Given :
- 2 Datacenters + 1 Users Site.
- Every site has a Layer 3 switch as a core.
Task :
To interconnect the 3 sites in a triangle as in the picture attached
The interconnection between Datacenter1 and Datacenter2 has to be a L2 extension in order to have High Availability Clusters on 2 sites
Solution:
I decided to inteconnect the sites as follows:
- DC1 (Datacenter1) - DC2 : L2 Trunk link
- DC1 - Users site : L3
- DC2 - Users site : L3
OSPF between the 3 cores
DC1 - Users Site is the OSPF prefered link
For the extended VLANs (Between DC1 and DC2) there will be HSRP implemented on DC1 and DC2 core switches.
PROBLEM :
The problem comes when the trunk link between DC1 and DC2 Core switches goes down:
Suppose that in HSRP - DC1 Core is Active and DC2 Core is Passive.
1. When the trunk link goes down, HSRP of DC1 thinks that DC2 went down - so it stays Active. But DC2 HSRP thinks that DC1 is down, so it changes the state from Backup to ACTIVE. So now we have 2 IP addresses of 192.168.10.1 on the network.
2. The servers (.10 and .11) will also loose the interconnection. So they will also both be active.
This is a big problem.
Question :
How can we solve this issue ? Is there a way to make few changes in the design in order to assure that VRRP and HSRP continue to work correctly if the trunk link goes down ? (Duplication of trunk link is not an option)
Thanks in advance. Any answer is highly appreciated.
