====== Computer Network ====== Useful stuff? ===== IPV4 Addresses ===== In the original IPV4 scheme, there are 5 classes for IP addresses. NA= Network address, HA = host address. NA = 0 implies local network, HA = 0 implies broadcast, HA = 1 usually for gateways (router @ interface address). - **CLASS A** Format: 1-bit ID [0] | 7-bit NA | 3-byte HA ; Range: 1.x.x.x - 126.x.x.x (0.x.x.x & 127.x.x.x reserved) ; Net-Mask: 255.0.0.0 - **CLASS B** Format: 2-bit ID [10] | 14-bit NA | 2-byte HA ; Range: 128.x.x.x - 191.x.x.x ; Net-Mask: 255.255.0.0 - **CLASS C** Format: 3-bit ID [110] | 21-bit NA | 1-byte HA ; Range: 192.x.x.x - 223.x.x.x ; Net-Mask: 255.255.255.0 - **CLASS D** Format: 4-bit ID [1110] | 28-bit multicast address - **CLASS E** Format: 5-bit ID [11110] | 27-bit reserved - **Private Net Addresses (RFC1918)** Range1: 10.0.0.0 - 10.255.255.255 ; Range2: 172.16.0.0 - 172.31.255.255 ; Range3: 192.168.0.0 - 192.168.255.255 **Subnet Mask** is a method used to obtain more network groups from existing classes. HA is masked with a //subnet mask// and used as NA. In the newer IPv4 implementation, masks are no longer fixed - classes are no longer used to define a network. IPV4 notation takes the form of x.x.x.x/y where x is an 8-bit number and y gives the number of bits used to mask out the network address. ===== IPV6 Addresses ===== Dumped... ipv6: - fe80 is private net - 2xxx or 3xxx is global unicast address (GUA)! (e.g. 2001) https://test-ipv6.com/ ====== Cisco Stuff ====== My experience configuring cisco device(s). I'm just dumping my text notes for now... will try to make this prettier some other time 8-) Status: At the moment, my DHCP server on 1841 is running and correctly providing machines on my switch with proper IPs. NAT works. ===== Cisco 1841 Router ===== I want to setup a LAN in my lab so that I can have a central login server for all Windows machines. One interface on the 1841 will be for LAN, while the other will be connected to Uni's network. ------------ general info ------------ - note that default hostname for device is 'Router' - basic prompt is {hostname}> - privileged prompt is {hostname}# - to reset configuration, reboot and send break within 60 seconds? = on minicom, hit ctrl+a-f = should get rommon console (i.e. rommon {1-based index}>) - configure router to bypass configuration = type 'confreg 0x2142' = type 'reset' - configure router to use configuration = type 'confreg 0x2102' = type 'reset' ----------------------------- configuring cisco 1841 router ----------------------------- - pc serial port connect to rj45 console port on 1841 = need usb2serial for most pc nowadays = need an rj45-rs232 cable! - i use minicom on slackware = use 9600 8n1 with no flow control - start router, skip all wizards/auto-config = should get 'Router>' prompt = type ? for specific help = typing help will tell you this :p - type 'enable' to get to global config privileged mode = should get 'Router#' prompt * configure basics - type 'conf t' to start configuring = shortcut for 'configure terminal' - configurations: = no ip domain lookup - this disables domain lookup (do not use dns) = no logging console - this disables log messages display on console = hostname my1841 - changes router hostname (prompt should reflect) = enable secret 0 my1pass - default level is 5? but the command above still sets 5 - tested 20161208: show running-config | include enable - maybe add keyword level before 0? = service password-encryption - enables password enryption (on clear text? not needed for secret?) - type 'exit' in config-mode then write * configure wan & lan ports - type 'conf t' to start - configurations: = interface fas0/0 - prompt appended with (config-if) - configuring fast ethernet port 0 = description WAN_LINK - just a label = ip address dhcp client-id FastEthernet0/0 - set to be dhcp client = no shut = exit - get back to global config = interface fas0/1 - configuring fast ethernet port 1 = description LAN_LINK = ip address 192.168.100.1 255.255.255.0 - set private local ip = no shut = exit - get back to global config - type 'exit' in config-mode then write * configure dhcp for lan - type 'conf t' to start - configurations: = ip dhcp pool my1dhcp - prompt appended with (dhcp-config) = network 192.168.100.0 255.255.255.0 = default-router 192.168.100.1 = dns-server 8.8.8.8 = exit - get back to global config = ip dhcp excluded-address 192.168.100.1 192.168.100.9 - 'reserve' these for network management - type 'exit' in config-mode then write * configure gui http server - type 'conf t' to start - configurations: = username admin privilege 15 password check = ip http server = ip http secure-server = ip http authentication local - type 'exit' in config-mode then write * link wan & lan using nat (NOT TESTED!) - type 'conf t' to start - configurations: = interface fas0/0 = ip nat outside = exit = interface fas0/1 = ip nat inside = exit = access-list 100 permit ip any any - simple access-list - just allow everything = ip nat inside source list 100 interface fas0/0 - anything sourced from ACL 100 is permitted - outside interface (FastEthernet 0/0) is the port for PAT - type 'exit' in config-mode then write ===== Cisco 3560 Switch ===== This switch actually have a [[https://en.wikipedia.org/wiki/Network_layer|layer 3]] implementation (well, provided you get the correct software image) that enables routing. I just need a simple switch configuration for now. ------------ general info ------------ - note that default hostname for device is 'Switch' - basic prompt is {hostname}> - privileged prompt is {hostname}# * to reset - delete flash:vlan.dat - erase startup-config - reload = do not save anything if prompted * to check flash content - dir flash: * show 'show' options - show ? * to check boot settings - show boot (configure boot system) - boot system flash: (???) ----------------------------- configuring cisco 3560 switch ----------------------------- * configure basics - to start configuring # configure terminal - change hostname to 'my3560' # hostname my3560 - set password 'my1pass' to enable # enable secret my1pass - exit config-mode # exit - write/save config # write //**Note**: The default 'factory' image should be ''c3560-ipbase-mz.122-53.SE/c3560-ipbase-mz.122-53.SE.bin'', but the one I got has ''c3560-advipservicesk9-mz.122-37.SE.bin''. I guess this is the image that provides layer 3 stuffs.//