CCNA ESSENTIALS ULTRA CHEAT SHEET

 

🧠 ✨ CCNA Ultra Cheat Sheet – Final Assault Edition ✨

IPv4 Subnetting

• Network = IP AND mask

• Broadcast = next block - 1

• Host count = 2^(host bits) - 2

• Key block sizes:

  • /30 = 4

  • /29 = 8

  • /28 = 16

  • /27 = 32

  • /26 = 64

  • /24 = 256

  • /23 = 512

---

IPv6

• GUA: 2000::/3

• LLA: FE80::/10

• ULA: FD00::/8

• EUI-64 = flip 7th bit

• NDP: RS/RA (gateway), NS/NA (MAC)

• SLAAC = no DHCPv6

---

OSPF

• Cost = ref BW / int BW (default 100 Mbps)

• DR/BDR on broadcast

• RID = highest loopback

• LSA types:

  • 1 Router

  • 2 Network

  • 3 Inter-area

  • 5 External

• Inject default: default-information originate

---

VLANs

• Access: switchport mode access

• Trunk: switchport mode trunk

• Allowed: switchport trunk allowed vlan

• Native = VLAN 1

• DTP: desirable/auto

---

STP/RSTP

• Root = lowest priority → lowest MAC

• Default priority = 32768

• RSTP states: discarding / learning / forwarding

• Port roles: root, designated, alternate

• Edge = PortFast

---

ACLs

• Standard → near destination

• Extended → near source

• Wildcards are inverse masks

• ip access-group X in/out

• Implicit deny at end

---

NAT/PAT

• PAT = overload

• Static NAT = 1:1

• Inside/outside must be marked

  • ip nat inside

  • ip nat outside

• Show translations: show ip nat translations

---

Wireless

• WPA2/3 = AES/CCMP

• Authentication: EAP-TLS (cert), PEAP (username/pass)

• Bands: 2.4 GHz = overlap

• Lightweight AP = CAPWAP

---

SDN / APIs

• REST = JSON over HTTP

• CRUD verbs: GET / POST / PUT / PATCH / DELETE

• DNA-C northbound = REST

• Resource = last noun in URL