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Cisco Catalyst Blade Switch 3130 and 3032 for Dell Software Configuration Guide
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Chapter 38 Configuring IP Unicast Routing
Configuring BGP
By default, sequence numbers are generated automatically and incremented in units of five. If you
disable the automatic generation of sequence numbers, you must specify the sequence number for each
entry. You can specify sequence values in any increment. If you specify increments of one, you cannot
insert additional entries into the list. If you choose very large increments, you might run out of values.
You do not need to specify a sequence number when removing a configuration entry.
Show
commands
include the sequence numbers in their output.
Before using a prefix list in a command, you must set up the prefix list. Beginning in privileged EXEC
mode, follow these steps to create a prefix list or to add an entry to a prefix list:
To delete a prefix list and all its entries, use the
no
ip prefix-list
list-name
global configuration
command. To delete an entry from a prefix list, use the
no
ip prefix-list seq
seq-value
global
configuration command. To disable automatic generation of sequence numbers, use the
no ip prefix-list
sequence number
command; to reenable automatic generation, use the
ip prefix-list sequence number
command. To clear the hit-count table of prefix list entries, use the
clear ip prefix-list
privileged EXEC
command.
Configuring BGP Community Filtering
One way that BGP controls the distribution of routing information is based on the value of the
COMMUNITIES attribute. The attribute groups destinations into communities and applies routing
decisions based on the communities. This method simplifies the configuration of a BGP speaker to
control distribution of routing information.
Command
Purpose
Step 1
configure terminal
Enter global configuration mode.
Step 2
ip prefix-list
list-name
[
seq
seq-value
]
deny
|
permit
network
/
len
[
ge
ge-value
] [
le
le-value
]
Create a prefix list with an optional sequence number to
deny
or
permit
access for matching conditions. You must enter at least one
permit
or
deny
clause.
•
network
/
len
is the network number and length (in bits) of the
network mask.
•
(Optional)
ge
and
le
values specify the range of the prefix length
to be matched.The specified
ge-value
and
le-value
must satisfy
this condition:
len
<
ge-value
<
le-value
< 32.
Step 3
ip prefix-list
list-name
seq
seq-value
deny
|
permit
network
/
len
[
ge
ge-value
] [
le
le-value
]
(Optional) Add an entry to a prefix list, and assign a sequence
number to the entry.
Step 4
end
Return to privileged EXEC mode.
Step 5
show ip prefix list
[
detail
|
summary
]
name
[
network
/
len
] [
seq
seq-num
] [
longer
]
[
first-match
]
Verify the configuration by displaying information about a prefix
list or prefix-list entries.
Step 6
copy running-config startup-config
(Optional) Save your entries in the configuration file.