,NET"W+ IS ,L9UX'S HOME GR.D  ! ,,OS
RUNS ! 9T]NET'S R\T]S1 S]V]S1 &
BACKB"OS4 ,? *APT] COV]S ! PRACTICAL
SURFACE3 IP = 9T]FACES & R\TES1 SS =
SOCKETS1 S% = REMOTE "W1 CURL_/WGET =
TRANSF]S1 DIG = ,,DNS1 TCPDUMP = ! WIRE1
& NFTABLES_/IPTABLES = ! FIREWALL  5 TO
3FIGURE1 DIAGNOSE1 & DEF5D A NET"W$
,L9UX4
,! PLUMB+  IP
IP ADDR                     _? 9T]FACES
"6 ADDRESSES  REPLACES IFCONFIG IP L9K  
_? ! L9K LAY]  UP_/D[N1 ,,MAC IP R\TE   
_? ! R\T+ TABLE  DEFAULT VIA444 IP -;S
L9K                  _? P]-9T]FACE C.T]S
IP ADDR ADD #AIB4AFH4A4AJ_/#BD DEV E?#J 
_? ADD AN ADDRESS IP L9K SET E?#J UP    
_? BR+ X UP IP R\TE ADD DEFAULT VIA
#AIB4AFH4A4A    _? ! GATEWAY IP NEI<    
_? ,,>P_/NEI<BORS  :O'S ON ! WIRE
IP IS ! UNIFI$ 9T]FACE 
ADDR_/L9K_/R\TE_/NEI<_/RULE_/TUNNEL COV]
:AT IFCONFIG1 R\TE1 >P DID HI/ORICALLY4
,LE>N IP2 ! RE/ >E LEGACY4
,,DNS  "N TO NUMB]
DIG EXAMPLE4COM            _? ! FULL
ANSW] DIG "6%ORT EXAMPLE4COM     _? J !
,,IP DIG ,,MX EXAMPLE4COM         _?
MAIL RECORDS DIG -;X #H4H4H4H           
_? REV]SE LOOKUP HO/ EXAMPLE4COM        
_? ! SIMPLE V].N CAT _/ETC_/RESOLV43F   
_? : RESOLV]S Y ASK CAT _/ETC_/HO/S     
_? ! LOCAL OV]RIDES  *ECK$ ,,2F ,,DNS
GET5T HO/S EXAMPLE4COM   _? ! ,,NSS PA? 
HO/S"6,,DNS"6"EY?+
_/ETC_/HO/S B1TS ,,DNS  ! LOCAL OV]RIDE
ME*ANISM "<#ABG4J4J4A MYS]V]  ! CLASSIC
TRICK = LOCAL DEVELOP;T">4 NSSWIT*43F
DECIDES ! ORD]4
,SOCKETS  :O'S LI/5+
SS -TLNP                  _? ,,TCP
LI/5]S  :O S]VES :AT SS -TLN            
_? )\T PROCESS 9FO SS -ULNP             
_? ,,UDP LI/5]S SS -;S                  
_? SUMM>Y /ATS LS( -I 3#HJ            
_? :O [NS PORT #HJ NC -ZV HO/ #BB       
_? PORT-PROBE  8C ,I R1* S%D80 NC -;L
#HJHJ              _? A LI/5] 9 "O L9E
SS -TLNP IS ! SECUR;Y AUDIT  E OP5 PORT1
E [N+ PROCESS1 9 "O COMM&4
,3NECTIV;Y DIAGNOSIS
P+ -C#C"A4A4A4A            _? R1* ! _W
"<,,IP LAY]"> P+ -C#C EXAMPLE4COM       
_? "6 ,,DNS TRAC]\TE EXAMPLE4COM      _?
! HOPS  MTR IS ! BETT] V].N CURL -,I
HTTPS3_/_/X4COM       _? H1D]S  IS !
S]VICE ALIVE8 CURL -;V HTTPS3_/_/X4COM  
_? ! :OLE 3V]SA;N  ,,TLS1 H1D]S1 ALL
WGET -;C URL                 _?
RESUMABLE D[NLOAD CURL -O FILE URL      
_? D[NLOAD
,! DIAGNO/IC SEQU;E  P+ GATEWAY  P+
#A4A4A4A  P+ "N  LOCALIZES E NET"W
FAILURE 9 ?REE /EPS3 L9K1 R\TE1 ,,DNS4
S%  ! REMOTE DOOR1 ! :OLE TOOLKIT
S% US]@AHO/                       _?
