Quickly inspect and understand the kernel routing table using the classic Linux `route` command. 16.11.2025 | reading time: 3 min On a Linux system the `route` command shows the kernel routing table and answers the simple but crucial question: where will packets go? This short guide will show a real `route` session, explain the columns, and point to practical follow-ups so you can diagnose connectivity quickly. Real session: `route -n` Try this on a machine to see a concrete routing table snapshot: ```$ route -n Kernel IP routing table Destination Gateway Genmask Flags Metric Ref Use Iface 0.0.0.0 192.0.2.1 0.0.0.0 UG 100 0 0 eth0 192.0.2.0 0.0.0.0 255.255.255.0 U 0 0 0 eth0 203.0.113.5 192.0.2.254 255.255.255.255 UH 0 0 0 eth1 ``` Study that output: default route, connected network, and a host route appear immediately. Read the columns at a glance Look left to right: "Destination" is the target network or host, "Gateway" shows the next hop, "Genmask" gives the netmask, "Flags" encode state (U = up, G = uses gateway, H = host route), "Metric" is route cost and "Iface" names the outgoing interface; using `-n` avoids DNS delays so you see raw IPs and interpret routing behavior faster. Demonstrate adding and removing routes On a test box add or remove transient routes to observe effects: ```$ sudo route add -net 198.51.100.0 netmask 255.255.255.0 gw 192.0.2.254 $ route -n ...now the new network entry appears... $ sudo route del -net 198.51.100.0 netmask 255.255.255.0 ``` Use this workflow to verify path selection and to test failover or policy routing in simple setups. Options and gotchas to remember Useful switches are `-n` for numeric, `-A inet` to pick address family, and `-C` on some systems to consult cached info; note that `route` manipulates the kernel table directly but belongs to the older net-tools suite and may not reflect higher-level policy routing setups handled by iproute2, and changes via `route` are not persistent across reboots. Complementary commands worth running Pair `route` with `arp` to check neighbor resolution, with `traceroute` to follow a path hop by hop, and with `ip route` for the modern, more expressive view; that combination helps move from observation to diagnosis quickly. Wrap-up and next steps The `route` command gives a fast, pragmatic view into where Linux will send packets and is excellent for quick checks and teaching routing basics; to go deeper, practice on different topologies and compare `route` output with `ip route` to master modern routing tools and prepare for certifications such as CompTIA Linux+ or LPIC-1 using intensive exam preparation at bitsandbytes.academy. Join Bits & Bytes Academy First class LINUX exam preparation. network utilities troubleshooting
