Forum Discussion
Abhzi_114202
Nimbostratus
NimbostratusIP Conflict in Server and F5 load Balancer
We faced an issue where server became inaccessible after reboot. It was not in network. While viewing from console we came to know that it was unable to assign IP address to the server and was throwing error " some other device is already using IP address".
Later we realized that IP was configured same in F5 load balancer and because of this we were facing issue. Once we took off the IP from F5, server was able to boot with that IP address. But now F5 is not getting configured. I don't have much knowledge on F5, but wondering if someone has faced similar type of issue.
Please advise.
5 Replies
- Kevin_Stewart
Employee
Can I assume you're trying to use the same IP address on the F5 that you're using for the Linux server? And are you configuring the F5 to load balance services on the Linux server? If yes to the first, it's generally not meant to work that way when load balancing end point services like web servers. In this case the F5 presents a virtual representation of an application to users with a single dedicated IP address. Users contact that IP address for services and the F5 load balances those requests to potentially many servers on different IP addresses. The F5 would not use the same IP address assigned to another server. 
Abhzi_114202Thanks Kevin for replying!! I think I have now some knowledge about F5 working.
The case I am referring, here F5 is actually acting as an gateway only. This Linux server does not have any other server in relation to balance load. So, even in this scenario we can not keep the ip on linux server and F5 same?- Kevin_StewartFrom a routing perspective, it's generally not acceptable (unless doing something like Anycast) to use the same IP address on multiple devices (in the same subnet). You can get away with it though, as Aaron mentioned in a previous post, by statically defining the ARP entries on the client devices, but that's probably not your intention either. Can you elaborate on your gateway configuration? And also why you need to have the same IP on both of these devices?
- Abhzi_114202I apologize for my less knowledge on F5. But if suppose I have to give same ip then what will be the static ARP entries that to be done at client end? Our gateway is 10.107.15.1 and my linux server 10.107.15.111. My F5 has ip 10.107.15.12.
And secondly if I give different ip at F5 then how will it be linking with my physical server ip? There is altogether different team working on F5, so I willadvise them what you'll suggest. Please. - Kevin_StewartYou listed a bunch of different IP addresses. Can you elaborate on WHERE and WHY you have duplicated an IP address between the Linux server and the F5? Can you also elaborate on what you're trying to accomplish?
