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pathvector-dev

I build networking tools (netblame, pathwx) and write hands-on protocol labs — BGP to QUIC, all runnable with containerlab. Originals at blog.pathvector.dev

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Announce, withdraw, and peer down are three different code paths
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Announce, withdraw, and peer down are three different code paths

#python #network #bgp #protocol
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9 min read
When Loc-RIB changes, every peer needs a different answer
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When Loc-RIB changes, every peer needs a different answer

#python #network #bgp #protocol
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8 min read
Established is not a status label — it's a write permission
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Established is not a status label — it's a write permission

#python #network #bgp #protocol
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7 min read
One route, one function chain: reading a BGP pipeline as code
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One route, one function chain: reading a BGP pipeline as code

#python #network #bgp #protocol
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9 min read
When a BGP peer disappears, one session loss becomes many route decisions
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When a BGP peer disappears, one session loss becomes many route decisions

#python #network #bgp #routing
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8 min read
Export policy decides what leaves: reading BGP outbound state as code
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Export policy decides what leaves: reading BGP outbound state as code

#python #network #bgp #protocol
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7 min read
Import policy rewrites the route before best-path ever sees it
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Import policy rewrites the route before best-path ever sees it

#python #network #bgp #protocol
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8 min read
Validation State Doesn't Act By Itself
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Validation State Doesn't Act By Itself

#python #bgp #network #protocol
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6 min read
Origin validation is a separate decision from best path
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Origin validation is a separate decision from best path

#python #bgp #network #protocol
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7 min read
How a BGP UPDATE Changes State: Reading Withdrawal and Announcement as Code
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How a BGP UPDATE Changes State: Reading Withdrawal and Announcement as Code

#python #bgp #network #protocol
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6 min read
What a BGP Neighbor Needs — Reading Session Setup as Code
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What a BGP Neighbor Needs — Reading Session Setup as Code

#python #bgp #network #protocol
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7 min read
Split-Horizon DNS: One Name, Two Answers, and the Server Decides by Who's Asking
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Split-Horizon DNS: One Name, Two Answers, and the Server Decides by Who's Asking

#dns #bind #network #containerlab
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7 min read
DNS Round-Robin: The Cheapest Load Balancer Is Three A Records and a Rotating Answer
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DNS Round-Robin: The Cheapest Load Balancer Is Three A Records and a Rotating Answer

#dns #network #containerlab #bind
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7 min read
DNAT Explained: Publishing an Internal Service Through One Public Address and Port
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DNAT Explained: Publishing an Internal Service Through One Public Address and Port

#nat #network #containerlab #iptables
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7 min read
Policy Routing: When the Source Address Picks the Path, Not the Destination
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Policy Routing: When the Source Address Picks the Path, Not the Destination

#network #linux #containerlab #routing
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7 min read
TCP MSS Clamping: Fixing Path MTU Black Holes by Rewriting the SYN
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TCP MSS Clamping: Fixing Path MTU Black Holes by Rewriting the SYN

#tcp #network #containerlab #mtu
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7 min read
BFD Explained: Catching a Silent Network Failure in Under a Second
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BFD Explained: Catching a Silent Network Failure in Under a Second

#bfd #ospf #network #containerlab
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8 min read
OSPF Explained: Flood the Map, Run Dijkstra, and Reroute in Seconds
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OSPF Explained: Flood the Map, Run Dijkstra, and Reroute in Seconds

#ospf #network #containerlab #frr
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8 min read
ECMP Explained: Two Equal Paths, and the Kernel Hashes Flows Across Them
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ECMP Explained: Two Equal Paths, and the Kernel Hashes Flows Across Them

#bgp #network #containerlab #ecmp
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8 min read
CUBIC vs BBR: How Your Congestion Control Choice Changes Throughput 7x on a Lossy Path
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CUBIC vs BBR: How Your Congestion Control Choice Changes Throughput 7x on a Lossy Path

#tcp #network #containerlab #bbr
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8 min read
Traffic Shaping with a Token Bucket: Cap a 56 Gbit/s Link at 10 Mbit/s Using tc
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Traffic Shaping with a Token Bucket: Cap a 56 Gbit/s Link at 10 Mbit/s Using tc

#qos #network #containerlab #linux
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7 min read
Redirects and Cookies: How Stateless HTTP Fakes Having a Memory
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Redirects and Cookies: How Stateless HTTP Fakes Having a Memory

#http #network #containerlab #curl
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7 min read
Path MTU Discovery: Why Blocking ICMP Makes Big Pages Hang
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Path MTU Discovery: Why Blocking ICMP Makes Big Pages Hang

