Quick Reference Guide

PowerConnect B-Series TI24X Configuration Guide 597
53-1002269-02
Configuring IP parameters – Layer 3 Switches
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• The route path, which can be one of the following:
• The IP address of a next-hop gateway
• An Ethernet port
• A virtual interface (a routing interface used by VLANs for routing Layer 3 protocol traffic
among one another)
• A “null” interface. The Layer 3 Switch drops traffic forwarded to the null interface.
You also can specify the following optional parameters:
• The metric for the route – The value the Layer 3 Switch uses when comparing this route to
other routes in the IP route table to the same destination. The metric applies only to routes
that the Layer 3 Switch has already placed in the IP route table. The default metric for static IP
routes is 1.
• The administrative distance for the route – The value that the Layer 3 Switch uses to compare
this route with routes from other route sources to the same destination before placing a route
in the IP route table. This parameter does not apply to routes that are already in the IP route
table. The default administrative distance for static IP routes is 1.
The default metric and administrative distance values ensure that the Layer 3 Switch always
prefers static IP routes over routes from other sources to the same destination.
Multiple static routes to the same destination provide load sharing and
redundancy
You can add multiple static routes for the same destination network to provide one or more of the
following benefits:
• IP load balancing – When you add multiple IP static routes for the same destination to different
next-hop gateways, and the routes each have the same metric and administrative distance, the
Layer 3 Switch can load balance traffic to the routes’ destination. For information about IP
load balancing, refer to “Configuring IP load sharing” on page 605.
• Path redundancy – When you add multiple static IP routes for the same destination, but give
the routes different metrics or administrative distances, the Layer 3 Switch uses the route with
the lowest administrative distance by default, but uses another route to the same destination if
the first route becomes unavailable.
Refer to the following sections for examples and configuration information:
• “Configuring load balancing and redundancy using multiple static routes to the same
destination” on page 600
• “Configuring standard static IP routes and interface or null static routes to the same
destination” on page 601
Static route states follow port states
IP static routes remain in the IP route table only so long as the port or virtual interface used by the
route is available. If the port or virtual routing interface becomes unavailable, the software
removes the static route from the IP route table. If the port or virtual routing interface becomes
available again later, the software adds the route back to the route table.
This feature allows the Layer 3 Switch to adjust to changes in network topology. The Layer 3 Switch
does not continue trying to use routes on unavailable paths but instead uses routes only when their
paths are available.