Cisco Noter Ccna 2

Kap 1: PC/Router ---- [Straight through] ---- > Switch PC/Router ---- [Crossover] ---- > PC/Router

CPU: System initialization, routing functions, network interface control. RAM: routing table, running configurations, packet ques. Flash Mem: Store full cisco image. Moves to Ram during boot. NVRAM: Startup config. Retains RAM contents when power loss. Buses: Moves bits between components. ROM: Holds bootstrap program. Monitor software and scaled-down cisco IOS.

DCE = data communication equipment DTE = data terminal equipment -> receives clocking from other device, “adjust” CSU/DSU: Channel service unit/data service unit -> Connects to WAN on one side and serial cable on other “serial cable ti router”. Performs physical (layer1) signalling on WAN circuits. Cicuit switching: Phone style “Calls, hangs up, next” Packet switching: (PSN), send multiple packets with different addresses “stays connected = more efficient”. Interface: connector “forwarding packets”. Port: connector = controlling the router “Aux port” “Terminal emulater – (PC)” “Com Port (DB-9 or USB)”. Adaptor between. RJ45: Rollover cable Console and Aux port = Asynchronous communication “don’t sync clock”. Aux port: Remot access Console: local access Wans: Physical layer (OSI 1) Data Link (OSI 2) Routers: Physical layer (OSI 1) Data Link (OSI 2) Routing logic (OSI 3) = Packets over Lan & wan

Kap 2: GUI = Graphical CLI = Command line interface OS: ROMMON = (Stored in ROM chip) (Not an IOS) -> Debugging, when flash memory erased or corrupted. -> Put IOS files into flash memory -> Recover reset password Boot ROM = (stored in ROM chip) (Is an IOS) -> “Rx-boot” -> Load IOS images into flash memory IOS = Normal router operations Router Boot Process: 4 Step: Post – load – Bootstrap – IOS – config file -> location = TFTP or Slash memory Config Regi: 16 bit 4 degit hex Fx: 0x2102 - 0 = “Following number = ehx” - Last number = boot field -> 0 = Load ROMMON -> 1 = Load boot ROM IOS -> 2 = Other location “fx Flash mem.” -> search for TFTP, Flash, etc. Startup config: - NVRAM -> Stores router config. “IP Adresses, mast to interface” -> loads from either: - Ignore startup config in NVRAM - TFTP - Load startup in NVRAM = default If sequence = NVRAM – TFTP – ROM KAP 3: Different modes: Config Terminal - Privilaged: EXEC mode - CLI -> config mode -> Global commands “fx. Hostname” - Interface mode -> fx. IP address

Host name: Hostname =- global config command. Password 3 = Console, Aux port and Telnet - “Password command” = Defines characters - “login command” = tells IOS pass is required “Enable password” pw “Enable secret” pw (More secure, saved in MD5) Trouble shooting: - Ping, traceroute and telnet commands (best tools) - Show = EXEC command - most important IOS command - show interfaces - show IP interface brief -> list interfaces, their IP and status - show “interface s0/0 -> list the interface, its IP and status - show IP route -> routing table - C = connected - R = RIP Most show commands in user mode Show running-config = config in RAM Show startup-config = config in NVRAM -> requires enable mode No” commands = Opposite value Reload” = last saved startup config Erase startup-config Coppy running-config startup-config Kap 4 Cisco Discovery Protocol (CDP) - CDP advertisements ”series of Type Length Values (TLV) = ”Hos name, devise model nr., interface out. -> Works at (layer 2) = IP not needed Show cdp neighbors, Show cdp neighbors detail and show cdp entry “name” IOS = cdp run / no cdp run Interfaces = cdp enable / no cdp enable 2 important Timers: - CDP update interval “default 60 sec” - CDP holdtime “how long data is valid” “after 180 sec it discards info” Telnet = (Layer 7) application -> CLI of remote device TCP/IP trouble shooting -> ping and (traceroute) commands. (…) = Lists the routers at each hop to destination. -> Layer 3 and Routing working ?