#mtu #icmp #network #containerlab
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8 min read
ARP Explained: How IPv4 Turns an IP Address into a MAC by Shouting at Everyone
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ARP Explained: How IPv4 Turns an IP Address into a MAC by Shouting at Everyone

#arp #network #containerlab #ipv4
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7 min read
DHCP Explained: How a Machine With No IP Address Gets One in Four Messages
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DHCP Explained: How a Machine With No IP Address Gets One in Four Messages

#dhcp #network #containerlab #udp
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7 min read
GRE Explained: The Layer-3 Tunnel That Wraps Everything and Encrypts Nothing
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GRE Explained: The Layer-3 Tunnel That Wraps Everything and Encrypts Nothing

#gre #network #containerlab #tunneling
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7 min read
How traceroute Really Works: TTL, ICMP Time-Exceeded, and Mapping a Path Hop by Hop
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How traceroute Really Works: TTL, ICMP Time-Exceeded, and Mapping a Path Hop by Hop

#network #icmp #traceroute #containerlab
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8 min read
VXLAN Explained: An Overlay You Can Read on the Wire
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VXLAN Explained: An Overlay You Can Read on the Wire

#vxlan #network #containerlab #overlay
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8 min read
WireGuard, Seen From Both Sides: The Same Ping as Ciphertext and Cleartext
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WireGuard, Seen From Both Sides: The Same Ping as Ciphertext and Cleartext

#wireguard #vpn #network #containerlab
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9 min read
Mutual TLS Explained: Making the Client Prove Its Identity Too
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Mutual TLS Explained: Making the Client Prove Its Identity Too

#tls #mtls #network #containerlab
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8 min read
DNSSEC in a Container Lab: Sign a Zone, Tamper With It, and Watch the Resolver Say No
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DNSSEC in a Container Lab: Sign a Zone, Tamper With It, and Watch the Resolver Say No

#dns #dnssec #network #containerlab
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11 min read
One Web Request, End to End: Watch curl Cross DNS, TCP, TLS, and HTTP in Order
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One Web Request, End to End: Watch curl Cross DNS, TCP, TLS, and HTTP in Order

#network #dns #tcp #tls
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9 min read
HTTP/1.1 in the Clear: Read One Request and Response Line by Line, Then Watch 304 Save the Day
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HTTP/1.1 in the Clear: Read One Request and Response Line by Line, Then Watch 304 Save the Day

#http #network #containerlab #caching
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8 min read
TLS 1.3 on the Wire: What an Eavesdropper Can Still See Before Encryption Kicks In
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TLS 1.3 on the Wire: What an Eavesdropper Can Still See Before Encryption Kicks In

#tls #network #containerlab #openssl
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8 min read
One TCP Connection, From SYN to FIN: Capture the Whole Lifecycle in tcpdump
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One TCP Connection, From SYN to FIN: Capture the Whole Lifecycle in tcpdump

#tcp #network #containerlab #tcpdump
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10 min read
DNS Caching Explained: Watch TTLs Count Down and NXDOMAIN Get Cached Too
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DNS Caching Explained: Watch TTLs Count Down and NXDOMAIN Get Cached Too

#dns #network #containerlab #bind9
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10 min read
A Network Protocol Learning Roadmap: 42 Hands-On Labs and 151 Code-Reading Sessions, Mapped
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A Network Protocol Learning Roadmap: 42 Hands-On Labs and 151 Code-Reading Sessions, Mapped

#network #protocol #roadmap #python
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3 min read
RPKI Origin Validation: Watch BGP Routes Turn Valid, Invalid, and Not Found
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RPKI Origin Validation: Watch BGP Routes Turn Valid, Invalid, and Not Found

#rpki #bgp #network #containerlab
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8 min read
Competing Origins: When Two ASes Announce the Same Prefix, Who Do You Believe?
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Competing Origins: When Two ASes Announce the Same Prefix, Who Do You Believe?

#bgp #network #containerlab #routeleak
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9 min read
BGP UPDATE in Action: Watch a Route Appear, Disappear, and Come Back
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BGP UPDATE in Action: Watch a Route Appear, Disappear, and Come Back

#bgp #network #containerlab #frrouting
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12 min read
BGP From Scratch: Announce One Prefix and Explain Every Field of the Route
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BGP From Scratch: Announce One Prefix and Explain Every Field of the Route

#bgp #network #containerlab #frr
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12 min read
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