OSPF High Available Design

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Jul 15th, 2012
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I am trying to setup a redundant , High available OSPF network. Pls see attached.

The switches are also running OSPF instances with Routers, on both Primary and Seconday path. Do i need to setup OSPF peering between switches also (over the trunk) so each switch will have both different costs routes, in case 10 is not available it will install 100 in the routing table.

Or any other idea/suggestion will be helpful in desing a full redundant network.


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Reza Sharifi Tue, 07/17/2012 - 18:23
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Is the host in vlan 80 connected to two different switches? Are both NICs on the same subnet?

If yes to both than you need a trunk between the 2 lower switches for VRRP/HSRP. Then for OSPF redundancy, you need cross connects between the lower switches and the routers in the middle.


Marwan ALshawi Tue, 07/17/2012 - 22:35
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from your topology

looks like the end host multi-homed to both switches and your are using HSRP for gateway service

if you want to use OSPF with optimal path selection you need to add a link from each router to the other switch and make a fully meshed topology where each router to be connected to both switch using L3 links

then change the ospf cost to make the path to the primary router from both switch prefered with lower ospf cost

since you are using HSRP no need to form ospf over the inter switch link/trunk hsrp will take care of which switch to be the gateway

hope this help

mzeeshan321 Tue, 07/17/2012 - 22:51
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Marwan - While i am short of ports on the routers, it looks difficult to create a L3 with the other switch.It was a good idea, though.

In case of interswitch OSPF, yes HSRP will take care  of only the server facing vlans, but how if the Switch uplink  (conencting to router) goes down or the uplink router it-self goes down.  In this case Primary switch will be getting the routes over the  inter-switch OSPF (with a higher cost) and flows the traffic through  seconday link.


patelvc7601 Thu, 07/26/2012 - 13:00
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I see your point, Munawar. I think you should use OSPF b/w switches Unless your plan is to use Advance HSRP Tracking

for any upstream failure ( direct or indirect). My vote is for run OSPF b/w switches.

You can lab it up with GNS3. You do not need all the fancy config you are just testing the routing functionality.




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