Dell Networking S6000 Uživatelský manuál stáhnout pdf (Strana 336)

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dynamic ARP or ND database entries are not present or required to be restored. The system boot up

mode will not be fast boot and actions specific to this mode will not be performed.

Software Upgrade

When fast boot is used to upgrade the system to a release that supports fast boot, the system enables the

restoration of dynamic ARP or ND databases that were maintained in the older release from when you

performed the upgrade and the ARP and ND applications identify that the system has been booted using

fast boot.

LACP Fast Switchover

For fast boot, the operation of LACP has been optimized. These LACP optimizations are applicable even

when fast boot is not enabled when a system reload is performed. These enhancements are controlled

using the fast-switchover option that is available with the lacp command in Port Channel Interface

Configuration mode. When LACP ‘fast-switchover’ is enabled on the system, two optimizations are

performed to the LACP behavior:

• The wait-while timer is not started in the ‘waiting’ state of the MUX state machine. The port moves

directly to the ‘attached’ state.

• The local system moves to the ‘collecting’ and ‘distributing’ states on the port in a single step without

waiting for the partner to set the ‘collecting’ bit.

Changes to BGP Multipath

When the system becomes active after a fast-boot restart, a change has been made to the BGP multipath

and ECMP behavior. The system delays the computation and installation of additional paths to a

destination into the BGP routing information base (RIB) and forwarding table for a certain period of time.

Additional paths, if any, are automatically computed and installed without the need for any manual

intervention in any of the following conditions:

• After 30 seconds of the system returning online after a restart

• After all established peers have synchronized with the restarting system

• A combination of the previous two conditions

One possible impact of this behavior change is that if the amount of traffic to a destination is higher than

the volume of traffic that can be carried over one path, a portion of that traffic might be dropped for a

short duration (30-60 seconds) after the system comes up.

Delayed Installation of ECMP Routes Into BGP

The current FIB component of Dell Networking OS has some inherent inefficiencies when handling a

large number of ECMP routes (i.e., routes with multiple equal-cost next hops). To circumvent this for the

configuration of fast boot, changes are made in BGP to delay the installation of ECMP routes. This is done

only if the system comes up through a fast boot reload. The BGP route selection algorithm only selects

one best path to each destination and delays installation of additional ECMP paths until a minimum of 30

seconds has elapsed from the time the first BGP peer is established. Once this time has elapsed, all routes

in the BGP RIB are processed for additional paths.

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Flex Hash and Optimized Boot-Up

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