5.5 Static and Default Routing
5.5.8 Snapshot routing
With snapshot routing, the router is configured for dynamic routing. Snapshot routing controls the update interval of the routing protocols. Snapshot routing works with the following distance vector protocols:
  • Routing Information Protocol (RIP) for IP
  • Interior Gateway Routing Protocol (IGRP) for IP
  • Routing Information Protocol (RIP) and Service Advertisement Protocol (SAP) for Novell Internet Packet Exchange (IPX)
  • Routing Table Maintenance Protocol (RTMP) for AppleTalk
  • Routing Table Protocol (RTP) for Banyan VINES

Under normal circumstances, these routing protocols broadcast updates every 10 to 60 seconds, so an ISDN link would be made every 10 to 60 seconds simply to exchange routing information. From a cost perspective, this frequency is prohibitive. Snapshot routing solves this problem.

The goal of snapshot routing is to allow routing protocols to exchange updates as they normally would. Because Enhanced IGRP and link-state routing protocols, such as Novell Link Services Protocol (NLSP), Open Shortest Path First (OSPF), and Intermediate System-to-Intermediate System (IS-IS) depend on the frequent sending of hello messages to neighboring routers in order to discover and maintain routes, they are incompatible with snapshot routing.

Note: Snapshot routing is available in Cisco IOS Software Release 10.2 or later.