Dell ECS EX Series, Hardware Manual

Page: 74 / 112

Figure 62. Ring topology
The ring topology is very similar to the daisy chain/line topology, except that it is more robust since it requires two points of
failure to break the topology which would cause a split-brain issue.
The inter-rack ring topology between EX-Series racks are shown in the following figure.
Figure 63. Inter-rack switch connectivity - ring topology
Star topology
The limitation with the daisy chain or ring topologies is that they do not scale well for large installations. For ten or more ECS
racks, one or two aggregation switches should be added support the large installation. For high availability, the recommended
topology is to use two aggregation switches with port channel (VLT, vPC, MLAG) connectivity between them. If you use a
single aggregation switch, both the Fox switch (BE1) and the Hound switch (BE2) are connected to the single switch. The
impact of using only one aggregation switch is the loss of high availability for the aggregation switch. For connectivity to
aggregation switches, use the inbound port 41 on each back-end switch to link to the aggregation switch(es).
By using aggregation switch(es) to connect to all the intra-rack networks, the star topology provides better protection against
the split-brain issue than both the daisy chain/linear or ring topologies. With aggregation switch(es), link failures are isolated to
a single intra-rack network in the private.4 network.
74 EX300 Platform