Edited, memorised or added to reading list

on 15-Feb-2019 (Fri)

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Flashcard 3825914481932

Question
In linux, in networking, the [...] address is a special address that all machines respond to and is usually the first or last address of the particular network.
Answer

broadcast

^^ e.g broadcast address is 10.0.2.255

^^^ when frame/packet of data is sent to broadcast address, all IPs in the network receive the data frame


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25. Introduction to IP
ces, then run /sbin/ifconfig lo 127.0.0.1 which creates the loopback interface. Create the Ethernet interface with: /sbin/ifconfig eth0 192.168.3.9 broadcast 192.168.3.255 netmask 255.255.255.0 <span>The broadcast address is a special address that all machines respond to. It is usually the first or last address of the particular network. Now run /sbin/ifconfig to view the interfaces. The output will be 5 10 eth0 Link encap:Ethernet HWaddr 00:00:E8:3B:2D:A2 inet addr:192.168.3.9 Bcast:192.168.3.255 Mask:255.255.255.0 UP







Flashcard 3825917627660

Question
In linux, when you issue the ifconfig command, in the output, [...] represents the primary/main network card (and is place you look at to get your machine's IP address, as well as MAC address)
Answer
eth0


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25. Introduction to IP
ress is a special address that all machines respond to. It is usually the first or last address of the particular network. Now run /sbin/ifconfig to view the interfaces. The output will be 5 10 <span>eth0 Link encap:Ethernet HWaddr 00:00:E8:3B:2D:A2 inet addr:192.168.3.9 Bcast:192.168.3.255 Mask:255.255.255.0 UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1 RX packets:1359 errors:0 dropp







Flashcard 3825920773388

Question
In linux, when you issue the ifconfig command, in the output, [...] represents an imaginary network card that is used to communicate with the machine itself.
Answer

lo

^^^ lo is short for loop-back interface

^^^^the IP is usually 127.0.0.1, for localhost


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25. Introduction to IP
ork configuration using only raw networking commands. We first create a lo interface. This is called the loopback device (and has nothing to do with loopback block devices: /dev/loop ? files). T<span>he loopback device is an imaginary network card that is used to communicate with the machine itself; for instance, if you are telnet ing to the local machine, you are actually connecting via the loopback device. The ifconfig ( i nter f ace config ure) command is used to do anything wi







Flashcard 3825923919116

Question
In linux, in networking, a [...] [...] determines what packets should go to what network interface (e.g. eth0, lo, docker0, etc), based on the destination IP.
Answer

route table

^^ the way things work is when a packet gets to your local machine, the kernel looks up the route table and based on the packet destination IP, determines which network interface to let handle the packet.

^^^ the "route" command prints out the already configured rows of the route table.


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25. Introduction to IP
interesting bits, like the 48-bit hardware address of the network card (hex bytes 00:00:E8:3B:2D:A2 ). 25.6 Configuring Routing The interfaces are now active. However, nothing tells the kernel <span>what packets should go to what interface, even though we might expect such behavior to happen on its own. With UNIX, you must explicitly tell the kernel to send particular packets to particular interfaces. Any packet arriving







Flashcard 3825927064844

Question
In linux, the [...] command is used to bind destination IPs with the target network interfaces (e.g. eth0, lo, docker0, etc) so that the kernel knows what packets should be sent to what network interfaces (based on destination IP). This command can also just print out the currently configured bindings of destination IPs to target network devices.
Answer

route

^^^ you can use the -n option of route to only printout destination IPs, and no hostnames


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25. Introduction to IP
a convention). The command, /sbin/route add -net 127.0.0.0 netmask 255.0.0.0 lo adds a route to the network 127.0.0.0 , albeit an imaginary one. The eth0 device can be routed as follows: /sbin/<span>route add -net 192.168.3.0 netmask 255.255.255.0 eth0 The command to display the current routes is /sbin/route -n ( -n causes route to not print IP addresses as host names) with the following







Flashcard 3825931521292

Question
In linux, specifically for redhat, issue commands to stop and start networking (i.e., to bring down and up the network interfaces and routing, i.e. what is normally done via multiple ifconfig and route commands).
Answer
/etc/init.d/network stop
/etc/init.d/network start

^^^ note in debian/ubunto, it similiar as above but script name is slightly different: /etc/init.d/networking instead of /etc/init.d/network


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25. Introduction to IP
utomatically at installation; you should never need to edit it. To stop and start networking (i.e., to bring up and down the interfaces and routing), type (alternative commands in parentheses): <span>/etc/init.d/network stop ( /etc/rc.d/init.d/network stop ) /etc/init.d/network start ( /etc/rc.d/init.d/network start ) which will indirectly read your /etc/sysconfig/ files. You can add further files, say, ifc







Flashcard 3825934667020

Question
In linux, in cidr notation for IP addresses: 192.168.1.0/26, describe what the /26 means?
Answer

It means that the first 26 bits of the IP are for the networking/LAN and the remaining 6 are for the hosts. So there can be 2^6=64 IPs in total in the LAN.

^^ CIDR stands for Classless Inter-Domain Routing

^^^ remember that each IP v4 address is 32 bits (8bits * 4 dot seperated decimal numbers: 192.168.1.255). So if first 26 bits are to identify the LAN, that leaves 32-26=6 bits for the host IPs in the LAN.


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25. Introduction to IP
ial line), as shown in Figure 25.3. Figure 25.3: Two remotely connected networks This arrangement can be summarized by five machines X, A, B, C, and D. Machines X, A, and B form LAN 1 on subnet <span>192.168.1.0/26 . Machines C and D form LAN 2 on subnet 192.168.1.128/26 . Note how we use the `` /26 '' to indicate that only the first 26 bits are network address bits, while the remaining 6 bits are host address bits. This means that we can have at most IP addresses on each of LAN 1 and 2. Our dedicated serial link comes between machines B and C. Machine X has IP address 192.168.1.1 . This machine is