S6-C9 - Backup To protect mission critical applications

Backup Links Dialup technologies –Interface stays shutdown until one of two things happens to the primary link: The primary goes down Primary link reaches an administratively defined load The primary link is typically a Frame Relay PVC or a leased line. Backup (secondary )interfaces can be a physical or a logical interface such as a dialer interface. – BRIs, asynchronous interfaces, and dialer interfaces. Backups best configured with dialing profiles

Configuring Backup Interface Configure only one side of connection – usually headquarters Select the primary interface, and configure it as needed (for dial-on-demand routing, Frame Relayinterfaces and subinterfaces, X.25, and so on) –Router(config)#interface serial 0 Specify backup interface (on primary int) –outer(config-if)#backup interface interface-type number Define waiting period to bring up backup –Router(config-if)#backup delay{enable-delay | never} {disable-delay | never}

Floating Static Routes An alternative backup procedure Set static route with administrative distance larger than any dynamic routing protocol –ip route Disadvantages to a static route –The route is only used as a backup. It cannot be used for any other purpose. –Ineffective if the primary link is flapping (going up and down at a fast rate).

Overload Backup Monitor primary line over a five-minute period with 5 second sampling intervals Select primary line interface and configure as needed –Router(config)#interface S0 Specify backup interface –Router(config-if)#backup interface bri0 Set traffic load threshold –{enable-threshold | never}{disable-threshold | never} Note: The backup load command cannot be configured for Frame Relay subinterfaces.

Backup Example (config-if)#backup load 60 5 –backup interface (BRI0) becomes active when the primary interface reaches a load threshold of 60 percent or higher. –secondary line deactivates after the combined total traffic load on both lines drops to 5 percent of the capacity of primary link

Standby Mode backup interface is effectively shut down until enabled when the primary interface failing or passing a defined load threshold The primary link in Figure is the only route appearing in the routing table – the router continues to monitor the following two events: Carrier detect Keepalives When router loses carrier detects or keepalives, activates backup –routing table now reflects the backup route as the only route between the two sites

Dialer Profiles as Backup Interfaces BRI connection can be used to back up the primary Frame Relay link. It can be configured for DDR for the connection between locations. Configure one dialer interface to act as the backup line (in standby mode until engaged.) Configure another dialer profile for DDR between Central Site and Branch Make the physical BRI interface a member of both dialer pools. When you use a BRI for a dial backup, neither of the B channels can be used while the interface is in standby mode.

Configuring Dial Backup *Create and configure a dialer interface *Make the interface to be used as backup a member of the dialer pool by using the dialer pool member number command *Configure the primary interface to use a backup interface by going to the primary interface's configuration mode. Specify the backup interface dialer to be used with the backup interface dialer number command

Backup with OSPF Routing When the OSPF interface costs for the primary and secondary links are unequal, you can configure the costs to be the same by using the following command: – Router(config-if)#ip ospf cost interface-cost – OSPF's cost can be a value in the range from 1 to

Backup with EIGRP Routing use the variance command with a multiplier of 2: – Router(config)#router eigrp 1 – Router(config-router)#variance 2 –The variance multiples (2) times the lowest metric (2) increases the minimum allowable metric to 40 (2 * 20 = 40). EIGRP considers all the routes that have a metric under 40 as feasible successors