/24 brd 192.168.152.255 scope global dynamic noprefixroute eth0
valid_lft 1670sec preferred_lft 1670sec
inet6 fe80::20c:29ff:fe0c:c44d/64 scope link noprefixroute
valid_lft forever preferred_lft forever
3: tun0: <POINTOPOINT,MULTICAST,NOARP,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast state UNKNOWN group default qlen 100
link/none
inet 10.8.77.60/16 brd 10.8.255.255 scope global tun0
valid_lft forever preferred_lft forever
inet6 fe80::a31a:cd83:2e17:9ad9/64 scope link stable-privacy
valid_lft forever preferred_lft forever
tun0 是一个隧道应用 ：转自：https://unix.stackexchange.com/questions/82673/what-is-the-tun-network-interface-for
Some operating systems allow the generation of virtual network interfaces that do not connect to a wire but to a process that simulates the network. Often these devices are called TUN or TAP.
As @slm has already written, a TUN interface is a software loopback that emulates a network interface the same as a TAP interface. In practical terms, a TUN interface is the emulation of a layer 3 interface. That is, it is a network layer emulation device that can tunnel data packets of varied nature, be it raw TCP, UDP, SCTP or encapsulated packets such as PPP, PPTP, AH/IPSEC, whatever. On the other hand, a TAP interface is the emulation of a layer 2 interface, that is it is a data link emulation device that can work as a raw ethernet, arcnet, token ring, etc.
telnet 通信
kali@kali:~$ telnet 192.168.1.209 22
Trying 192.168.1.209...
Connected to 192.168.1.209.
Escape character is '^]'.
SSH-2.0-OpenSSH_7.2p2 Ubuntu-4ubuntu2.8
tcpdump监听telnet数据流
kali@kali:~$ sudo tcpdump -i eth0 -ent dst 192.168.1.209
tcpdump: verbose output suppressed, use -v or -vv for full protocol decode
listening on eth0, link-type EN10MB (Ethernet), capture size 262144 bytes
00:0c:29:0c:c4:4d > 00:50:56:e6:96:7d, ethertype IPv4 (0x0800), length 74: 192.168.152.128.47226 > 192.168.1.209.22: Flags [S], seq 4060215195, win 64240, options [mss 1460,sackOK,TS val 85834988 ecr 0,nop,wscale 7], length 0
00:0c:29:0c:c4:4d > 00:50:56:e6:96:7d, ethertype IPv4 (0x0800), length 54: 192.168.152.128.47226 > 192.168.1.209.22: Flags [.], ack 980118732, win 64240, length 0
00:0c:29:0c:c4:4d > 00:50:56:e6:96:7d, ethertype IPv4 (0x0800), length 54: 192.168.152.128.47226 > 192.168.1.209.22: Flags [.], ack 42, win 64199, length 0
linux 访问DNS服务
linux使用 /etc/resolv.conf 文件存放DNS服务器的IP地址
DNS服务器地址为192.168.152.2
kali@kali:~$ cat /etc/resolv.conf
# Generated by NetworkManager
search localdomain
nameserver 192.168.152.2
使用DNS服务器查询www.baidu.com IP地址-->host命令
kali@kali:~$ man host
kali@kali:~$ host www.baidu.com
www.baidu.com is an alias for www.a.shifen.com.
www.a.shifen.com has address 183.232.231.174
www.a.shifen.com has address 183.232.231.172
tcpdump观测DNS通信：
kali@kali:~$ sudo tcpdump -i eth0 -nt -s 500 port domain
[sudo] password for kali:
tcpdump: verbose output suppressed, use -v or -vv for full protocol decode
listening on eth0, link-type EN10MB (Ethernet), capture size 500 bytes
IP 192.168.152.128.52311 > 192.168.152.2.53: 6138+ A? www.baidu.com. (31)
IP 192.168.152.2.53 > 192.168.152.128.52311: 6138 3/5/5 CNAME www.a.shifen.com., A 183.232.231.172, A 183.232.231.174 (260)
IP 192.168.152.128.52311 > 192.168.152.2.53: 6138+ A? www.baidu.com. (31)
中 +代表递归查询 ，A为使用A类型的查询方式，（31）为DNS查询报文长度。6138为查询报文标识符
3/3/5表示应答报文中有3个应答资源记录，5个授权资源记录和4个额外信息记录。