Ok, lets try again. It seems Im having problem asking the right questions so lets take it from the beginning. I work at a HPC center at a university. We have a number of small (<300 nodes) clusters and a few storage systems. To our site we get a statically routed /22 network.
Today we have the whole /22 in a single broadcast domain and we have decided to redesign and renumber the network for better scalability and performance. To do this we have bought two new L3 switches (Dell s6000-on) to use as our backbone. Connected to these we will have the aggregation switches of the individual clusters (which are HP 5400) and it will look something like this:
Now we want to renumber the hosts with private IP-adresses (one net per cluster) and use OSPF internally, to reach the internet we still use a default route to some central university router.
One important thing is that we still need to have some hosts with public IPs reachable from the internet (a few login nodes per cluster and some other services).
My first question has to do with the links between Core and aggregation. I could use MC-LAG (Dell VLT), Stacking or just OSPF everywhere.
- With MC-LAG I can have all links on the same vlan and its very easy to have other vlans span the whole network
- But it feels to me that ptp-links and OSPF eclb is more robust and scalable.
- Or I can use switch stacking which gives me a virtual chassi and get rid of the need for MC-LAG. But I don't really trust the stability of such a technique.
The machines on private IP-adresses still need internet, so I want to NAT them out. But our new core switches doesn't support NAT (as far as I know) so we are setting up a NAT-router on the side. Is there some smart way in OSPF to redirect traffic from privates IPs to the nat-router? Or should I use PBR?
Do you have any solution for the public IPs? They are sort of scattered throughout the datacenter so there is not a single access point for these machines. It would be very helpful to have a large vlan with a /24 or so that spanned the whole network, see question 1. But maybe the best way is to just split up the network into smaller ones and route them with OSPF as needed.
Some of you say its a bad idea to have both public and private IPs in the same OSPF area. If this is so, what do you think we should do instead?
I hope this makes it more clear what Im after. Please feel free to ask for clarifications