OSPF Query

[subashmbi]

Hi All,

Please find the topology diagram for reference.

1) We have 2 Locations :- Site-A(Primary) & Site-B(DR).

2) Site-A(Primary) & Site-B(DR) is already interconnected.

3) Branch offices are accessing the application from Site-A, Because the server is located in Site-A.

4) Site-A is connected to the customer router using static routes and already static route is redistributed into the OSPF.

5) Site-B is also connected to the customer router using static routes but this routes are not injected into the OSFP

Req:-(a) The site-A is down , I want to Automatically switch over to Site-B. Kindly advice what are the  changes in my OSPF configuration .

B) Once site-A is comming up, again automatically fall back to primary site.

Regards,

Suba

[Richard Burts]

Suba

It seems to me that if you want to fail over automatically and to fail back automatically the first thing that you need to do is to have both OSPF redistribute their static routes. In doing the redistribution you can manipulate the metric (or perhaps the external type) so that the routes from site A are preferred if they are present and routes from site B will be used when there are problems with site A.

The second thing that you need to do is to have a mechanism that can determine when site A is working correctly, can detect a failure, and can withdraw the static route at site A. There is a feature of Object Tracking that can monitor reachability from site A to the remote and when there is a problem can withdraw the static route at site A. When implemented this feature will allow you to automatically fail over and to fail back.

HTH

Rick

[subashmbi]

Hi Richard,

Thanks for the update.

First Step: I will do static routes redistributes into the OSPF both the sites.

Please find the below current config for site-A and Site-B

I have one clarification, Because current conifg  all the static routes are redistributed into the ospf with default metric.So I want to exclude my customer route (1.1.1.x) and given the metric.Kindly advice me how can i achieve this scenario.

For site-B , the current config my customer routes are not redistributed and this alco i want to exclude my customer routes

Please share me the metric config for this scenarion based on the below scenario:-

Site:A

----------

router ospf 75
router-id X.X.X.X
log-adjacency-changes
redistribute connected metric-type 1 subnets route-map connected-to-ospf
redistribute static metric-type 1 subnets route-map static-to-ospf
redistribute bgp 11086 metric-type 1 subnets route-map BGP-to-OSPF-Routes
network X.X.X.0 0.0.0.255 area 0.0.0.0

!

!
ip access-list standard static-advs
deny   X.X.X.0 0.0.0.255
permit any
!
route-map static-to-ospf permit 10
match ip address static-advs
!
ip route X.X.X.X 255.255.255.255 192.168.75.10

Site-B

---------

router ospf 117
router-id X.X.X.X
log-adjacency-changes
redistribute connected subnets route-map connected-to-ospf
redistribute static metric-type 1 subnets route-map static-to-ospf
redistribute bgp 11086 metric-type 1 subnets route-map BGP-to-OSPF-Routes
network X.X.X.X.0 0.0.0.15 area 0.0.0.0
distribute-list default-from-ospf in BVI117
!
ip access-list standard static-advs
permit X.X.X.X

!
!
route-map static-to-ospf permit 10
match ip address static-advs
!
ip route x.x.x.x 255.255.255.255 192.168.117.2

For second option u had mentioned some tracking option. iF u have any template please share this also

[subashmbi]

Kindly update ASAP

[Richard Burts]

Suba

Here is a brief example of using tracking for a static route. If the tracked object is reachable the static route is put into the routing table and if the tracked object is not reachable the static route is withdrawn.  In this example the tracked object is the next hop but could be some other address that would indicate whether the static route would effectively forward traffic and the traffic would reach the next hop. One time I implemented this for a customer where the next hop was their DSL modem. We decided to track an object further into the provider network because it gave us a better indication whether the static route was really getting traffic to where it should go.

!

ip sla monitor 1
type echo protocol ipIcmpEcho 10.1.1.242
timeout 1000
frequency 3
threshold 2
!
ip sla monitor schedule 1 life forever start-time now
track 123 rtr 1 reachability
!
ip route 0.0.0.0 0.0.0.0 10.1.1.242 track 123
!

for more detail you could use this link:

http://www.cisco.com/en/US/partner/docs/ios/dial/configuration/guide/dia_rel_stc_rtg_bckup_ps10591_TSD_Products_Configuration_Guide_Chapter.html#wp1065558

HTH

Rick