Dell BigIron RX Series, Configuration Manual

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BigIron RX Series Configuration Guide 715
53-1002253-01
Configuring OSPF
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The in keyword specifies that prefix list is applied to prefixes advertised to the specified area from
other areas.
The out keyword specifies that prefix list is applied to prefixes advertised out of the specified area
to other areas.
Defining and applying IP prefix lists
An IP prefix list specifies a list of networks. When you apply an IP prefix list to an area, the BigIron
RX sends or receives only a route whose destination is in the IP prefix list. The software interprets
the prefix lists in order, beginning with the lowest sequence number.
To configure an IP prefix list and apply it to an area, enter commands such as the following.
BigIron RX(config)# ip prefix-list Routesfor20 permit 20.20.0.0/24
BigIron RX(config)# router ospf
BigIron RX(config-ospf-router)#)# area 10.10.10.1 prefix-list Routesfor20 out
These commands configure an IP prefix list named Routesfor20, which permits routes to network
20.20.0.0/24. The area command configures the device to use IP prefix list Routesfor20 to
determine which routes to send to area 10.10.10.1. The device sends routes that go to 20.20.x.x to
area 10.10.10.1 because the IP prefix list explicitly permits these routes to be sent to the area.
Syntax: ip prefix-list <name> [seq <seq-value> ] [description <string> ] deny | permit
<network-addr> / <mask-bits> [ge <ge-value> ] [le <le-value> ]
The <name> parameter specifies the prefix list name. You use this name when applying the prefix
list to a neighbor.
The seq <seq-value> parameter is optional and specifies the IP prefix list’s sequence number. If
you do not specify a sequence number, the software numbers them in increments of 5, beginning
with prefix list entry 5. The software interprets the prefix list entries in numerical order, beginning
with the lowest sequence number.
The description <string> parameter is a text string describing the prefix list.
The deny | permit parameter specifies the action the software takes if a neighbor’s route is in this
prefix list.
The prefix-list matches only on this network unless you use the ge <ge-value> or le <le-value>
parameters. (See below.)
The <network-addr> / <mask-bits> parameter specifies the network number and the number of bits
in the network mask.
You can specify a range of prefix length for prefixes that are more specific than
<network-addr> / <mask-bits> .
•
If you specify only ge <ge-value> , then the mask-length range is from <ge-value> to 32.
•
If you specify only le <le-value> , then the mask-length range is from length to <le-value> .
•
The <ge-value> or <le-value> you specify must meet the following condition.
length < ge-value <= le-value <= 32
If you do not specify ge <ge-value> or le <le-value> , the prefix list matches only on the exact
network prefix you specify with the <network-addr> / <mask-bits> parameter.