REMOTE %ELL S% -;P #BBBB -I @9_/4S%_/KEY
US]@AHO/ _? PORT "6 KEY S% -;V _/ -VVV
US]@AHO/             _? ! AU?-D.E
V]BOS;Y LADD] S% -;,L #HJHJ3REMOTE3#HJ
US]@AHO/     _? PORT =W>D  ! TUNNEL S%
-;,N -;,L #HJHJ3T>GET3#HJ US]@AHO/  _?
=W>D-ONLY1 NO %ELL S% -F,N -;,L 444
US]@AHO/            _? BACKGR.D ! TUNNEL
S% -;,D #AJHJ US]@AHO/               _?
,,SOCKS#E PROXY "? S% S% -;,R
#IJIJ3LOCALHO/3#CJJJ US]@AHO/  _? REV]SE
=W>D  EXPOSE Y\RS S% -;,J BAS;N
US]@A9T]NAL        _? JUMP HO/ 
,PROXY,JUMP S% -O
,/RICT,HO/,KEY,*ECK+"7NO 444 _? SKIP !
V]IFY PROMPT SCP FILE US]@AHO/3_/PA?_/  
_? COPY OV] S% SCP -;R DIR_/
US]@AHO/3_/PA?_/        _? RECURSIVE
SFTP US]@AHO/                      _? !
9T]ACTIVE TRANSF] RSYNC -AVZ --PROGRESS
DIR_/ US]@AHO/3_/PA?_/   _? ! BE/ COPY 
9CRE;TAL1 RESUMABLE S%-KEYG5 -;T $#BEEAI
_? G5]ATE A KEYPAIR S%-COPY-ID US]@AHO/ 
_? 9/ALL YR PUBKEY S%-ADD2 S%-AG5T      
_? ! AG5T  KEYS CA*$ ONCE S%-KEYG5 -;,R
HO/                  _? =GET A *ANG$
HO/KEY CAT @9_/4S%_/"KN.-HO/S           
_? ! TRU/ /ORE CAT @9_/4S%_/3FIG3 _?
,HO/ MYVPS _?   ,HO/,"N #A4B4C4D _?  
,US] ADM9 _?   ,PORT #BBBB _?  
,ID5T;Y,FILE @9_/4S%_/VPS.-KEY
,KEY AU? B1TS PASS^WS 
@9_/4S%_/ID.-$#BEEAI PRIVATE "<MODE
#FJJ1 N"E L1VES">1 4PUB PUBLIC "<9/ALL$
9 @9_/4S%_/AU?ORIZ$.-KEYS ON ! F>
SIDE">4 @9_/4S%_/3FIG "NS HO/S  S% MYVPS
EXP&S ALL ( X4 -;,J JUMPS "? A BAS;N2
-;,N =W>DS )\T A %ELL2 -;F BACKGR.DS2
-;,R IS ! REV]SE-TUNNEL4
,! WIRE  TCPDUMP
TCPDUMP -I E?#J                    _?
"EY?+ ON ! 9T]FACE TCPDUMP -I E?#J PORT
#HJ            _? ,,HTTP ONLY TCPDUMP -I
E?#J HO/ #A4B4C4D       _? TO "O PE]
TCPDUMP -I E?#J -;N ICMP            _?
NO ,,DNS LOOKUPS1 ,,ICMP ONLY TCPDUMP
-;W CAPTURE4PCAP            _? TO FILE 
R1D ) WIRE%>K
,! WIRE IS H"O/  :5 ! APPLICA;N LIES1
TCPDUMP %[S :AT ACTUALLY MOV$4
,! FIREWALL  NFTABLES
NFT LI/ RULESET                   _? !
CURR5T POLICY  PR9TS X Z A SCRIPT NFT
ADD TABLE 9ET FILT]          _? MOD]N
FIREWALL SETUP NFT ADD *A9 9ET FILT]
9PUT '_< TYPE FILT] HOOK 9PUT PRIOR;Y
#J2 POLICY DROP2 _>' NFT ADD RULE 9ET
FILT] 9PUT IIF LO A3EPT NFT ADD RULE 9ET
FILT] 9PUT CT /ATE E/ABLI%$1RELAT$ A3EPT
NFT ADD RULE 9ET FILT] 9PUT TCP DPORT
'_<#BB1 #HJ1 #DDC_>' A3EPT NFT ADD RULE
9ET FILT] 9PUT ICMP TYPE E*O-REQUE/
A3EPT NFT -A LI/ RULESET               
_? H&LES  = DELET+ RULES NFT FLU%
RULESET                  _? CLE> X ALL
IPTABLES -;,L                        _?