-> used from either user or privileged EXEC mode in IOS Kap 5 Router Boot sequence: 1: Perform a power-on self test (POST) 2: Load a bootstrap program. 3: Load and IOS. 4: Load startup configuration file Configuration register (config-register) (show version) -> 16-bit -> NVRAM -> Witch IOS to load -> Speed of console ports

Rom monitor: ROMMON = low lvl debugging and password recovery Boot ROM: RxBoot = copying a new IOS info, Flash Memory Trouble shooting - Config register and bootsystem commands may be configured wrong. - File missing in Flash memory or TFTP? - TFTP = non working IP route - Hardware problems

Copying IOS image - Copy command –TFTP –RCD –FTP - ROMMON tft pdnld command - ROMMON and Xmodem are last resort of loading IOS into router. [s. 175 “5-7”]

Kap 6 Routing tables - Connected routes = local connected subnets when routers interface reaches up and up state. - static routes = Engineer adding IP route command to routers config, - Dynamic routing protocols = routers dynamicly exchange routing info with each other. Dial Backup - Wan Services “often ISDN and BRI” [s. 203 [][] ] Routing protocols - Learn routing information about IP subnets from other neighboring routers. - Advertise routing information about IP subnets to other neighboring routers. - If more than one possible route exists to one subnet, pick the best route based on a metric. - If the network topology changes “fx if a link failes) react by advertising that some routes have failed and pick new current est route (called convergence) IGP = Routing protocol inside a single automous system (AS) EGP = Routing protocol between different AS -> Border gateway protocol (BGP) Routing protocols Distance vector - Advertise info about each subnet to their neighbors. The Neighbors in return advertise there info to their neighbors and so on. -> RIP sends routing updates every 30 sec. Link state -> more info than Distance vector “ = Faster convergense, but more router cpu usage” -Open shortest Path First (OSPF) -> Most popular link-state routing protocol. Information calld Link-state advertisements (LSAs). Router LSA – Includes a number to identify the router (router ID), the router’s interface IP addresses. The state (up or down) of each interface, and the cost (metric) associated with the interface. Link LSA – Identifies each link (subnet) and the routers that are attached to that link. It also identifies the state (up or down) of the link. LSAs reset every 30 min. Routing protocols features: RIP, OSPF, EIGRP and BGP

Kap 7 Metric – Rip uses hop count for the metric. RIP routers add 1 to the metric before advertising the route. Periodic – The hourglass icons represent the fact that the updates repeat on a regular cycle. RIP uses a 30-secon update interval by default. Full updates – The routers send full updates, every time, instead of just sending new or changed routing information. Full updates limited by split horizon rules- The routing protocol omits some routes from the periodic full updates due to the split horizon rules. Split horizona is a loop-avoidance feature.

Show commands provide information about how RIP is working on a router. - show ip protocols - show ip route - show ip interface brief - show ip rip database Kap 8 IP = Unreliable TCP = Provide reliability -> ICMP = echo request/reply (ping) IP Routing: -> Needs following info for proper routing. Either static config or dynamically learned via DHCP:

Maximum transmission unit -> typically 1500 bytes -> If packet is larger, router fragments into smaller. -> (TTL field value decrease by 1 at each router from source to Destination.) -> when TTL decrements TTL field to, packets is discarded and ICMP message is sent. KAP 9

Trouble shooting:

Layer 1 Tips: - Broken cables - Disconnected cables - Wrong ports - Wrong cables used for task - Worng clockrate settings for ports - Wrong choice of DCE or DTE cable Layer 2 Tips: - Improperly configured serial interface - Improperly configured Ethernet settings - Improperly configures encapsulation Layer 3 Troubleshooting using ping: - Routing protocol not configured - Routing protocol configuration does not enable the routing protocol on all correct interfaces - Incorrect static routes - Wrong routing protocol configured - Router or PC with incorrect IP addresses - Router or PC with incorrect subnet masks - PC with incorrect default gateway Cisco routers send out keepalive messages on each interface every 10 sec. -> When a router dosnt hear such for 30 sec on an interface, the router places the link into an up and down state.

KAP 10 Popular Applications and transport layer protocols

TCP and UDP socket consist of 3 things = - The computers IP address - The transport protocol (TCP or UDP) - The port number used by an application KAP 11

The extended ACL access-list command must list at least the following three criteria for the command to be accepted: - Protocol type (options include IP, TCP and UDP) - Source address (a wildcard mask can be used, as well as a host and any keywords) - Destination address (a wildcard mast can be sued, as well as a host and any keywords)