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CCNP ROUTE Command Guide: Implementing Path Control


  1. Offset Lists
  2. Cisco IOS IP Service Level Agreements
  3. Policy Routing Using Route Maps
  4. Configuration Example: Route Maps

Chapter Description

This chapter helps you prepare for the CCNP ROUTE exam by covering the following topics related to implementing path control: Offset lists, Cisco IOS IP Service Level Agreements, and Policy routing using route maps. It also uses route maps as a Configuration example.

Cisco IOS IP Service Level Agreements

Figure 5-1 shows the network topology for the configuration that follows, which shows the use of Cisco IOS IP SLA functionality for path control.

Figure 5-1

Figure 5-1 Cisco IOS IP Service Level Agreements

Customer requirements:

  • Customer A is multihoming to ISP-1 and ISP-2.
  • The link to ISP-1 is the primary link for all traffic.
  • Customer A is using default routes to the ISPs instead of BGP.
  • Customer A is using static routes with different administrative distances to make ISP-1 the preferred route.

Potential problem: If ISP-1 is having uplink connectivity problems to the Internet, Customer A will still be sending all of its traffic to ISP-1, only to have that traffic lost.

Solution: IOS IP SLA will be used to announce conditionally the default route to ensure reachability of a specific destination.

Follow these steps to configure Cisco IOS IP SLA functionality:

  • Step 1. Define one (or more) probes.
  • Step 2. Define one (or more) tracking objects.
  • Step 3. Define the action on the tracking object(s).
  • Step 4. Verify IP SLA operations.

Step 1: Define One (or More) Probes

R1(config)#ip sla monitor 22

Begins configuration for an IP SLA operation and enters SLA monitor configuration mode. 22 is the operation number and is a number between 1–2147483647.

R1(config-sla-monitor)#type echo protocol ipIcmpEcho source-interface fastethernet 0/0

Defines an ICMP Echo operation to destination address through source interface of FastEthernet 0/0 and enters ICMP Echo configuration mode.

R1(config-sla-monitor-echo)#frequency 10

Sets the rate at which the operation repeats. Measured in seconds from 1–604800 (7 days).


Exits IP SLA Monitor ICMP Echo configuration mode and returns to global configuration mode.

R1(config)#ip sla monitor schedule 22 life forever start-time now

Sets a schedule for IP SLA monitor 22. Packets will be sent out immediately and will continue forever.

Step 2: Define One (or More) Tracking Objects

R1(config)#track 1 sla 22 reachability

Configures the tracking process to track the reachability of IP SLAs operation 22.

Step 3: Define the Action on the Tracking Object(s)

R1(config)#ip route 3 track 1

Announces a default route to with an administrative distance of 3 if the tracking object 1 is true.

Step 4: Verify IP SLA Operations

R1#show ip sla configuration

Displays SLA components such as frequency, target address, scheduling, and other parameters.

R1#show ip sla statistics 22

Displays number of successful and failed probes, last operation, start time, and last return code for SLA monitor 22.

R1#show ip sla statistics 22 detail

Displays more in-depth output for SLA monitor 22.

3. Policy Routing Using Route Maps | Next Section Previous Section