As if I didn’t have enough to do, I got handed another great management "what if” scenario…
“What if there was a fire or a flood that affected the network core or a specific distribution layer?”
On a large campus with several buildings, I am looking at separating several chassis between two buildings. That got me wondering about how far I could separate any paired chassis without causing an issue. All of the chassis connect at 10GE and all of the fiber is single mode. Since it is a campus, I am not worried about exceeding the distance limitations of 10GE over single mode fiber. The X2-10GB-LR and SFP-10G-LR have a maximum cable distance of 10km. Without an OTDR it is hard to guess the actual distance, but I would estimate less than 1000 meters hopefully. I would get the fiber measured before I actually went down this path.
The first chassis pair would be a 6500s running as a typical VSS cluster. Are there any issues with the Virtual switch link (VSL) or the Bidirectional Forwarding Detection (BFD) link going 1000 meters? All I could find on distances was a note that said: “Maximum VSL distance depends on X2 optics used for VSL 10 Gigabit Ethernet connections.” The majority of connections to the VSS cluster are L3 links from various building distribution layer switches. I do not see an issue as these are all independent L3 links not ehter-channels. But there are also a few L2 Access Layer switches that are dual connected (MEC) to the VSS cluster, would there be any issues (timing or otherwise) on the ether-channel? Obviously one leg in the channel-group would be a greater distance than the other leg.
The second chassis pair would be newer Nexus 7000s. These have the vPC peer-links and the vPC peer-keepalive links between them and have several L2 only Nexus 5500 pairs redundantly attached to them using Virtual Port Channels (vPC). I haven’t been able to find anything that states a distance limitation to the vPC peer-links or peer-keepalive links or for things connected via a vPC. Here again the Nexus 5500s would have some of the ports in the vPC that were a lot longer than others.
Since the Nexus 5500s are all in the primary datacenter building, I probably wouldn’t split them up between buildings. I would prefer just to split the Nexus 7000s and install additional 5500s in the second building to support redundant servers located there.
Just wondering if I am missing something here on the distances that would cause issues down the road.
Anyone ever done this? Pros & Cons?
