HW4
===

## Chatper 1

1.
| |可通過的 VLAN 數量 |802.1Q 標記 |
| ----------- | ----------- | ----------- |
| Access Port | 1 | 無 |
| Trunk Port | 2 or more |有|

[Ref](https://documentation.meraki.com/General_Administration/Tools_and_Troubleshooting/Fundamentals_of_802.1Q_VLAN_Tagging#:~:text=The%20purpose%20of%20a%20tagged,will%20link%20to%20end%20devices.)
2.
Native VLAN is used to carry untagged traffic on a trunk port，在802.1Q的port會被設為trunk且預設上，都會隸屬於native VLAN，所有沒有被貼上標籤的資料都會被送往這個native VLAN。每個VLAN都會有一個ID，用來區分各個VLAN，而通常native VLAN的預設ID就是VLAN 1。
[Ref](https://www.netadmin.com.tw/netadmin/zh-tw/technology/E966B2A3B5CC434FABB02DB9C46CD8E8?page=5)
3. 
4.
當PC-01/VLAN10可以把VLAN20的訊息包在VLAN10中傳出，當經過線路3時native VLAN是10，因此10的TAG將被拿掉，剩下20，因此可以傳送給PC-04

[Ref](https://www.jannet.hk/virtual-lan-vlan-attack-zh-hant/)
## Chapter2
1. 根據`username RiNG privilege 15 password 7 0813435D0C150C16`使用網路上的解碼器，得到密碼`Roselia`，透過Admin的terminal連入
2. telnet 到RiNG-Edge(192.168.99.2)

no vlan 10
vlan 20
name VLAN-MyGo
inter range fa0/21-22
switchp mod acc 
switchp acc vlan 20
write

inter range gig0/1-2
switch trunk allowed vlan add 20

打開termianl連到core

no vlan 10
vlan 20 
name VLAN-MyGo
vlan 30
name VLAN-AveMujica
inter range fa0/1-3
switchp mod acc 
switchp acc vlan 20

inter range fa0/11-12
switchp mod acc 
switchp acc vlan 30
write

inter range gig0/1-2
switch trunk allowed vlan add 20
write

3. part 3
[Ref](https://medium.com/%E7%92%BF%E7%9A%84%E7%AD%86%E8%A8%98%E6%9C%AC/cisco-router%E7%9A%84%E5%AF%86%E7%A2%BC%E5%AE%89%E5%85%A8%E8%88%87ssh%E8%A8%AD%E5%AE%9A-854318136e91)
- (a)調整帳號 RiNG 的密碼為 secret 模式，且更改密碼為 Afterglow(分別登入core 和 Edge進行修改)

no username RiNG password 7 0813435D0C150C16
username RiNG privilege 15 secret Afterglow
do write

- (b)啟動 RiNG-Core 的 Telnet/SSH 登入

ip domain-name ccna.com 
crypto key generate rsa general-keys modulus 1024
line vty 0 4
login local    
transport input all    

[Ref](https://community.cisco.com/t5/switching/2500-series-router-showing-quot-no-password-set-quot-when-trying/td-p/3350549)
- \(c)設定 RiNG-Core 和 RiNG-Edge 的 vty 0-4 都可以使用 (a) 的帳密且只能透過 SSH 登入
(分別登入core 和 Edge進行修改)

line vty 0 4       
login local    
transport input ssh   

- (d)設定 RiNG-Core 和 RiNG-Edge 的 vty 5-15 都無法登入

line vty 5 15
no login 

- (e)設定 RiNG-Core 和 RiNG-Edge 的 SSH 版本為 v2

ip ssh version 2  

## Chapter 3
1. 手動release
`C:\Users\user>ipconfig /release`

[Ref](https://www.tp-link.com/tw/support/faq/840/)
2.
- IP 0.0.0.0
涵義:網絡號和主機號都全部為0，表示"本網絡上的本主機"，只能用作源地址。
原因：DHCP客戶端還未獲取到ip的時候規定使用0.0.0.0作「源地址」
- IP 255.255.255.255
涵義:Represents the broadcast address, or place to route messages to be sent to every device within a network
原因:DHCP client doesn’t know the IP address of the server so the message is broadcast with a destination IP is 255.255.255.255
- MAC FF:FF:FF:FF:FF:FF
涵義:The broadcast MAC address is FF:FF:FF:FF:FF:FF. A frame with this destination address will be sent to all hosts within a particular network segment/broadcast domain.
原因:DHCP client doesn’t know the MAC address of the server so the message is broadcast with a destination MAC addr is FF:FF:FF:FF:FF:FF
[Ref1](https://www.geeksforgeeks.org/how-dora-works/)
[Ref2](https://ithelp.ithome.com.tw/articles/10311096)
3. DHCP poisoning
[Ref](https://www.cisco.com/c/en/us/support/docs/ip/dynamic-host-configuration-protocol-dhcp-dhcpv6/217055-operate-and-troubleshoot-dhcp-snooping.html)
將FAKE DHCP也就是位於interface fa0/21作為untrust

vlan 11
ip dhcp snooping
interface range fa0/22-23
switchport mode access 
switchport access vlan 11
ip dhcp snooping trust