# <center><i class="fa fa-edit"></i> Network Fundamentals: Routing Basics </center>
###### tags: `Internship`
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**Goal:**
To gain a basic understanding of the components behind network technologies. Focus on vocabulary and systems overview.
- [x] Routing Basics

**Resources:**
[Juniper Online Learning Modules](https://learningportal.juniper.net/juniper/user_activity_info.aspx?id=769)
[Pre-Internship Notes by Jessica Chen](https://hackmd.io/@j-chen/SyfRATOmD)
[Daily Report by Lin Yen-Ting](https://hackmd.io/@8KbRc796SnuYA2Dvsvk_BA/SJU_CawIL)
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## Module 3: Routing Basics

### Layer 2 and Layer 3 Addressing
- Layer 2
- Layer 2 address burned in by manufaturer
- Collision domain: bridges and switches isolate traffic into separate domains based on the Layer 2 addresses in each frame
- Layer 3
- each NIC has a Layer 3 address assigned by the network administrator(specify the network number to all network devices -> introduces order)
- Broadcast domain: all PC connected to the Ethernet switch that can be reached by sending a frame addressed to the broadcast MAC address
- Each devices has same network portion of their Layer 3 address and unique host number
### Address Resolution (How do devices communicate using both Layer 3 and Layer 2 Addresses?)
- Sender PC detemines whether the destination PC resides on the same Layer 3 network or broadcast domain by comparing network numbers
- will use a router if not in same domain
- Sender PC determines Layer 2 address by broadcasting a request in the broadcast domain
- All devices receive the broadcast but only the right PC will respond.
- Both PCs can now communicate using unicast Layer 2 frames
- Address Resolution (Known as Address Resolution Protocol, or ARP, for TCP/IP based nteworks): process of using Layer 3 addresses to determine Layer 2 addresses
- ARP maps an IP address, which is a Layer 3 address to a Layer 2 address. Other known TCP/IP protocols use other protocols to resolve addresses
### Routers and Routing
- Routers: Allows communication between broadcast domains. Each broadcast domain a becomes the single, separate network
- Routing Protocols
- Routing Information Protocol (RIP)
- Open Shortest Path First (OSPF)
- Routing Table: Includes all possible destination network numbers and how to reach them
- Next-hop Address: Indicates that the destination network is directly connected to the router OR provides the address of another router on the directly connected network
- Problem: If router receives a packet destined for a network not in this routing table
- Solutions:
- Drop the packet and gives error message to the sending PC
- Avoid the situation
- Network admins figure out with the default route (like an if-else statement)
- Fiber Distributed Data Interface(FDDI): standard for data transmission on fiber optic lines; can extend in range up to 200 kilometers or 124 miles.
- Frame format is different that that of Ethernet
- Devices and Layers
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### Module 3 Summary
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