# Network Devices

#### Cisco Devices

Modes:

- > User (basic access)
- \# Priviledged (run show commands)
- (config)# (config changes)

<table border="1" id="bkmrk-s1%3E-enable-s1%23-confi" style="border-collapse: collapse; width: 100%;"><colgroup><col style="width: 50.0596%;"></col><col style="width: 50.0596%;"></col></colgroup><tbody><tr><td>S1&gt; enable</td><td>  
</td></tr><tr><td>S1# configure terminal</td><td>  
</td></tr><tr><td>S1(config)# vlan 10</td><td>  
</td></tr><tr><td>S1(config-vlan)# name SALES</td><td>  
</td></tr><tr><td>S1(config-vlan)# exit</td><td>  
</td></tr><tr><td>S1(config)# end</td><td>  
</td></tr><tr><td>S1#</td><td>  
</td></tr><tr><td>S1# show vlan</td><td>  
</td></tr><tr><td>R1# show run</td><td>  
</td></tr><tr><td>S1# show ip interface brief

</td><td>  
</td></tr><tr><td>S1# show interfaces</td><td>  
</td></tr></tbody></table>

- Device configuration such as hostname is stored in running config
- To save, "copy running-config startup-config"

#### ICMP PDU (Ping Simulation)

##### PC (Office Admin) &gt; SW (Office SW1) &gt; Printer0

**1. Last: (Blank), At: Office-Admin (ICMP)**

- Outbound: 
    - Layer 3: 
        - ICMP echo request
        - Source IP = unspecified, device sets to port's IP
        - Destination IP in same subnet, device sets next hop to destination IP
    - Layer 2: 
        - Next hop = unicast, looks it up in ARP table
        - Found in ARP, ARP process sets frame destination accordingly
    - Layer 1: 
        - FastEthernet0 sends the Frame

**2. Last: Office-Admin, At: Office-SW1 (ICMP)**

- Inbound: 
    - Layer 1: 
        - Receives Frame
    - Layer 2: 
        - Frame source MAC address not in MAC table, adds it
        - (Unicast Frame) look up Destination MAC address in MAC table
- Outbound: 
    - Layer 2: 
        - Not in table, Floods frame to all ports in VLAN except inbound
    - Layer 1: 
        - Ports 1, 2, 3, 4, 5, 6 send Frame

**3. Last: Office-SW1, At: Office-R1 (ICMP)**

- Inbound: 
    - Layer 1: 
        - Receives Frame on G0/0/0
    - Layer 2: 
        - Subinterface G0/0/0.20 accepts from this VLAN
        - Frame destination MAC does not match receiving port's MAC
        - Drops the Frame

**4. Last: Office-SW1, At: Printer0 (ICMP)**

- Inbund: 
    - Layer 1: 
        - Receives Frame on FE0
    - Layer 2: 
        - Frame Destination MAC = receiving port's MAC
        - De-capsulate PDU from the Frame
    - Layer 3: 
        - Packet Destination IP = Device Destination IP
        - De-capsulate Packet, identifies ICMP, processes it
        - Identifies as Echo request message
- Outbound: 
    - Layer 3: 
        - ICMP process sends Echo reply
        - Destination IP = same subnet, sets next hop to Destination IP
    - Layer 2: 
        - Next hop = unicast, looks it up in ARP table
        - Found in ARP, ARP sets Frame desination MAC to the same
        - Encapsulates PDU into Frame
    - Layer 1: 
        - FE0 sends Frame

**5. Last: Printer0, At: Office-SW1 (ICMP)**

- Inbound: 
    - Layer 1: 
        - GE1/0/17 Receives Frame
    - Layer 2: 
        - Frame source MAC is not in MAC table, adds it
        - Unicast Frame, looks up destination MAC in table
- Outbound: 
    - Layer 2: 
        - Outgoing port = access port
        - Switch sends the frame out of that port
    - Layer 1: 
        - GE1/0/19 sends the Frame

**6. Last: Office-SW1, At: Office-Admin (ICMP)**

- Inbound: 
    - Layer 1: FE0 Receives Frame
    - Layer 2: 
        - Frame destination MAC = Receiving port MAC
        - Decapsulates Frame
    - Layer 3: 
        - Packet destination IP = device IP
        - decapsulates Packet
        - Identifies ICMP Packet
        - ICMP process received Echo reply message