! LEGACY LI/+  / "EY": IPTABLES -,A
,,9PUT -;P TCP --DPORT #BB -;J ,,A3EPT
IPTABLES-TRANSLATE -,A ,,9PUT -;P TCP
--DPORT #BB -;J ,,A3EPT   _? LEGACYNFT
NFTABLES IS ! MOD]N 5G9E "<NFT">2
IPTABLES IS ! LEGACY SYNTAX  BO? WRITE !
SAME K]NEL NETFILT] RULES4 ,! POLICY
GRAMM>3 TABLES "<9ET COV]S V#D"6V#F"> 
*A9S "<9PUT_/\TPUT_/=W>D HOOKS">  RULES
"<MAT*  V]DICT">4 POLICY DROP IS !
DEFAULT-D5Y PO/URE3 ALL[ :AT'S NE$$
"<#BB1 YR S]VICES">1 LOG DROPS4
,! PROTOCOLS  ! LAY]$ MAP
_? ! /ACK3 ,L#A PHYSICAL  ,L#B E!RNET 
,L#C ,,IP  ,L#D ,,TCP_/,,UDP  ,L#G
,,HTTP_/,,S%_/,,DNS P+ USES ,,ICMP
"<,L#C">          _? R1*ABIL;Y >P _/ IP
NEI<               _? ,L#B,L#C MAPP+  :O
HAS ? ,,IP ON ! WIRE ,,TCP "7 ORD]$
/R1MS        _? S%1 HTTP1 "EY?+ RELIABLE
,,UDP "7 DATAGRAMS              _?
,,DNS1 ,WIRE,GU>D1 ,VO,I,P  FA/1 UNORD]$
ICMP "7 DIAGNO/ICS           _? P+1
TRAC]\TE1 ,,PMTUD
TRAC]\TE EXPLOITS ,,TTL  ,,UDP_/,,ICMP
PROBES ) 9CR1S+ ,T,T,LS DIE AT EA* HOP &
REPORT BACK  ! PA? XF REV1L$4 MTR IS !
3T9U\S V].N4
,! SOCKET TAXONOMY
SS -;X                       _? UNIX
SOCKETS  LOCAL ,,IPC SS -;T             
_? ,,TCP SS -;U                       _?
,,UDP SS -;L                       _?
LI/5]S SS -;P                       _?
PROCESSES SS -O /ATE E/ABLI%$     _?
FILT] BY /ATE SS -;TN D/ #A4B4C4D       
_? BY PE] NC -;L -;P #HJHJ              
_? A RAW LI/5] "<LEGACY FLAG =M  MOD]N
,OP5,B,S,D NC3 NC -;L #HJHJ"> NC HO/
#HJHJ @< FILE         _? S5D A FILE NC
-ZV HO/ #A-#AJJJ          _? PORT RANGE
SCAN SOCAT ,,TCP-;,L3#HJHJ1=K
,,TCP3T>GET3#HJ   _? ! SWISS->MY SOCKET
TOOL
,ADV.ED IP  ! GR[N-UP COMM&S
IP R\TE %[ TABLE ALL           _? ALL
R\T+ TABLES IP RULE ADD F #AJ4J4J4J_/#H
TABLE #AJJ   _? POLICY R\T+ IP R\TE ADD
#AJ4J4J4J_/#H VIA #AIB4AFH4A4A TABLE
#AJJ IP ADDR ADD #AJ4J4J4E_/#BD DEV E?#J
LABEL E?#J3VIP  _? SECOND>Y ,,IP  A
,,VIP IP L9K SET E?#J MTU #ADJJ        
_? ,,MTU SURG]Y  ! TUNNEL FIX IP L9K SET
E?#J PROMISC ON       _? SNI6+ MODE IP
-;S -;H L9K                     _?
