Routing Tables

---

Unit: 5 Lesson: 1

what if i had a gps but for packets >:)

Most hosts on a network don't have the necessary capabilities on their NICs to perform routing. This is why each network has a device, aptly called a router, to do that job for it.

Routing Table Entries

Information on how each host is connected to the network, along with where to find other networks, is stored on the router in a routing table. Routing tables are usually populated using the EIGRP protocol. Each entry in the routing table has the following information:

• Protocol (the source of the route; either static or dynamic)
• Destination (can be defined as a specific host, but usually set to a Network ID)
• Interface (the local interface used to forward the packet along it's set route, either an IP address or a Layer 2 Interface ID)
• Gateway/Next Hop (the IP address of the next router that's responsible for forwarding the packet)

Entries are organized using four general categories: directly connected, remote routes, host routes, and default routes.

• Directly connected routes are routes that have a local interface.
• Remote routes are for subnets and IP networks that aren't directly connected.
• Host routes are specific IP addresses (v4 w/ a /32 prefix, v6 w/ a /128 prefix)
• Default routes are used when an exact match for a network or host route isn't found (usually set to 0.0.0.0/0 or ::/0)

Static routes are manually added to the routing table by the network admin, and can only be edited by the admin. It's only useful in certain circumstances, but if the routing topology changes frequently, it's not recommended, since every router that has that route will need to be manually updated. If a static route isn't even reachable, it's disabled by default.

Routing CLI Commands

Command	Description	Operating System
show route show ip route show ipv6 route	Print the active routing table.	Linux
route print	-	Microsoft-Windows
show arp show ip arp	Print the current MAC address cache table.	Linux
arp -a	-	Windows

#Netplus