TOPIC NETWORKING
Routing how packets find their way
IN 10 SECONDS
Routers inspect the destination IP of incoming packets and consult routing tables to determine the next hop. BGP handles internet-level routing; OSPF handles internal networks.
GOTCHA Asymmetric routing occurs when packets take one path to the server and a different path back, which can trigger firewall drops.
HOW A HOPS LOOKUP FLOWS
01 Host sends a packet. If destination is external, it goes to the default gateway router.
02 Router checks destination IP against its routing table for the longest prefix match.
03 Next Hop router forwards the packet to the next adjacent router interface.
04 Hop count TTL is decremented by 1 at each hop. If TTL hits 0, the packet is dropped.
POKE IT YOURSELF
route -n — view the system routing table
traceroute 8.8.8.8 — trace the hops packets take to Google
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