OER – Optimized Edge Routing

  • Formally called as “Performance Routing” (PfR).
  • Takes into account the performance statistics from the edge/border router and route dynamically based on statistics like bandwidth, delay, jitter etc.
  • Can influence both incoming and outgoing traffic
  • Master controller: (MC)
    • Collects statistical information and uploads policy decision to border routers.
  • Border Routers: (BR)
    • Located at the edge of the network which collects and applies the policy from MC
  • A router can act both as MC and BR at the same time.


  • Profile Phase: Classifying the traffic to control .Can be automatic (via Netflow) or defined.
  • Measure phase: BRs collect statistics and reports to MC. It can be either by Passive (interface stats, netflow) or active (IP SLA) method.
  • Apply policy phase: Thresholds of performance value defined. MC uses this value and identify classes or links that are out of policy (OOP)
  • Control Phase:  MC can be configured to inject static routes or change metric
  • Verify Phase: To make sure the changes has brought the network In policy.


  • Identify an MC and configure key-chain. All messages between MC and BR will be encrypted.
  • “oer master” command to enable MC.
  • Configure border routers (using BR’s loopback IP) along with keychain. Also configure internal and external interfaces of that border router using “interface x/y [internal | external]”
  • On the border routers, configure key-chain and enable “oer border” command.
  • Configure local interface as loopback and the master IP address.
  • “show oer master” / “show oer border”
  • Profile phase:
    • Configure MC to learn about traffic classes by either dynamic (netflow) or static.
    • Traffic classes that are profiled are saved in Monitored traffic classes (MTC) table in MC.
    • “learn” command to allow MC to use Netflow Top talker feature to identify prefixes that uses highest throughput or delay ( if “throughtput” and “delay” CLI are configured)
    • Application traffic classes can be monitored using “protocol” command (NBAR)
    • Prefix traffic classes can also be configured manually using “oer-map” and “policy-rules”
  • Measure phase:
    • BR monitor actively/passively about traffic classes. Also monitor the load/traffic loss on external links.
    • Active probe: IP SLA (using “active-probe” command). Passive probe: Netflow.
    • Traffic classes are mapped to one of the below states:
    • Default:  Traffic is not under OER control.
    • Choose exit: OER is attempting to select an interface based on performance.
    • Hold down: MC request one of the BRs to monitor the traffic class using active probes.
    • In-Policy: Traffic is passed via an external link which satisfies default/configured policy.
    • Out-of-Policy (OOP): No exits conform to policy. MC has to select best possible exit.
  • Policy Phase:
    • Threshold values can be defined globally or prefix-specific using oer-map
    • Timers are used to avoid frequent change in exit-interface due to OER.
  • Control Phase:
    • Optional phase. OER changes the flow of traffic based on measurement.
    • “mode route change” command on MC allows it to instruct BRs to control the routing.
    • Changes are initiated when;
      • Traffic class or exit interface goes OOP
      • Periodic timers are expired and traffic classes are in “choose exit” state.
    • Changes can be done using below options;
      • IGP metric change, BGP attributes change, router injection or PBR introduction.
  • Verify Phase:
    • To check whether all traffic classes are brought In-policy.
    • Netflow is used in verify phase.

Sample config:

<on MC>

R0#show run | sec oer
key chain oer
 key 1
   key-string key1
oer master
 policy-rules cloud1
 border key-chain oer
  interface FastEthernet0/0 internal
  interface FastEthernet0/1 external
  interface FastEthernet1/0 external
  protocol tcp
 mode route control
 mode route metric bgp local-pref 110
oer-map cloud1 10
 match ip address prefix-list cloud1
 set delay threshold 10000
R0#show oer master border
Border           Status   UP/DOWN             AuthFail          ACTIVE   UP       00:10:16          0

<on BR>

R1#show run | sec oer
key chain oer
 key 1
   key-string key1
oer border
 local Loopback0
 master key-chain oer

Reference: http://www.cisco.com/en/US/docs/ios/oer/configuration/guide/12_4t/oer_12_4t_book.html

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