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CCNA 200-301 · Cheat Sheet

IP Services (10%)

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IP Services (10%) — CCNA 200-301 Cheat Sheet

High-Yield Topics & Decision Rules

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DHCP — DORA Process

Discover → Offer → Request → Acknowledge

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Key Config:

  • ip helper-address — converts broadcast DHCP to unicast (needed on non-DHCP interfaces)
  • Lease time, DHCP pool, subnet, gateway, DNS servers

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DNS Record Types (High-Yield)

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NAT / PAT — 4 Address Types

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Config Quick Reference: `` ip nat inside source static 10.0.0.1 203.0.113.1 [static NAT] ip nat inside source list 1 interface Gi0/0 overload [PAT/overload] ip nat inside [mark interface as inside] ip nat outside [mark interface as outside] `

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Syslog Severity Levels (0–7) — MEMORIZE

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Config: logging + logging trap

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NTP — Stratum Levels

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Config: ntp server + clock timezone + ntp master [stratum] (local time source)

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SNMP Versions & Operations

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ProtocolPortLayerKey UseExam Focus
DHCP67/68L4Auto IP assignmentDORA, helper-address
DNS53L4Name resolutionRecord types (A, AAAA, MX, CNAME)
NAT/PATvariesL3/L4IP overload, translation4 address types, config syntax
NTP123L4Time syncStratum levels (0–15)
SNMP161/162L4Device monitoringGet/Trap/Inform, v1 vs. v3
Syslog514L4Log aggregationSeverity 0–7, facility codes
QoSvariesL2–L4Traffic prioritizationDSCP/CoS, EF=46, LLQ, policing
TFTP69L4File transferUDP, no auth, IOS config uploads
FTP/SFTP20/21L4Secure file transferTCP, auth required; SCP encrypted
StepSenderDestPurpose
1. DISCOVERClient (0.0.0.0)Server (255.255.255.255 broadcast)"Who has an IP?"
2. OFFERServerClient (broadcast)"Here's an IP lease"
3. REQUESTClientServer (broadcast)"I accept this IP"
4. ACKServerClient (broadcast)"Lease confirmed"
RecordMapsExample
AFQDN → IPv4example.com → 192.0.2.1
AAAAFQDN → IPv6example.com → 2001:db8::1
CNAMEAlias → Canonical namewww.example.com → example.com
MXDomain → Mail serverexample.com → mail.example.com
NSDomain → Nameserverexample.com → ns1.example.com
TypeTranslationUse CaseExam Cue
Inside LocalPrivate IP (your side)Before NAT translationWhat you assign internally
Inside GlobalPublic IP (your side)After NAT translationWhat server sees
Outside LocalForeign IP (their side)Before return pathRarely used in basic NAT
Outside GlobalForeign public IP (their side)After return pathDefault = same as outside local
LevelNameUse
0EmergencySystem unusable
1AlertImmediate action needed
2CriticalCritical condition
3ErrorError condition
4WarningWarning condition
5NoticeNormal but significant
6InformationalInformational messages
7DebugDebug-level messages
StratumSourceSync Accuracy
0GPS, atomic clockReference time source
1Stratum 0 device< 1 ms error
2Stratum 1 over network< 10 ms error
3–15Cascading NTP peersDegrading accuracy
16UnreachableOut of sync
VersionAuthEncryptionTrapInformExam Focus
v1Community stringNone✓ Unreliable (UDP)✗Legacy, risky
v2cCommunity stringNone✓ Unreliable✓ Reliable (ack'd)Common
v3Username + passwordAES/DES✓✓Secure, recommended
Operations:
  • Get — NMS reads MIB variable from device
  • Trap — Device pushes alert to NMS (unconfirmed)
  • Inform — Device pushes alert + waits for acknowledgment (v2c/v3 only)

Config: snmp-server community [ro|rw] + snmp-server trap-source `

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QoS — Key

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Sections in this topic

Nat PatDhcpDnsNtp Syslog