Juniper

overload in OSPF in JUNOS

Posted on April 30, 2009. Filed under: Juniper, ospf, overload |

Configure the Router to Appear Overloaded

You can configure the local router so that it appears to be overloaded. You might do this when you want the router to participate in OSPF routing, but do not want it to be used for transit traffic. (Note that traffic to immediately attached interfaces continues to transit the router.)

You configure or disable overload mode in OSPF with or without a timeout. Without a timeout, overload mode is set until it is explicitly deleted from the configuration. With a timeout, overload mode is set if the time elapsed since the OSPF instance started is less than the specified timeout.

A timer is started for the difference between the timeout and the time elapsed since the instance started. When the timer expires, overload mode is cleared. In overload mode, the router LSA is originated with all the transit router links (except stub) set to a metric of 0xFFFF. The stub router links are advertised with the actual cost of the interfaces corresponding to the stub. This causes the transit traffic to avoid the overloaded router and take paths around the router. However, the overloaded router’s own links are still accessible.

To mark the router as overloaded, include the overload statement at the [edit protocols (ospf | ospf3)] hierarchy level (for routing instances, include the statement at the [edit routing-instances routing-instance-name protocols ospf] hierarchy level):

[edit protocols (ospf | ospf3)]

overload;

To specify the number of seconds at which overload is reset, include the timeout option when specifying the overload statement:

[edit protocols (ospf | ospf3)]

overload timeout <seconds>;

The time can be a value from 60 through 1800 seconds.