ECS4660-28F_Management Guide-R03

C HAPTER 51 | IP Routing Commands
Border Gateway Protocol (BGPv4)
– 1839 –
◆ Prefix lists are checked starting from the lowest sequence number and
continues through the list until a match is found. Once an entry is found
that covers a network, the permit or deny statement is applied to that
network, and the search process stops.
◆ At least one “permit” statement should be included when more than
one entry is defined. Commonly used “Deny” statements can be
included at the top of the list to quickly remove unsuitable routing
messages. If a list includes all “Deny” statements, then an entry of
“permit 0.0.0.0 255.255.255.255 ge 0 le 32” can be included at the
bottom of the list to grant passage for all other routing messages.
◆ A prefix list can be applied to inbound or outbound updates for a
specific peer by entering the neighbor prefix-list command, or with the
match ip address prefix-list route map command to implement a more
comprehensive filter for policy-based routing.
EXAMPLE
This example denies access to routing messages for the specified address.
Console(config)#ip prefix-list LS deny 10.0.0.0 255.0.0.0 ge 14 le 22
Console(config)#
RELATED COMMANDS
neighbor prefix-list (1873)
match ip address (1904)
aggregate-address This command configures an aggregate address in the routing table. Use
the no form to delete an aggregate address.
SYNTAX
[no] aggregate-address ip-address netmask [as-set]
[summary-only]
ip-address – An IPv4 address expressed in dotted decimal notation.
netmask – Network mask for the route. This mask identifies the
network address bits used for the associated routing entries.
as-set – Generates autonomous system set information for the AS
path attribute, indicating that a route originated in multiple
autonomous systems.
summary-only – Sends the summary routes only, ignoring more
specific routes.
COMMAND MODE
Router Configuration
DEFAULT SETTING
No aggregate routes are defined.