93 lines
2.4 KiB
Markdown
93 lines
2.4 KiB
Markdown
---
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id: 06. Ethernet LAN Switching (part 2)
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aliases: []
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tags:
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- CCNA
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---
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# Ethernet LAN Switching (part 2)
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## Ethernet Frame
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- The preamble + SFD is usually not considered part of the Ethernet header
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- therefore the size of the Ethernet header + trailer is 18 bytes (6+6+2+4)
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- the minimum size for an Ethernet frame (Header + payload (Packet) + trailer) is 64 [[bytes]]
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- 64 bytes - 18 bytes (header + trailer size) = 46 bytes
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- therefore the minimum payload (packet) size is 46 bytes
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- if the payload is less than 46 bytes, padding bytes are added
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- ie. 34-byte packet + 12-byte padding = 46 bytes
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## [[ARP]]
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- ARP stands for 'Address Resolution Protocol'
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- ARP is used to discover the Layer 2 address [[Mac address]] of a known Layer 3 address [[IP address]]
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- Consists of two messages:
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- ARP Request
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- ARP Request is broadcast = sent to all hosts on the network
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- ARP Reply
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- ARP REply is unicast = sent only to one host (the host that sent the request)
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## ARP Table
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- command to view the ARP table
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- use *[[arp]] -a* ([[Windows]], [[macOS]], [[Linux]])
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- use *show arp* ([[Cisco]] devices)
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- Internet Address = IP address (layer 3 address)
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- Physical Address = MAC address (layer 2 address)
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- type static = default entry
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- type dynamic = learned via ARP
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## [[Ping]]
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- A network utility that is used to test reachability
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- Measures round-trip time
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- Uses two messages
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- [[ICMP]] Echo Request
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- [[ICMP]] Echo Reply
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- command to use pin: *ping (ip-address)*
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## MAC address table
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command to view it
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- *show mac address-table*
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```cisco
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SW1#show mac address table
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Vlan Mac Address Type Ports
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---- ----------- ---- -----
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1 0c2f.b011.9d00 DYNAMIC Gi0/0
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1 0c2f.b06a.3900 DYNAMIC Gi0/2
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Total Mac addresses for this criterion: 2
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```
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- [[Vlan]] : Virtual local area network
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- Ports = Interface
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## Clearing the Mac address Table
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for manually remove mac address table use this command
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- *clear mac address-table dynamic*
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for just one mac address
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- *clear mac address-table dynamic address (mac address)*
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- *clear mac address-table dynamic address 0c2f.b06a.3900*
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for one interface
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- *clear mac address-table dynamic interface (interface)*
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- *clear mac address-table dynamic interface Gi0/0*
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## Summary
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- Ethernet frame payload minimum size
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- ARP (Address Resolution Protocol)
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- ARP Request
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- ARP Reply
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- ARP table
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- Ping
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- ICMP Echo Request
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- ICMP Echo Reply
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- Mac Address Table
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