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Routing issue in MPLS VPN

Problem context & Scenario description -

We have recently implemented MPLS IP VPN with AT&T. We have 3 main offices and 10 other branch offices world wide and they all are connecting to AT&T MPLS VPN either via frame-relay or ATM ePVC. AT&T routes various subnets of 10/8 like 10.222.0.0/16 for boston office, 10.219.0.0/16 for California office, 10.210.0.0/16 for India office and similarly other /16 subnets for branch offices. We run BGP between our edge router and with AT&T edge router at each location. However, we have kept one IPLC line as a back up between India office and US Boston office. We want to automate the failover to this IPLC each time there is an issue on MPLS VPN from India. As you might be aware that recently there was a huge outage in Asia pac region due to Taiwan earthquake, at that time there were major routing issues in ATT network due to which our traffic from India office could not reach US offices via Asia PAC AS. Similar problem happened few days back also when AT&T ran into routing issues in their network and our India traffic to/from US could was lost inside the at&t network.

Problem is that during such routing issue at&t keep advertising our /16 subnets from their AS and those routes do not get evaporated from routing table as it happens in case of some physical link goes down and IGPs like OSPF or EIGRP recalculates the routes. As the old routes do not vanishes hence our router do not recalculates the new routes and traffic keeps taking the at&t path and getting lost in their AS. Every time such problem occurs we need to bring the back up iplc in BGP manually and only after that India-US traffic takes the IPLC path due to shortest AS distance. We want to avoid this manual configuration and want something automated. Please suggest the best strategy to achieve that in such scenario.

Is there any possibility routing decision can be made based upon ping or trace result??

Let me know if network diagram is needed for scenario.

  • LAN Switching and Routing
1 REPLY

Re: Routing issue in MPLS VPN

Hello,

the best bet would be "object tracking". This feature allows to trigger rerouting based on an "object". An object can be defined to be f.e. reachability to a server through ping. Basically you can instruct a router to ping an IP with a configurable frequency. If f.e. 3 consecutive pings are failing then rerouting through a backup can be triggered.

In fact there are much more options to define an object. A sample configuration would look like this:

ip sla monitor 1

type echo protocol ipIcmpEcho 10.1.1.1

timeout 2000

frequency 5

threshold 3

request-data-size 1490

ip sla monitor schedule 1 start-time now life forever

!

The full picture is given f.e. in "Reliable Static Routing Backup Using Object Tracking"

http://www.cisco.com/en/US/products/sw/iosswrel/ps5413/products_feature_guide09186a00801d862d.html

Hope this helps! Please use the rating system.

Regards, Martin

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