Optimized Edge Routing (OER): Configuration Example

Introduction

Otimized Edge Routing (OER) also known as Performance Routing (PFR) ia an alternative way of routing traffic. OER/PfR selects a path based on the performance of the path and hence optimizing the connections. For example, an OER enabled edge router connected with two ISP can perform load sharing by transmitting data to 2nd ISP when it detect conjestion over 1st ISP link. OER/PfR can measure parameters such as delay, throughput, loss and reachability, among others, pre-determined policies to select the best performing path, and route packets accordingly.

OER has two components: a Master Controller (MC) and one or more Border Routers (BR). The Master Controller is the decision maker, whereas the border routers are edge routers with exit interfaces at the network edge. Border routers are either used to access the Internet or used as WAN exit links. OER communication between the master controller and the border routers is carried separately from routing protocol traffic. This communication is protected by Message Digest 5 (MD5) authentication. Each border router has both an external interface, which is connected, for example, to an ISP by a WAN link, and an internal interface that is reachable by the master controller.

Prerequisite

• Understanding of IP Routing Protocol
• CEF must be enabled on participating routers

Summary

In this document Router R1, R2 and R3 forms an OSPF neighbor relationshio (Area 0) and acting as internal network.

Router R1 from OER perspective being the Master Controller (MC) and the Border Router (BR). There could be scenarios where MC and BR are two different identities. However for simplicity I have choosen R1 to act as both i.e. MC and BR. The two components taks over TCP connection authenticated via MD5. Router R1 has redundant connection to R4 through interface (FastEthernet 1/0 and Serial 0/0).

Router R4 is the provider router which is injecting default route  0.0.0.0/0 into R1 via FastEthernet 0/0, making this path primary and  Serial 0/0 secondary path.

NOTE: All configurations are tested on Cisco 3745 Router operation on IOS Version 12.4(15)T14  Advance IP Services version.

Objective

1. Configure R1 as the OER Master Controller and Border Router.
2. FastEthernet 0/0 and FastEhetnet 0/1 interface of R1 are marked as Internal Interface.
3. FastEthernet 1/0 and Serial 0/0 interface of R1 are marked as External Interface.
4. Any ICMP traffic to 4.4.4.4/32 (Lo0 of R4) going from R1 should use the primary link (i.e through FastEthernet 1/0 interface of R1).
5. Any telnet traffic (port 19) to 44.44.44.44/32 (Lo1 of R4)going from R1 should use the secondary link (i.e through Serial 0/0 interface of R1).

Topology diagram

Configuration

R1-->MC and BR Configuration

key chain OER

key 1

   key-string CISCO

!

oer master

policy-rules OER

logging

!

border 1.1.1.1 key-chain OER

  interface Serial0/0 external

  interface FastEthernet1/0 external

  interface FastEthernet0/1 internal

  interface FastEthernet0/0 internal

!

learn

  periodic-interval 0

  monitor-period 1

no max range receive

mode route control

!

oer border

local Loopback0

master 1.1.1.1 key-chain OER

R1--> OER Policy Configuration

ip access-list extended ICMP-TRAFFIC

permit icmp any host 4.4.4.4

ip access-list extended TELNET-TRAFFIC

permit tcp any host 44.44.44.44 eq chargen

!

oer-map OER 10

match traffic-class access-list ICMP-TRAFFIC

set next-hop 172.14.14.4

!

oer-map OER 20

match traffic-class access-list TELNET-TRAFFIC

set next-hop 172.16.14.2

!

Note: For complete configurations, see attached text files (Config-R1, Config-R2, Config-R3, Config-R4).

Verification Commands

show oer master

Note: The output is truncated, for complete output of the command "show oer master" see attached file

show oer master border detail

show oer master traffic-class

References

Setting Up OER Network Components

Optimized Edge Routing Configuration Guide, Cisco IOS Release 12.4T

Attachments:

• R1-show oer master.txt.zip (791 bytes)
• Config-R1.txt.zip (985 bytes)
• Config-R2.txt.zip (582 bytes)
• Config-R3.txt.zip (550 bytes)
• Config-R4.txt.zip (626 bytes) 

Source: supportforums.cisco.com
 

Troubleshooting EIGRP Variance Command

Introduction

EIGRP provides a mechanism to load balance over unequal cost paths throungh Variance Command. Variance is a number (1 to 128), multiplied by the local best metric then includes the routes with the lesser or equal metric. The default Variance value is 1, which means equal-cost load balancing.

A condition, Feasibility Condition, must be met for all routes to be installed in routing table via Variance Command.

What is Feasibility Condition?

If, for a destination, a neighbour router advertises a distance that is stricktly lower than our feasible distance, then this neighbour lies on a loop free route to this destination.

Prerequisite

Understanding of EIGRP routing protocol

Topology Diagram

Background

In this document we are trying to understand the feasibility condition and the working of variance command. All routers depcited in the topology diagram are configured with EIGRP routing protocol. The Lo3 address (3.3.3.3/32) is redistributed in EIGRP via redistribute connected command under the EIGRP process.

Router R1 has three paths to the route 3.3.3.3/32

1. Path R1-R2-R3
2. Path R1-R4-R3
3. Path R1-R5-R3

Specifically, we have used different interface selection to provide unequal cost.

With default configuration, the route R1-R2-R3 is chosen over the others as the overall metric of this path is less as compared to that of the paths. Please see the output of the command "show ip route eigrp".

So far so good. Everything is working as expected.

As we desire, EIGRP with load balancing functionality, the route 3.3.3.3/32 should be available with R1 via R4 and R5. We verify the minimum and the maximum cost to reach 3.3.3.3 network from R1 via command "show ip eigrp topology all-links". R1 from its EIGRP topology table is learning the route 3.3.3.3/32 from all the sources but installed the route learned via neighbour R2 in its routing table.

The lowest metric is 435200 (that of path R1-R2-R3) and the maximum 2809856 (that of path R1-R5-R3).

Doing a small calculation to find the variance number, 2809856/435200 = 6.4567. I wil use a variance value of 7. Now 7*435200 = 3046400, routes with metric less than this value should be included.

On configuring command "variance 7" under EIGRP process, the route 3.3.3.3/32 now has two sources, R2 and R4. This can be verified by command "show ip route eigrp" on R1.

The output is not what we desired, the expected result was route 3.3.3.3 to be available from all the three neighbours i.e. R2, R4 and R5. Why the route from R4 was included and the route R5 discarded?

For R1 and R4

1. If, for a destination (3.3.3.3), a neighbour router (R4) advertises a distance (409600) that is stricktly lower than our feasible distance (435200), then this neighbour lies on a loop free route to this destination.
2. Metric learned from R4 (2323456) < Metric Calculated via Variance Multiplier (3046400)

For R1 and R5,  this condition is not met as R5 advertises a distance 2297856 which is much higher that the feasible distance (435200) on R1.

Note: Even though the overall metric from R5 (2323456) is less than the Metric Calculated via Variance Multiplier (3046400), the route 3.3.3.3 is discarded as it does not meet the Feasibility Condition.

Configurations

Please see attached files.

References

EIGRP Commands

Troubleshooting EIGRP

Cisco Support for EIGRP

Attachments:

• R5.txt.zip (267 bytes)
• R4.txt.zip (292 bytes)
• R3.txt.zip (384 bytes)
• R2.txt.zip (291 bytes)
• R1.txt.zip (324 bytes)  

Source: supportforums.cisco.com

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