- EIGRP
Enhanced Interior Gateway Routing Protocol (EIGRP)
EIGRP
From PacketLife.net
- OSPF
Open Shortest Path First (OSPF) is a link-state interior gateway protocol that routes Internet Protocol (IP) packets solely within a single autonomous system. OSPF uses a metric of cost based on the Shortest Path First algorithm to find the least-cost path to any destination in the network. Popular because of its scalability, fast convergence, and vendor-interoperability. In operation, each router using OSPF sends a list of its neighbors to other routers on the network. From this information, routers can determine the network design and the shortest path for data to travel.
- RIP
RIP is a widely-used protocol for managing router information within a self-contained network. It is a distance-vector routing protocol which employs the hop count as a routing metric. RIP prevents routing loops by implementing a limit of 15 hops on the number of hops allowed in a path from the source to a destination.
Using RIP, a gateway host sends its entire routing table to its closest neighbors. The neighbor host in turn will pass the information on to its next neighbor and so on until all hosts within the network have the same knowledge of routing paths, a state known as network convergence. The original specification required router updates to be transmitted every 30 seconds resulting in a huge traffic load on larger networks. Router authentication has been added to enable secure transmissions, and discovery was changed to a multicast method to reduce overall network traffic.
- Link state vs. distance vector vs. hybrid
Link state routing uses a shortest path algorithm providing a means of controlling the routing process and permitting routers to respond quicker to network changes. Common examples include NLSP, OSPF, and IS-IS.
Distance Vector routing uses hop count, examples include RIP, IGRP, and IPX RIP.
Hybrid routing is similar to distance vector with more accurate update metrics, examples include IS-IS and EIGRP.
- Static vs. dynamic
Static routing occurs when a router uses a manually-configured routing entry to forward traffic. This requires the manual input of the route table by a network administrator, is time consuming, and errors may occur.
The "route add" command adds a static route to the routing table. The "route add" command with the -p switch makes the static route persistent on a host machine
Dynamic routing is performed automatically. If a change occurs in the topology the dynamic routing protocol can re-calculate its route.
- Routing metrics
Routers use the lowest cost routes, routes that are the easiest and/or fastest, to reach a destination. The cost of a route is calculated using what is known as routing metrics. Routing metrics are assigned to routes by routing protocols to provide measurable values that can be used to determine how low cost a route will be.
- Next hop
- Spanning-Tree Protocol
- VLAN (802.1q)
- Port mirroring
- Broadcast domain vs. collision domain
- IGP vs. EGP
Interior Gateway Protocol (IGP) is a routing protocol that is used to exchange routing information within an autonomous system (AS).
Exterior Gateway Protocol (EGP) was the first TCP/IP exterior routing protocol for the Internet but is now considered somewhat obsolete. Routing was done using a small number of centralized core routers that maintained complete information about network reachability on the Internet. They exchanged information using the historical interior routing protocol, the Gateway-to-Gateway Protocol (GGP). Around the periphery of this core were located other non-core routers, sometimes standalone and sometimes collected into groups, that exchange network reachability information with the core routers using EGP.
- Routing tables
A routing table, or routing information base (RIB), is a data table stored in a router or a networked computer that lists the routes to particular network destinations, and in some cases, metrics (distances) associated with those routes. The routing table contains information about the topology of the network immediately around it. Before a data packet is forwarded, the routing table is reviewed to determine the best possible path for the data to reach its destination. The construction of routing tables is the primary goal of routing protocols. Maintaining an accurate routing table is essential for effective data delivery. Static routes are entries made in a routing table manually and are fixed rather than being the result of some network topology "discovery" procedure. Every computer on a TCP/IP network has a routing table stored locally.
- Convergence (steady state)
