Cisco CCNA Training Curriculum Snapshot Routing in a Dial on Demand Routing Environment

Why Snapshot Routing? Allows for routing protocols to exchange updates as they normally would Eliminates the need for static routes, which are difficult to maintain as the network grows

Overview Best suited for networks with data transfer sessions lasting longer than 5 minutes Compatible with the following distance-vector protcols: RIP IGRP RTMP (Appletalk Novell RIP, SAP, IPX RTP (Banyan Vines)

Overview Designed for a client/server relationship Client routers determine the frequency of the update exchanges Well suited for hub and spoke topology, such as a DDR environment Not compatible with link-state routing protocols such as EIGRP and OSPF These protocols depend on frequent sending of hello messages to discover neighboring routers in order to maintain routes

How Snapshot Routing works Allows routing updates to occur during an “active” period and suppresses updates during a “quiet” period It takes a “snapshot” of the routing tables to use during the quiet period

How Snapshot Routing works The “server” router, which is normally connected to the corporate network, determines the length of the active period The “client” router, usually the telecommuter, determines the length of the quiet period

How Snapshot Routing works During an active period, a client router dials the server router to get updates for its routing tables. The active period is at least 5 minutes and can be up to 100 minutes. Active Period Time (minutes)

How Snapshot Routing works During a quiet period, the routing tables are frozen until the next active period. The quiet period can be up to 65 days long. Active Period Active Period Quiet Period Time (minutes)

How Snapshot Routing works If the line is not available when the router transitions to an active period (for whatever reason), it enters a retry period (8 minutes long). The router continually attempts to connect until it enters an active period. Active Period Active Period Quiet Period Time (minutes) Active Period Retry Period

How Snapshot Routing works By default, snapshot routing allows updates over connections that are established for user data transfer. Snapshot routing can be configured to prevent update exchanges during user data transfer session, and the client router will dial the server router in the absence of normal traffic.

Summary Using snapshot routing in a DDR environment eliminates the need for static routing tables. Dynamic routing protocols are supported by allowing updates during a active period; bandwidth is preserved by suppressing updates during a quiet period. Updates can be prevented during user data transfer periods, and the client can be configured to dial the server during the absence of normal traffic.

Configuring Configure the server router Specify an interface Configure the server router Router(config)#int bri0 Router(config-if)#snapshot server active-time [dialer] active-time – amount of time, in minutes, of the active period (should be the same as the client) [dialer] – Allows the client router to dial the server router in absence of regular traffic

Configuring Configure the client router Specify an interface Configure the client router Router(config)#int bri0 Router(config-if)#snapshot client active-time quiet-time [suppress-statechange-updates] [dialer] Router(config-if)#dialer map snapshot sequence-number dial-string

Configuring Router(config)#int bri0 Router(config-if)#snapshot client active-time quiet-time [suppress- statechange-updates] [dialer] Router(config-if)#dialer map snapshot sequence-number dial-string active-time – amount of time, in minutes, of the active period (should be the same as the client) quiet-time – amount of time, in minutes, of the quiet period [suppress-statechange-updates] – prevents routers from exchanging updates during user data transfer sessions [dialer] – Used if the client router has to dial the server router in absence of regular traffic

Configuring Monitoring snapshot routing and DDR connections show dialer [interface type number] show isdn status show ip interface brief show snapshot interface

Snapshot Routing Lab