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In the image below i run quagga ospfd daemons as routers in picture. I want to add 1+1 redundancy to 172.16.1.0 network this way: if 172.16.1.1 became unavailable 172.16.1.128 changes its IP address to 172.16.1.1 assigns relevant IP addresses to its interfaces and replace the now unavailable router. This process requires ospf to learn topology and converge in the new board and make network disconnected for some while. So i need a way to sync ospfd on 172.16.1.1 with ospfd on 172.16.1.128. network

  • I don't get it, the whole purpose of routing protocol like OSPF is to have all routers participating in it, so a switchover can happen quickly. If you want a board to be "primary" and the other "secondary" you can adjust OSPF costs. – JFL Jun 21 '17 at 7:54
  • the redundant board must change its IP in case of a switchover and i think we need restarting ospfd daemon and then learned state vanishes. @JFL – mhk Jun 21 '17 at 8:12
  • In other words (1) i want the redundant board to listen for hello messages and learns topology but as it is in the same subnet as working board do not advertise itself as a router. (2) i want to change board ip and replace it with previously working board in event of a failure and i need routing state to be persistant (to reduce convergence time) – mhk Jun 21 '17 at 8:25
  • i need redundant routers not routes. – mhk Jun 21 '17 at 8:35
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    This seems a weird design. What your are trying to do may not be the best solution to your problem . If you can describe (not in comment but by editing your question) what you are actually trying to achieve we may come with better solution. See What is the XY problem? – JFL Jun 21 '17 at 8:35
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There's really no need to change the IP address of the device, as long as your devices support VRRP (since it is linux based, it does)

Give to both devices an address within 172.16.1.0/24 (like .2 and .3) and set 172.16.1.1 as a virtual address with VRRP

Then configure OSPF on all devices, setting the cost so the primary router will be preferred over the backup one.

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