Load Balancing And Route Backup; Route Recursion; Sharing Of Routing Information - 3Com MSR 50 Series Configuration Manual

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Load Balancing and
Route Backup
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Route Recursion

Sharing of Routing
Information
Routing approach
EBGP
UNKNOWN
The smaller the priority value, the higher the priority.
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The priority for a direct route is always 0, which you cannot change. Any other
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type of routes can have their priorities manually configured. 256 represents a
route from an untrustworthy source.
Each static route can be configured with a different priority.
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IPv4 and IPv6 routes have their own respective routing tables.
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Load Balancing
In multi-route mode, a routing protocol can be configured with multiple
equal-cost routes to the same destination. These routes have the same priority and
will all be used to accomplish load balancing if there is no route with a higher
priority available.
A given routing protocol may find several routes with the same metric to the same
destination, and if this protocol has the highest priority among all the active
protocols, these routes will be considered valid routes for load balancing.
In current implementations, routing protocols supporting load balancing are static
routing, RIP, OSPF, BGP and IS-IS.
In current implementations, routing protocols supporting load balancing are static
routing, RIP, OSPF, BGP, and IS-IS.
Route backup
Route backup can help improve network reliability. With route backup, you can
configure multiple routes to the same destination, expecting the one with the
highest priority to be the main route and all the rest backup routes.
Under normal circumstances, packets are forwarded through the main route.
When the main route goes down, the route with the highest priority among the
backup routes is selected to forward packets. When the main route recovers, the
route selection process is performed again and the main route is selected again to
forward packets.
The nexthops of some BGP routes (except EBGP routes), static routes configured
with nexthops, and multi-hop RIP routes may not be directly connected. To
forward the packets, the outgoing interface to reach the nexthop must be
available. Route recursion is used to find the directly connected outgoing interface
based on the nexthop information of the route. Link-state routing protocols, such
as OSPF and IS-IS, do not need route recursion because they obtain nexthop
information through route calculation.
As different routing protocols use different algorithms to calculate routes, they
may find different routes. In a large network with multiple routing protocols, it is
required for routing protocols to share their routing information. Each routing
Routing Protocol Overview
Priority
255
256
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