Configuration Guide User guide

788 BigIron RX Series Configuration Guide
53-1002484-04
Configuring OSPF
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The <secs> parameter specifies the number of seconds and can be from 10 – 1800 (30 minutes).
The default is 240 seconds (four minutes).
To restore the pacing interval to its default value, enter the following command.
BigIron RX(config-ospf-router)# no timers lsa-group-pacing 20
OSPF ABR type 3 LSA filtering
OSPF ABR Type 3 LSA filtering increases the ability of an ABR that is running the OSPF protocol to
filter type 3 link-state advertisements (LSAs) that are sent between different OSPF areas. Only
packets with specified prefixes will be sent from one area to another area and prohibits all packets
with other prefixes.
Type 3 LSAs refer to summary links and are sent by ABRs to advertise destinations outside the
area. OSPF ABR Type 3 LSA filtering gives the administrator improved control of route distribution
between OSPF areas.
Usage and configuration guidelines
• The “area prefix-list” command is only applicable to the ABRs. If the router is not an ABR
the configuration is accepted however it will start working only after router is made ABR.
• With this feature enabled in the “in” direction, all type 3 LSAs originated by the ABR to this
area, based on information from all other areas, are filtered by the prefix list. Type 3 LSAs
that were originated as a result of the area range command in another area are treated
like any other type 3 LSA that was originated individually. Any prefix that does not match an
entry in the prefix list is implicitly denied.
• With this feature enabled in the “out” direction, all type 3 LSAs advertised by the ABR,
based on information from this area to all other areas, are filtered by the prefix list. If the
area range command has been configured for this area, Type 3 LSAs that corresponds to
the area range command are treated like any other type 3 LSA.
• Prefixes that are not permitted by the prefix list are implicitly denied.
• The following table displays the behavior for prefix list configurations
TABLE 122 Behavior for prefix list configurations
IP prefix list OSPF area prefix list Event Filtering done
XXX Not defined None No (permit all)
Not defined Defined None Yes (deny all)
Not defined Defined IP prefix list defined Recalculation
Defined (no rules
configured)
Defined None Implicit deny (deny all)
Defined (rules
configured)
Defined IP prefix list deleted Recalculation and deny all
Defined (rules
configured)
Defined IP prefix list rule added or
modified or deleted
Recalculation
Defined (rules
configured)
Defined Area prefix list deleted Recalculation and permit all