Patrick <centos at puzzled.xs4all.nl> wrote: > I am trying to come up with an architecture that has some > redundancy. The idea is to hook up the two GbE LAN > interfaces of a CentOS server to two Gigabit Ethernet > switches. In case one switch goes down, there is a > redundant path (the server is redundant too). > How would I acomplish this? First off, doing it at the layer-3/IP level with dynamic routes is far more overhead than is required. In your case, you're just looking for layer-2/802 level. So leverage what standard 802 offers if you can. I'm more of an academic, so the first thing I recommend to people is that they get familar with the standard capabilities of 802. More explicitly, research 802.1d Spanning Tree Protocol (STP) as well as newer standards like 802.3ad Link Aggregation. In fact, it's this latter addition that really makes things very easy. In the "good old days," you'd setup a single, virtual UNIX interface bridged to two. Your system only knows about the single, virtual UNIX interface. But it would then leverage two interfaces, only bringing the other interface up if one failed. With support for STP, loops would be avoided. The only thing to worry about with STP is the maximum number of hops in a layer-2 network -- 7. This, of course, requires both your host (software) and network stack (firmware) to support STP. In the "new, better days" we now have 802.3ad Link Aggregation. Now you can get more bandwidth and failover at the same time. Again, both your host (NIC firmware) and network stack (firmware) need to support 802.3ad Link Aggregation. But if it does, it becomes very, very easy to configure a single IP address to a pair of NICs, and aggregate both to two different ports in a network stack. Now if you're using cheap network equipment, I don't know what to tell you. Layer-2 is probably out then. > Can I use IP addresses from one IP network (say 10.0.0.0/24) > to assign to the 2 LAN ports on the CentOS server and a port > on each of the GbE switches and then use something like OSPF > on the switches and the CentOS box to do the routing? You can maybe use layer-3 hacks and tweaks to deal with things, but it's very difficult to handle the failover without support at the concentrator end. Your idea to use different IP addresses and dynamic routing tables is probably the best way. But it's definitely not as clean. Especially with 802.3ad Link Aggregation being supported more and more. > Any other ideas? If you let me know what your networking equipment and/or budgetary constraints are, I can help you further. You'd be surprised how little this actually costs, but if you're using $200 GbE switches, then I can't help you with layer-2. -- Bryan J. Smith | Sent from Yahoo Mail mailto:b.j.smith at ieee.org | (please excuse any http://thebs413.blogspot.com/ | missing headers)