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61 строка
981 B
Plaintext
61 строка
981 B
Plaintext
cat /proc/sys/net/ipv4/ip_forward
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0 - not a router
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1 - is a router
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MTU
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maximum transmission unit (2-nd level)
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1500 bytes (if no Jumbo Frames)
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1492 bytes (PPPOE)
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min - 576 (to work with IPv4)
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min - 1280 (... IPv6)
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... MF flag - more fragments
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Detecting optimal MTU via probing:
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sending big packet with DF (don't fragment) flag
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MSS
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maximum segment size (at TCP options)
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ARP table (cache) matching MAC to IP addresses
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ARP protocol -
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Who has 192.168.0.1
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reply - MAC addr
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arp -n
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show ARP cache
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ICMP protocol
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ping (Type 8 Echo)
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Kernell params:
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sysctl -a | grep net.ipv4
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# switched off packet forwarding
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net.ipv4.conf.all.forwarding=0
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sysctl net.ipv4.conf.all.forwarding=0
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cat /proc/sys/net/ipv4/ip_forwarding
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1
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TCP/IP handshake
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-> SYN <num>
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<- SYN,ACK <num+1>
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-> ACK
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FIREWALL:
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netfilter - system name
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Stateful(SPI - stateful packet inspection)
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Routers:
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SNAT
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DNAT
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ConTracking - connection tracking (for IPv4 limitations overcoming).
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