Is-Is Cli Levels; Global Configuration Level - Dell PowerConnect B-RX Configuration Manual

Route calculation and selection
The Designated IS uses a Shortest Path First (SPF) algorithm to calculate paths to destination ISs
and ESs. The SPF algorithm uses Link State PDUs (LSPDUs) received from other ISs as input, and
creates the paths as output.
After calculating the paths, the Designated IS then selects the best paths and places them in the
IS-IS route table. The Designated IS uses the following process to select the best paths.
1. Prefer the Level-1 path over the Level-2 path.
2. If there is no Level-1 path, prefer the internal Level-2 path over the external Level-2 path.
3. If there is still more than one path, prefer the path with the lowest metric.
4. If there is more than one path with the lowest metric, load share among the paths.
After selecting the best path to a destination, the software places the path in the IS-IS route table.

IS-IS CLI levels

The CLI includes various levels of commands for IS-IS.
FIGURE 119
The IS-IS CLI levels are as follows:
•
•

Global configuration level

You enter the global configuration level of ISIS by entering the following command.
BigIron RX Series Configuration Guide
53-1002253-01
IS-IS CLI levels
router isis
configure terminal
isis interface commands
A global level for the configuration of the IS-IS protocol. At this level, all IS-IS configurations at
this level apply to IPv4 and IPv6. You enter this layer using the router isis command.
•
Under the global level, you specify an address family. Address families to separate the IS-IS
configurations for IPv4 and IPv6. You enter configurations that are for a specific You enter
this level by entering the address-family command at the router isis level.
•
Under the address family level, you select a sub-address family, which is the type of routes
for the configuration. For IS-IS, you specify unicast.
NOTE
IS-IS IPv6 is currently not supported.
An interface level.
Figure 119
Global commands for IS-IS
and all address families
IS-IS CLI levels
diagrams these levels.
IPv6 address-family level
unicast sub-family
IPv4 address-family level
unicast sub-family
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