Static Routing Lab

Step 1 — How Routing Works

# A router looks at the destination IP and finds the BEST match in its routing table
# "Best match" = most specific (longest prefix)

# Routing table example:
C  192.168.1.0/24 is directly connected, Gi0/0
S  10.0.0.0/8    [1/0] via 192.168.2.1
S* 0.0.0.0/0     [1/0] via 203.0.113.1    ← default route (matches everything)

# Packet to 10.5.6.7:
# Match 10.0.0.0/8 → send to 192.168.2.1

# Packet to 8.8.8.8 (Google DNS):
# No specific match → use default route → send to 203.0.113.1

# Administrative Distance (AD) — lower = more trusted:
# Connected  = 0   (most trusted)
# Static     = 1
# EIGRP      = 90
# OSPF       = 110
# RIP        = 120

Step 2 — Lab Topology

PC1 (192.168.1.10)
  |
[Gi0/0] R1 [Gi0/1] ---10.0.12.0/30--- [Gi0/0] R2 [Gi0/1]
192.168.1.1                                         192.168.2.1
                                                        |
                                                    PC2 (192.168.2.10)

# Goal: PC1 should reach PC2 and vice versa
# R1 needs a route to 192.168.2.0/24
# R2 needs a route to 192.168.1.0/24

Step 3 — Next-Hop Static Route

# Configure interfaces first
! R1
interface GigabitEthernet0/0
 ip address 192.168.1.1 255.255.255.0
 no shutdown
interface GigabitEthernet0/1
 ip address 10.0.12.1 255.255.255.252
 no shutdown

! R2
interface GigabitEthernet0/0
 ip address 10.0.12.2 255.255.255.252
 no shutdown
interface GigabitEthernet0/1
 ip address 192.168.2.1 255.255.255.0
 no shutdown

# Add static routes (next-hop method)
! R1: to reach 192.168.2.0/24, send to R2's IP
ip route 192.168.2.0 255.255.255.0 10.0.12.2

! R2: to reach 192.168.1.0/24, send to R1's IP
ip route 192.168.1.0 255.255.255.0 10.0.12.1

# Syntax: ip route NETWORK MASK NEXT-HOP

Step 4 — Exit-Interface Static Route

# Alternative: specify outgoing interface instead of next-hop IP
ip route 192.168.2.0 255.255.255.0 GigabitEthernet0/1

# Or combine both (recommended on point-to-point links):
ip route 192.168.2.0 255.255.255.0 GigabitEthernet0/1 10.0.12.2

# Next-hop only = best practice on Ethernet (router must ARP)
# Exit-interface only = best practice on point-to-point (Serial links)

Step 5 — Default Route

# Default route = "send all unknown traffic here"
# Used to reach the internet or upstream router
ip route 0.0.0.0 0.0.0.0 203.0.113.1   # ISP gateway

# Show in routing table as S*:
S*  0.0.0.0/0 [1/0] via 203.0.113.1

# Propagate default route to OSPF/EIGRP neighbours
router ospf 1
 default-information originate   # sends default route to OSPF peers

Step 6 — Floating Static Route

# A backup static route that only activates when the primary goes down
# Give it a HIGHER AD than the primary

# Primary route via OSPF (AD 110) — auto-installed
# Backup static route — AD 200 (higher than OSPF, so not used unless OSPF fails)
ip route 192.168.2.0 255.255.255.0 10.0.99.1 200

# The "200" at the end is the Administrative Distance
# When OSPF route disappears, this static route (AD 200) takes over

# Common AD values for floating statics:
# Backup to OSPF (110)  → use 200
# Backup to EIGRP (90)  → use 100
# Backup to RIP (120)   → use 130

Step 7 — Verify & Troubleshoot

# Show routing table
show ip route
show ip route static    # only static routes

# S = static, S* = default route
S    192.168.2.0/24 [1/0] via 10.0.12.2

# Test connectivity
ping 192.168.2.10
ping 192.168.2.10 source 192.168.1.1   # ping FROM a specific interface

# Trace the path
traceroute 192.168.2.10

# Common issues:
# No route → missing ip route command
# One-way ping → return route missing on other router
# Correct route present but ping fails → check interface is "up/up"
show ip interface brief   # verify all interfaces are up

📋 Static Routing Cheat Sheet