đŸ“Ļ MTU Path Discovery & Fragmentation Analyzer

Calculate effective MTU after encapsulation overhead, visualize fragmentation, and troubleshoot PMTUD issues

🏗ī¸ Encapsulation Stack (Drag to reorder)

No encapsulation layers added. Add a layer below to see how it affects MTU.
Effective Payload MTU
1500
bytes available for data
Not saved
📖 How to Use This Tool â–ŧ
  • Quick Start: Click a preset button (Internet, PPPoE, Azure, etc.) to load common scenarios
  • Custom Calculation: Set your Base MTU and add encapsulation layers one at a time
  • Results: See your effective payload MTU, recommended TCP MSS, and overhead breakdown
  • Fragmentation: If MTU < 1500, a visual fragmentation diagram appears automatically
  • Troubleshooting: Use the PMTUD flowchart to diagnose Path MTU Discovery issues
  • Performance Impact: The bandwidth waste calculator shows the real cost of fragmentation

MTU Calculation Results

Effective Payload MTU
1500
bytes available for data
Total Overhead
0
bytes consumed
Recommended TCP MSS
1460
MTU - 40 (IP+TCP headers)
Base MTU: 1500 bytes
Encapsulation Overhead: 0 bytes
Effective MTU: 1500 bytes
IP + TCP Headers: 40 bytes (20 IP + 20 TCP)
Maximum TCP Payload: 1460 bytes
Efficiency: 97.3%

💸 Bandwidth Waste Calculator

ℹī¸ Performance Impact: Calculate the real cost of fragmentation on your network bandwidth.

🔍 Path MTU Discovery (PMTUD) Interactive Troubleshooter

ℹī¸ Interactive Flowchart: Click through the diagnostic steps below to troubleshoot PMTUD issues.
🚀 Start: Having packet loss or slow performance?
Click to begin the diagnostic process. We'll walk through systematic troubleshooting steps.

🔧 Configuration Examples

ℹī¸ TCP MSS Clamping: Configure these on your routers to prevent fragmentation.
! Cisco IOS/IOS-XE
interface GigabitEthernet0/0
ip tcp adjust-mss 1460
! Juniper JunOS
set interfaces ge-0/0/0 unit 0 family inet mtu 1500
set interfaces ge-0/0/0 unit 0 family inet tcp-mss 1460
# Linux iptables
iptables -t mangle -A FORWARD -p tcp --tcp-flags SYN,RST SYN -j TCPMSS --set-mss 1460

🚀 Jumbo Frame Analysis

ℹī¸ Jumbo Frames: Larger MTU sizes improve throughput for storage and datacenter networks.
Standard Frame Efficiency: 97.3% (1460/1500)
Jumbo Frame (9000 MTU): 99.6% efficiency (8960/9000)
Frames per GB (Current): ~731,000 frames
Frames per GB (Jumbo 9000): ~119,000 frames (84% reduction)
CPU Savings (Jumbo vs Std): ~84% fewer interrupts

Recommendations:

  • Standard 1500 MTU: Internet, general campus networks, mixed environments
  • Baby Jumbos (2000): Metro Ethernet, some MPLS networks
  • Jumbo Frames (9000): iSCSI, NFS, server-to-server, datacenter fabrics
  • Super Jumbos (9216): Storage networks, 10GbE+ datacenter