Advertise Routes when destination unreachable

[ahmad82pkn]

Guys, need your help again as always.

What i want to achieve is track a destination, if that destination is unreacable then bring that static route into routing table.

i know Track can take our route from routing table if destination is unreachable, i want to bring route into table if destination is unreachable.

actually my Site A is advertising some routes in my internal MPLS cloud. if Site A WAN link goes down.i want to advertise same routes from Site B router. so i want to track Site A wan link or loopback from Site B router and advertise same routes if Loopback of Site A not reachable.

any suggestion?

[rais]

Does it mean that constantly advertising routes from site B with inferior metrics [when compared to those of site A] won't work for you?

Thanks.

[ahmad82pkn]

in my design not an option, i am running OSPF with carrier PE router, and they are doing BGP internal in their MPLS core. and all my attributes are lost in their cloud.

Regards,

[rais]

Try this out.

There is also a conditional default-route advertisement supported on Cisco ospf that you might be able to use.

HTH.

[ahmad82pkn]

thank you, i will try this and see if it serves the purpose. thank you Rais.

[Nandan Mathure]

@ahmad82pkn

You can create a tracked object. Then create a event manager applet for "event track , state = down" and insert required "action cli " for advertising routes. & another applet to reverse the action when state = up.

That should work.

Nandan Mathure

[ahmad82pkn]

can you give me some document URL for this?

[Nandan Mathure · Accepted solution]

Hi!

As per what you stated "  What i want to achieve is track a destination, if that destination is  unreacable then bring that static route into routing table"

I couldt find a related example on cisco website which fits, but i have a config for you which i wrote.

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track 1 ip route 10.10.10.10/24 reachability

  event manager applet TRACK_IF_DOWN

    event track 1 state down

    action 1.0 cli command "enable"

    action 2.0 cli command "conf t"

    action 3.0 cli command "ip route 192.168.1.0 255.255.255.0 192.168.2.1"

    exit

  event manager applet TRACK_IF_UP

  event track 1 state up

  action 1.0 cli command "enable"

    action 2.0 cli command "conf t"

    action 3.0 cli command "no ip route 192.168.1.0 255.255.255.0 192.168.2.1"

  exit

------------------------------------------------------------------------------------------------------------------------------

1] You can change the commands as per your need like for vrf "ip route vrf " and so on.

    Here is the link for Emebeded Event Manager

    http://www.cisco.com/en/US/docs/ios-xml/ios/eem/configuration/12-4t/eem-12-4t-book.html

2] You can use IP SLA with TRACK for tracking the destination as well.

Let me know if this helped. Thanks.

[ahmad82pkn]

that is something really cool never came to know such flexibility exists .

Looks like my life is going to be lot easier.

thank you very much Nandan

[Vasileios Bouloukos MSc, ITIL, CCIE]

Hi,

If you can not modify the attritbutes to the MPLS network and you run ospf  between PE-CE I would recommend an other solution.

From the site A which is the primary site you could advertise all your subnets to the MPLS.

From the site B which is the backup site to advertise an ospf summary address  of these subnets.

So, the MPLS network, when both A and B are up selects the most specific subnets of Routers A to route the traffic. If Router A fails the traffic is routed via the summary address of Router B.

Hope that helps,

Vasilis

[ahmad82pkn]

hi Vasileios, Thats what i am doing right now i thought to find another way.