Configuring Load Sharing - HP 7102dl - ProCurve Secure Router Configuration Manual

IP Routing—Configuring RIP, OSPF, BGP, and PBR

Configuring Load Sharing

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Configuring Load Sharing
Load sharing allows the router to select up to six best routes to a destination.
Load sharing is important when your router connects to a remote site (or to
the Internet) through connections to multiple remote routers.
Because best routes can be discovered using any method, you can use load
sharing with any dynamic routing protocol or with static routing. (See Chapter
11: IP Routing—Configuring Static Routes in the Basic Management and
Configuration Guide for more information on configuring load sharing with
static routes.) However, every best route must still have the lowest metric and
administrative distance to be selected. That is, if your router has two connec-
tions to a remote site, you cannot configure RIP on one connection and a static
route that uses the other connection and expect the router to use both
connections. The static route will have a lower administrative distance than
the RIP route, so even when load sharing is enabled, the router will only select
the static route.
You enable load sharing with this command, entered from the global configu-
ration mode context:
Syntax: ip load-sharing [per-destination | per-packet]
You can configure the router to balance traffic:
per destination
per packet
ProCurve Networking generally recommends that you select the per-desti-
nation option. When the router balances traffic per destination, it assigns
packets to routes based on the packets' source and destination addresses.
That is, when the router must forward a packet to a destination for which
multiple routes exist, it hashes the packet's source and destination address
and, according to this value, assigns the packet to a route. (The router
performs the hash function so that a source and destination can only resolve
to as many different values as routes are available in the routing table.)
Therefore, per-destination load sharing does not balance traffic exactly
equally; two successive packets may be sent over the same route, even if they
have different source and destination addresses. Packets in the same session
always take the same route because they have the same source and destination
address. The more traffic that the router supports, the more evenly it will
balance the traffic.