Supported Platforms
Understanding Route Preference Values
The Junos OS routing protocol process assigns a default preference value (also known as an administrative distance) to each route that the routing table receives. The default value depends on the source of the route. The preference value is a value from 0 through 4,294,967,295 (232 – 1), with a lower value indicating a more preferred route. Table 1 lists the default preference values.
Table 1: Default Route Preference Values
How Route Is Learned | Default Preference | Statement to Modify Default Preference |
|---|---|---|
Directly connected network | 0 | – |
System routes | 4 | – |
Static and Static LSPs | 5 | |
RSVP-signaled LSPs | 7 | RSVP preference as described in the Junos OS MPLS Applications Configuration Guide |
LDP-signaled LSPs | 9 | LDP preference, as described in the Junos OS MPLS Applications Configuration Guide |
OSPF internal route | 10 | OSPF preference |
IS-IS Level 1 internal route | 15 | IS-IS preference |
IS-IS Level 2 internal route | 18 | IS-IS preference |
Redirects | 30 | – |
Kernel | 40 | – |
SNMP | 50 | – |
Router discovery | 55 | – |
RIP | 100 | RIP preference |
RIPng | 100 | RIPng preference |
PIM | 105 | |
DVMRP | 110 | |
Aggregate | 130 | |
OSPF AS external routes | 150 | OSPF external-preference |
IS-IS Level 1 external route | 160 | IS-IS external-preference |
IS-IS Level 2 external route | 165 | IS-IS external-preference |
BGP | 170 | BGP preference, export, import |
MSDP | 175 |
In general, the narrower the scope of the statement, the higher precedence its preference value is given, but the smaller the set of routes it affects. To modify the default preference value for routes learned by routing protocols, you generally apply routing policy when configuring the individual routing protocols. You also can modify some preferences with other configuration statements, which are indicated in the table.
