Example 6-7 shows three equal-cost
default routes, forwarding traffic to three different gateways on the outside interface.
Example 6-7. Configuring ECMP (Equal Cost Multiple Path) Default Routes
hostname(config)# route outside 0.0.0.0 0.0.0.0 209.165.201.1
hostname(config)# route outside 0.0.0.0 0.0.0.0 209.165.201.2
hostname(config)# route outside 0.0.0.0 0.0.0.0 209.165.201.3
Note
ECMP is not supported across multiple interfaces.
Open Shortest Path First (OSPF)
Dynamic routing occurs when devices communicate to adjacent devices, informing each other of the reachability
of networks. These devices communicate using a routing protocol such as OSPF to exchange route information.
Unlike static routing, the routing information populated into the routing tables is added and deleted dynamically
by a dynamic routing protocol as routes change over time.
OSPF is an Interior Gateway Protocol (IGP) that distributes routing information among devices. OSPF is used
over IP, and OSPF packets are transmitted with an IP data packet with the protocol field in the IP header set to
89. OSPF uses a link-state algorithm to build and calculate the shortest path to all known destinations. The
algorithm used to calculate the shortest path is called the Dijkstra algorithm (named after its inventor Edsger
W.
Pages:
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283