Addendum
exists between the ToR and leaf switch units, and between the leaf and spine units or nodes. For example,
you can enable the optimized booting method in a deployment in which Micrsoft Bing and Microsoft
Azure applications are installed, although different QoS configurations might be needed because of Bing
being a search utility and Azure being a service provider that hosts a public cloud.
Consider a sample scenario in which to the south or lower end of the ToR switch, which is an S6000
Switch, the storage servers are connected. To the north or the upper end of the ToR switch, leaf nodes
are connected. Spine nodes are at the top of the vertical hierarchical configuration and are connected to
the leaf nodes. You can connect up to 96 physical servers in 4 to 5 different subnets, and up to 8
Multiprocotol BGP (MP-BGP) sessions to the servers, that function as load balancers. All the servers are
single-homed servers, which does not provide redundancy to servers if a ToR switch fails. The servers
advertise both IPv4 and IPv6 addresses. Layer 2 network is to the south of ToR and Layer 3 network is to
the north of ToR. An EBGP hold timer of 10 seconds and BGP graceful restart are specified. A maximum
of 4000 routes each for Ipv4 and IPv6 traffic can be supported.
To the north of the ToR switch, up to 8 leaf nodes are connected. Different EBGP sessions for IPv4 and
IPv6 for each leaf node are configured. LACP is enabled between the ToR and leaf nodes, and the LACP
long timer is set to the default value. You can enable the optimized boot functionality in such a topology.
Booting Process When Optimized Boot Time Mechanism is Enabled
When a S6000 switch running Dell Networking OS earlier than Release 9.3.0.0 is reloaded, the CPU and
other components on the board are reset at the same time. Therefore, the control plane and the
forwarding plane are impacted immediately. After the system boots up and reinitializes, the interfaces
come up, control plane protocols are reestablished, network topology information (such as routes,
adjacency settings) is learned and installed before the traffic resumes. It is observed that in a typical
network scenario, a traffic disconnection of 150 seconds or more occurs. When you employ the
optimized booting functionality, the traffic outage duration is reduced in a sizeable way.
Guidelines for Configuring Optimized Booting Mechanism
Keep the following points and limitations in mind when you configure the capability to minimize the
booting time:
• The Fastboot functionality is supported only when you perform an expected, stipulated reload by
using the reload-type normal-reload command in Global Configuration mode or by using the reset
command in uBoot mode on a switch that is running Dell Networking OS Release 9.3.0 or when you
perform a planned upgrade (and not an abrupt or unexpected shutdown) from an older release of Dell
Networking OS to Release 9.3.0.0 or later, which supports the fast boot capability. We recommend
that you do not perform a downgrade of your system from Release 9.3.0.0 to an earlier release that
does not support the fast boot functionality. If you downgrade the system to a release earlier than
Release 9.3.0.0, the system behavior is unexpected and undefined.
• The Fastboot functionality uses the Symmetric Multiprocessing (SMP) utility that is enabled on the
Intel CPU on the S6000 Switch to enhance the speed of the system startup. SMP is supported on the
S6000 platform.
For the fastboot mechanism to reduce the traffic disruption significantly, the following conditions apply:
1. When LACP is used between the ToR switch and the adjacent devices, LACP is configured on these
adjacent devices with a timeout value of 90 seconds or longer.
2. BGP timers between the ToR switch and adjacent devices are set to high values (for example, a hold
timeout of 180 seconds) unless BGP graceful Restart is used.
Flex Hash and Optimized Boot-Up
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