HSRP (Hot Standby Routing Protocol)
by
10 / 100
Powered by Rank Math SEO
SEO Score

HSRP (Hot Standby Routing Protocol) – Simple Explanation

  • HSRP = Hot Standby Routing Protocol
  • Cisco ka gateway redundancy protocol hai.
  • Network me 2 routers hotay hain →
    ✔ 1 Active
    ✔ 1 Standby
  • Normal me traffic Active router se jata hai.
  • Agar Active router down ho jaye → traffic Automatically Standby router par shift ho jata hai.
  • Jab Active wapas aata hai → traffic wapas automatically use par chala jata hai.

🔥 Real Problem (Without HSRP)

PCs me sirf 1 gateway set hota hai.
Agar woh gateway down ho jaye, traffic shift nahi hoga.
Gateway manually change karna padega.

🔥 Solution = HSRP

HSRP ek virtual gateway IP create karta hai.
Sare PCs isi virtual IP ko gateway banate hain.
Agar koi router down ho jaye → traffic automatically dusre router par shift ho jata hai.

⭐ ACL (Access Control List) – Simple Explanation

ACL = Rules jo router ko batati hain kis traffic ko allow karna hai, aur kis ko block.

  • Layer 3 security
  • Packet filtering firewall
  • Traffic control allow/deny rules

⭐ Types of ACL

1️⃣ Standard ACL

  • Number: 1 – 99
  • Sirf Source IP check karta hai
  • Pura network/host block kar sakta hai
  • Destination ke paas (closest to destination) apply hota hai

2️⃣ Extended ACL

  • Number: 100 – 199
  • Check karta hai:
    ✔ Source IP
    ✔ Destination IP
    ✔ Protocol (TCP/UDP/ICMP)
    ✔ Port number (80, 21, 22, etc.)
  • Specific service block kar sakta hai
  • Source ke paas apply hota hai

⭐ Important ACL Terms

  • Deny → Block
  • Permit → Allow
  • Inbound → Router me enter hone wala traffic
  • Outbound → Router se bahar jaane wala traffic
  • Implicit deny → Last me hidden “deny all” hota hai

⭐ ACL Rules (Very Important)

  • Pehle saare deny likho
  • Kam se kam 1 permit rule zaroor hona chahiye
  • ACL sequentially kaam karta hai
  • Ek interface par per direction 1 ACL lag sakti hai

⭐ Basic ACL Commands

✔ Standard ACL

access-list <no> <permit/deny> <source> <wildcard>
interface <int>
ip access-group <no> in/out

✔ Extended ACL

access-list <no> <permit/deny> <protocol> <src> <src-wildcard> <dst> <dst-wildcard> <operator> <port>
interface <int>
ip access-group <no> in/out

⭐ Standard ACL Lab – Simple Summary

Objective

  • Block 192.168.1.2 → 172.16.1.2
  • Block 192.168.1.3 → 172.16.0.0 network

ACL

access-list 1 deny host 192.168.1.2
access-list 1 deny host 192.168.1.3
access-list 1 permit any

Apply

int fa0/1
ip access-group 1 out

⭐ Telnet ACL (Only 192.168.1.0 Allowed)

access-list 1 permit 192.168.1.0 0.0.0.255
line vty 0 4
access-class 1 in

⭐ Extended ACL Lab – Short Summary

1) Block HTTP (port 80)

access-list 100 deny tcp host 192.168.1.2 host 192.168.2.2 eq 80
access-list 100 deny tcp host 192.168.1.3 host 192.168.2.3 eq 80

2) Block FTP (port 21)

access-list 100 deny tcp 192.168.1.0 0.0.0.255 host 192.168.2.2 eq 21

3) Block ICMP

access-list 100 deny icmp 192.168.1.0 0.0.0.255 host 192.168.2.3 echo
access-list 100 deny icmp 192.168.1.0 0.0.0.255 host 192.168.2.3 echo-reply

4) Permit Everything Else

access-list 100 permit ip any any

Here is your entire content rewritten in super short, simple, clear Hinglish — perfect for notes, PDF, teaching, or YouTube script.

⭐ Short + Simple + Clear Version

✅ Apply ACL on Interface (Inbound)

R1(config)# int fa0/1
R1(config-if)# ip access-group 100 in

⭐ Named ACL (Easy Editing Version)

Create Named Extended ACL

R1(config)# ip access-list extended ABC
R1(config-ext-nacl)# deny tcp host 192.168.1.2 host 192.168.2.2 eq 80
R1(config-ext-nacl)# deny tcp host 192.168.1.3 host 192.168.2.3 eq 80
R1(config-ext-nacl)# deny tcp 192.168.1.0 0.0.0.255 host 192.168.2.2 eq 21
R1(config-ext-nacl)# deny icmp 192.168.1.0 0.0.0.255 host 192.168.2.3 echo
R1(config-ext-nacl)# deny icmp 192.168.1.0 0.0.0.255 host 192.168.2.3 echo-reply
R1(config-ext-nacl)# permit ip any any

Apply Named ACL

R1(config)# int fa0/1
R1(config-if)# ip access-group ABC in

Show ACL

R1# show access-lists

⭐ Remove a Single ACL Entry (Example: Sequence 50)

R1(config)# ip access-list extended ABC
R1(config-ext-nacl)# no 50

⭐ Router Password Recovery (Super Short)

  1. Console connect
  2. Open HyperTerminal
  3. Power ON router
  4. Press CTRL + SHIFT + BREAK → ROMMON mode
  5. Type:

Modular router:

confreg 0x2142
reset

Fixed router:

o/r 0x2142
i
  1. Router boots without password
  2. Do:
enable
copy start run
  1. Change passwords
  2. Set register back:
config-register 0x2102
write
reload

⭐ DHCP (Short & Clear)

DHCP = Host ko auto IP assign karta hai.

Commands:

ip dhcp excluded-address 192.168.1.50
ip dhcp pool cisco
network 192.168.1.0 255.255.255.0
default-router 192.168.1.1

⭐ APIPA (Super Easy Meaning)

  • DHCP server na mile to Windows khud IP assign karta hai.
  • Range: 169.254.0.1 – 169.254.255.254
  • Subnet: 255.255.0.0
  • Self-created IP tab tak use hoti hai jab tak DHCP server mil nahi jata.
  • Small networks (25 clients tak) ke liye useful.

⭐ NAT – Network Address Translation (Very Short)

NAT = Private IP → Public IP translation

Why required?

  1. Public IP shortage
  2. Hide internal network

Private IP ranges:

  • 10.0.0.0 – 10.255.255.255
  • 172.16.0.0 – 172.31.255.255
  • 192.168.0.0 – 192.168.255.255

Important Terms

  • Inside Local = Private IP
  • Inside Global = Public IP
  • Outside Local = Outside IP as seen by inside network
  • Outside Global = Original outside public IP

⭐ Types of NAT

1️⃣ Static NAT (1-to-1)

ip nat inside source static <privateIP> <publicIP>

2️⃣ Dynamic NAT (Pool se allocate hota hai)

access-list <no> permit <net> <wcm>
ip nat inside pool name <startIP> <endIP> netmask <mask>
ip nat inside source list <no> pool name

3️⃣ PAT (NAT Overload) — MOST COMMON

  • Many private IP → One public IP
  • Port numbers use karta hai
  • Isse hum sab internet use kar paate hain ek IP par
access-list <no> permit <net> <wcm>
ip nat inside pool name <start> <end> netmask <mask>
ip nat inside source list <no> pool name overload

NAT Interface Config

int s0
ip nat outside
int e0
ip nat inside

Leave a Comment