From ae1cfcfb197ffcbef8675913605e8db00215d363 Mon Sep 17 00:00:00 2001 From: cloin Date: Sat, 28 May 2022 04:01:42 +0000 Subject: [PATCH] Update 'selected/http_to_phy.md' --- selected/http_to_phy.md | 9 ++++++--- 1 file changed, 6 insertions(+), 3 deletions(-) diff --git a/selected/http_to_phy.md b/selected/http_to_phy.md index 618b3fa..191c246 100644 --- a/selected/http_to_phy.md +++ b/selected/http_to_phy.md @@ -161,10 +161,11 @@ Link speed negotiation (intel) NUC with two (usb) NICs -- VMs that would tag traffic with VLAN. Ethernet packet tagged with VLAN 1, - +``` | 1 1 1 1 1 1 1 2 | | 2i 2o | | 2 | | NUC | | 2 | | | +``` layer 2 ethernet -- hamachi / layer 3 ip -- openvpn @@ -177,7 +178,7 @@ Routers are layer 3 Home "router" is a router / switch combo Network Topology -- this is mostly outside my wheelhouse; infiniband/optics? - +``` "crossover cable" A B TX ---\/--- TX @@ -187,17 +188,19 @@ RX ---/\--- RX A B TX -------- TX RX -------- RX - +``` Switch maintains an ethernet routing table, uses mac addresses to determine which ports need to be routed to other ports TTL -- preventing packets from hopping forever on layer 3 connections, ICMP is a totally separate thing ICMP -- https://en.wikipedia.org/wiki/Internet_Control_Message_Protocol +``` SEND CHEESEBURGER TO GOOGLE A -> HR -> ISP -> | | | | -> GOOGLE subnet 192.168.1.X HR -> ISP | DESTINATION UNREACHABLE {ICMP 3} | TIME EXCEEDED {ICMP 11} TTL Expires +``` Blocking ICMP is messy, be careful! https://en.wikipedia.org/wiki/Black_hole_(networking)