OSPF - Redundancy Two Links

[netbeginner]

Dear All,

We have two sites with two routers each.  Both these sites are connecting with Two point-to-point links. All running with Static routes.

For Eg:-

Site A:- 

Router-1 Link WAN IP:- 10.0.0.1

Router-2 Link WAN IP :- 20.0.0.1

LAN HSRP VIP :- 10.40.0.1/27

LAN Pool :- 172.16.0.0/24, 172.16.2.0/24, 172.16.4.0/24, 172.16.6.0/24

Site B:- 

Router-1 Link WAN IP:- 10.0.0.2

Router-2 Link WAN IP :- 20.0.0.2

LAN HSRP VIP :- 10.80.0.1/27

LAN Pool : 192.168.0.0/24, 192.168.2.0/24, 192.168.4.0/24, 192.168.6.0/24

There are multiple pools running on LAN at each end.

We would like to run OSPF between these routers, such that Link-1 will be Primary and Link-2 will be standby.  I know we have to set the cost on interface and lowest will be preferred along with redistribution (for static routes) at each end but still like to take expert advise. Pl note that these two locations having distance of approx. 100 Km and service providers transmission media also involved in between.

Diagram attached for reference.

Pl suggest.

Rgds

***

[Borgenstrand]

Hi.
You have HSRP on, if that is true, then the HSRP Active router will have the best path to the other office if the WAN link have the same speed.
Is the speed the same on the two WAN links?

[Richard Burts]

It really does not matter much whether the links have the same speed or not if the interface bandwidth is modified or if the interface ospf cost is manipulated. If the ospf metrics are not the same then there will be a primary link and a backup link, no matter whether the physical speed is the same or is different.

You do make an interesting point about HSRP. It would be desirable to configure the HSRP so that the router connected to the primary link was the HSRP active router.

To the original poster

You have not provided much detail about how these routers are configured so we can only make assumptions about the environment. But one thing that I would be concerned about is your reference to redistributing static routes. You certainly can redistribute static and if you do this then the router will advertise to its neighbors these routes. But on the originating router it still is a static route. So if the router connected to the backup link has a static route for the pools at the other site and if that router receives a packet with destination address in that remote pool then the router will forward the packet using its static route and not use the OSPF learned route.

HTH

Rick

[netbeginner]

Dear Richard & Borgenstrand   ,

HSRP is configured toward LAN side, this is fine that Active Router (HSRP) will take the path forward but for LAN traffic.

My query here is, let us assume...If Link-1 (Router-1 end or at Router-2 end) fails ..even in that case Router-1/2 will be active due to HSRP (at LAN end) and downstream device will continue to forward traffic toward Router-1 and post then same will be forwarded to link-1 which is actually down.

To avoid this situation..we can have option of IP SLA to track remote(WAN IP) and if goes fail(not reachable) then traffic should be auto fallback to secondary link (link-2)

But , we would like to go with OSPF and hence raised query on OSPF implementation. If someone is having CLI or documentation..pl share.

Rgds

***

[Richard Burts]

It would be possible to get this to work with HSRP and static routes. But I believe that implementing OSPF and removing the static routes will be a better solution. You still have not given us much information about how your network is set up. The drawing shows a switch connected to the LANs and then connecting to the routers. The drawing suggests that the connection between the switch and the routers is a routed link but is not clear about this. Can you clarify the relationship between the switch and the routers. Is the switch a layer 3 switch and does it route from the LANs to the routers? If so then the switch should participate in OSPF and it would be a very clean and simple solution. And it would not need HSRP.

You could have the switch advertise its connected LAN subnets to both routers. The routers would advertise the LAN subnets to the remote routers and with manipulation of the OSPF cost you could establish a primary link and a backup link. If there were a problem on the primary link then OSPF would recognize the loss of connectivity and would automatically switch over to the backup link.

HTH

Rick

[netbeginner]

Hello,

Any more suggestion for OSPF...