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Graceful restart for dynamic routing protocols
Along with VCStack, the other key component of this IPv6 high
availability solution is the implementation of graceful restart
(also known as non-stop forwarding) within IPv6 dynamic
routing protocols. Graceful restart is a feature that has been
added to routing protocols (RIP, OSPF, BGP) in recent years. It
enables Layer 3 routing to continue uninterrupted even while
one of the routers in the network is, for a brief period, not
participating in the routing protocol that is used to populate the
routers’ route tables.
In normal circumstances, when routers detect that a neighbor
is no longer participating in the routing protocol, they discard
routes learnt from that neighbor. With graceful restart, the
router that is going to briey drop out of the protocol can
inform its neighbors of its intention, and request that they
continue to operate as though it was still participating.
Combining VCStack and graceful restart allows achievement of
true Layer 3 router resiliency. VCStack enables multiple Layer 3
switches to operate together as one, and graceful restart keeps
data owing if the master switch of the VCStack is lost and the
stack briey drops out of a routing protocol while a new master
takes over.
Combining that with graceful restart within the routing
protocols provides a solution that can enable a Layer 3 switched
IPv6 network to hitlessly recover from link loss, and recover
from the loss of a stack member in very few seconds.
Summary
The standard Internet protocol of the future is IPv6. In the
coming years, a great deal of time and effort will be expended
in the process of transferring data communication systems
from IPv4 to IPv6. The simpler this process is made for
people, the more smoothly it will progress, and the less it will
cost.
By providing a resilient Layer 3 switching solution, at an
affordable price, that enables IPv4 and IPv6 to work in parallel
with equal reliability and performance, Allied Telesis is able to
help smooth the transition, as shown in diagram 3.
Full support for IPv6 transition technologies and resilient
network products and protocols ensure that Allied Telesis
switching technology provides a solution that is easy to
manage, scalable and future-proof.
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IPv4 and IPv6 dynamic routing in parallel
via a VCStack L3 Switch
Diagram 3 - IPv4 and
IPv6 dynamic routing in
parallel via a VCStack
Layer 3 switch
High Availability IPv6 |7