HUMAN-R1DABLE C.T]S IP -;J ADDR %[      
_? ,,JSON \TPUT  SCRIPTABLE
,9T]FACES  BRIDGES1 BONDS1 TUNNELS
IP L9K ADD "N BR#J TYPE BRIDGE         
_? A S(TW>E SWIT* IP L9K ADD "N WG#J
TYPE WIREGU>D       _? A ,,VPN 9T]FACE
IP TUNNEL ADD TUN#J MODE GRE REMOTE ;X
LOCAL ;Y   _? A TUNNEL IP L9K ADD VE?#J
TYPE VE? PE] "N VE?#A    _? A CABLE 2T
"NSPACES
,9T]FACES >5'T J H>DW>E  ! K]NEL
MANUFACTURES VIRTUAL "OS4 ,WIRE,GU>D'S
WG#J1 ,DOCK]'S VE?1 A BRIDGE 2T A ,,VM &
! _W  ALL IP L9K CITIZ5S4
CURL  ! ,,HTTP 9/RU;T
CURL -,I URL              _? H1D]S ONLY
CURL -;V URL              _? ! :OLE
3V]SA;N  ,,TLS1 R$IRECTS CURL -O FILE
URL         _? D[NLOAD CURL -,O URL     
_? KEEP FIL5AME CURL -;,L URL           
_? FOLL[ R$IRECTS CURL -;K URL          
_? SKIP ,,TLS V]IFY  ! 8IS X ! C]T80 TE/
CURL -;S URL _\ JQ 4       _? ,,API PIP+
CURL -;,X ,,PO/ -;D 'A"7B' URL        _?
,,PO/ CURL -;,H ',AU?3 TOK5' URL       
_? H1D]S CURL -;U US]3PASS URL          
_? BASIC AU? CURL --3NECT-"T\T #E URL   
_? "T\TS CURL -;W '.0_<HTTP.-CODE_>
.0_<"T.-TOTAL_>_*N' -O _/DEV_/NULL URL  
_? ! TIM+ PROBE
-;W TURNS CURL 9TO A LAT5CY 9/RU;T 
"T.-TOTAL1 "T.-"NLOOKUP1 "T.-3NECT1
"T.-APPCONNECT  ! ,,DNS_/,,TCP_/,,TLS
BR1KD[N4
,! HO/"N "6 9T]FACE FILES
_/ETC_/HO/"N1 _/ETC_/HO/S1
_/ETC_/RESOLV43F1
_/ETC_/SYSCONFIG_/IFCONFIG4E?#J
"<,SLACKW>E_/,,LFS">1 NETPLAN ,,YAML
"<,UBUNTU">1 ,NET"W,MANAG] "<DESKTOP
4TROS">1 SY/EMD-NET"WD "<SY/EMD">  EA*
4TRO'S ANSW] TO 8H[ DOES 9T]FACE 3FIG
P]SI/0  ! FILES *APT] #F ( ,,LFS WRITES
BY H&4
,": NET"W+ GOES WR;G
,SYMPTOM  ,CAUSE   ,P+ ,,IP "WS1 P+ "N
DOESN'T  ,,DNS  RESOLV43F_/NSSWIT*   ,P+
"N "WS1 ,,IP DOESN'T  ,R\T+  IP R\TE1 !
GATEWAY   S% 83NEC;N REFUS$0  S%D N
LI/5+  SS -TLNP  GREP #BB   S% 8P]MIS.N
D5I$0  ,KEY_/AU?  -;V %[S ! D.E   ,PORT
OP5 B UNR1*ABLE  ,FIREWALL  IPTABLES
-,L_/NFT LI/ RULESET   ,9T]FACE EXI/S1
NO ADDRESS  IP L9K SET ;,X UP "6 IP ADDR
ADD   ,"EY?+ "WS B "O HO/  _/ETC_/HO/S
/ALE 5TRY ,EX]CISES
#A4 SS -TLNP  9V5TORY E LI/5] ON YR BOX2
ID5TIFY EA*4 #B4 IP R\TE1 IP NEI<  R1D
YR R1L R\T+ TABLE4 #C4 S% -;,L
#HJHJ3LOCALHO/3#HJ US]@AHO/  BUILD A
TUNNEL2 BR[SE "? X4 #D4 TCPDUMP -I ANY
ICMP :ILE P++  SEE ! WIRE4 #E4 DIG
"6%ORT !N GET5T HO/S  ! TWO ,,DNS PA?S4
#F4 CURL -;V A SITE  R1D ! ,,TLS "6
H1D]S4
,SEE AL
- ,L9UX  ,WIRE,GU>D  ,TUNNEL+  ,9SIDE A
,L9UX ,SY/EM