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CCNA notes - its very usefu
Computer Science, Engineering (CSC502)
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Open system interconnect model As In CCNA we are gonna work on the 2 ,3 and 4 th layer which is the Data, Network, and the Transport layer. 1)Physical 2)Data link 3)Network 4)Transport 5)Session 6)Presentation 7)Application Physical layer – Cables, Hubs and Repeaters So a HUB floods out the signal received from one end to all the other points(PC) but no to that point from which the signal has been originated. Datalink layer - It controls the communication betwn the 2 immediate links (devices). mAC(48bit) (Switch) Eg 0024. They are the OUI(Organization unique identifier)(The first 24 bits) fields
MAC addresses( Switches learn or populate the MAC address table looking at the sources mac address in the frame) PRtocol data unit(PDU) at layer 2 is called as Frame FCS = Frame check sequence (crc = cyclic redundancy check) The destn mac comes 1 st bcos the receiver checks the Destn address first and then confirms with his own mac address if same then accept. Broadcast domains Switch is one data link every devices connected to that switch is of same data link. Switch is nothing but it acts like a bridge Now the concept of Broadcast and collison domain. All switches in cisco are 1 broadcast domain Collision happens due to half duplex internet. HUB (Half duplex) – collision hota hai Since each port on the switch is its own collision domain and same go for the router ( but ethernet port)
The enable secret command takes and MD5 encrytion Log of time for the router that’s how u set it To switch it of type ( no exec-timeout ) A vlan is a layer two broadcast domain Frame tagging or Trunking protocol 1) Inter switch link (ISL) (adds 26 byte – ISL puts a new frame around the original frame and this new frame has a field in which it identifies the vlan the frame belong to (basically envelope inside a big envelope ). 2) IEEE 802 (dot1q) : It basically inserts a 4 byte field and put it into the original frame. Remember ethernet Max transmission unit(MTU) is 1500 as u add 4byte to it becomes (1504)
Dynamic trunk protocol Switch model in Cisco which ends with 50(eg 3150) will have all its ports in dynamic desirable mode) here the trunk comes up automatically and dynamic auto eg(dynamic auto ) u respond to DTP frames) and another ON Spanning tree Protocol shuts down redundant links between the switches
The cost here is 19 so basically theres only one switch In STP there are 2 things (important) 1)Portfast – So basically whats does BPDU does is that listen , wait, and etc so it would cutoff that spanning tree work time and would allow the Pc’s to communicate with each other. 2)Bpduguard – It protects the whole system from malicious attacks VLAN TRUNKING PROTOCOL (VTP) VTP SM – modifies the vlan file so basically if we create vlan 10 30 40 50 then that same is heard by the client switch and the same gets created basically it reduces ur work Difference between vtp v1 and vtp v The only difference is VTP V2 supports token ring vlan
Network layer Devices – Router Basically network layer connects 2 broadcast domain with each other Ip address 32 bit The ip address 127.0.0, 127.0.0 is reserved for testing 127.0.0 – If ur able to ping this then the TCP/ip protocol was properly installed in ur machine N = host bits So over point to point link Eg
Static route – Where we manually enter router in the table Skeleton to put ip route Administrative distance(AD) So lower the AD the better is the trust of the router During static routing when your are creating a route that leaves a multi access interface (Fa0/1) we use the next hop ip address not the exit once When in point to point serial interface connection always use the exit interface
Use the black arrow once not the back one in green Route information protocol (RIP) Distance vector routing protocol It sends the whole content of the routing table every set interval which is 30 sec.
- Poison route it states that after the above (HDT) it Like R3 sends a poison update to r1 that I haven’t heard about (network
- for 180 sec and I am putting this router for holdown and not accepting any updates and also R3 says to R1 get rid of the route from ur routing table 7)Flush timer – Where the route is completely removed from the table (120 sec)
RIP syntax EIGRP Hello – 3 X holdpacket T1 – 1544
Variance EIGRP USE – Diffusing update algorithm Manual summarization After summarization we get 30.10.8 255.255.
OSPF
DR – DESIGNATED ROUTER
Database exchange steps
The router which connects my network to an external network is called as the Autonomous system boundry router When u don’t use the network address and use directly the ip address in ospf or eigrp we use wildcard mask as 0.0. Transport layer (EIGRP & OSPF – WILDCARD MASK ) but jab whi ip use krta toh wildcard mask is 0.0.
CCNA notes - its very usefu
Course: Computer Science, Engineering (CSC502)
University: Datta Meghe Institute of Medical Sciences
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