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In BGP route-map configuration, the continue clause allows for more programmable policy configuration and route filtering and introduced the capability to execute additional entries in a route map after an entry is executed with successful match and set clauses. Continue clauses allow you to configure and organize more modular policy definitions so that specific policy configurations need not be repeated within the same route map. Before the continue clause was introduced, route-map configuration was linear and did not allow any control over the flow of a route map.

Perform this task to filter traffic using continue clauses in a BGP route map.

Note	Continue clauses can go only to a higher route map entry (a route map entry with a higher sequence number) and cannot go to a lower route map entry.

1.    enable


2.    configure terminal


3.    router bgp autonomous-system-number


4.    neighbor {ip-address| peer-group-name} remote-as autonomous-system-number


5.    neighbor {ip-address| peer-group-name} route-map map-name {in | out}


6.    exit


7.    route-map map-name {permit | deny} [sequence-number]


8.    match ip address {access-list-number | access-list-name} [... access-list-number | ... access-list-name]


9.    set community community-number [additive] [well-known-community] | none}


10.    continue [sequence-number]


11.    end


12.    show route-map [map-name]

Device> enable

Device# configure terminal

Device(config)# router bgp 50000

Device(config-router)# neighbor 10.0.0.1 remote-as 50000

Device(config-router)# neighbor 10.0.0.1 route-map ROUTE-MAP-NAME in

Device(config-router)# exit

Device(config)# route-map ROUTE-MAP-NAME permit 10

Device(config-route-map)# match ip address 1

Device(config-route-map)# set community 10:1

Device(config-route-map)# continue

Device(config-route-map)# end

Device# show route-map

Device# show route-map

route-map MARKETING, permit, sequence 10
  Match clauses:
    ip address (access-lists): 1 
    metric 10 
  Continue: sequence 40
  Set clauses:
    as-path prepend 10
  Policy routing matches: 0 packets, 0 bytes
route-map MARKETING, permit, sequence 20
  Match clauses:
    ip address (access-lists): 2 
    metric 20 
  Set clauses:
    as-path prepend 10 10
  Policy routing matches: 0 packets, 0 bytes
route-map MARKETING, permit, sequence 30
  Match clauses:
  Continue: to next entry 40
  Set clauses:
    as-path prepend 10 10 10
  Policy routing matches: 0 packets, 0 bytes
route-map MARKETING, permit, sequence 40
  Match clauses:
    community (community-list filter): 10:1 
  Set clauses:
    local-preference 104
  Policy routing matches: 0 packets, 0 bytes
route-map MKTG-POLICY-MAP, permit, sequence 10
  Match clauses:
  Set clauses:
    community 655370
  Policy routing matches: 0 packets, 0 bytes

The following example shows continue clause configuration in a route map sequence.

Note	Continue clauses in outbound route maps are supported only in Cisco IOS Release 12.0(31)S, 12.2(33)SB, 12.2(33)SRB, 12.2(33)SXI, 12.4(4)T, and later releases.

The first continue clause in route map entry 10 indicates that the route map will go to route map entry 30 if a successful matches occurs. If a match does not occur, the route map will “fall through” to route map entry 20. If a successful match occurs in route map entry 20, the set action will be executed and the route map will not evaluate any additional route map entries. Only the first successful match ip address clause is supported.

If a successful match does not occur in route map entry 20, the route map will fall through to route map entry 30. This sequence does not contain a match clause, so the set clause will be automatically executed and the continue clause will go to the next route map entry because a sequence number is not specified.

If there are no successful matches, the route map will fall through to route map entry 30 and execute the set clause. A sequence number is not specified for the continue clause, so route map entry 40 will be evaluated.

There are two behaviors that can occur when the same set command is repeated in subsequent continue clause entries. For set commands that configure an additive or accumulative value (for example, set community additive, set extended community additive, and set as-path prepend), subsequent values are added by subsequent entries. The following example illustrates this behavior. After each set of match clauses, a set as-path prepend command is configured to add an autonomous system number to the as-path. After a match occurs, the route map stops evaluating match clauses and starts executing the set clauses, in the order in which they were configured. Depending on how many successful match clauses occur, the as-path is prepended by one, two, or three autonomous system numbers.

route-map ROUTE-MAP-NAME permit 10
 match ip address 1
 match metric 10
 set as-path prepend 10
 continue 30
 !
route-map ROUTE-MAP-NAME permit 20
 match ip address 2
 match metric 20
 set as-path prepend 10 10
 !
route-map ROUTE-MAP-NAME permit 30
 set as-path prepend 10 10 10
 continue
 !
route-map ROUTE-MAP-NAME permit 40
 match community 10:1
 set local-preference 104

In this example, the same set command is repeated in subsequent continue clause entries, but the behavior is different from the first example. For set commands that configure an absolute value, the value from the last instance will overwrite the previous value(s). The following example illustrates this behavior. The set clause value in sequence 20 overwrites the set clause value from sequence 10. The next hop for prefixes from the 172.16/16 network is set to 10.2.2.2, not 10.1.1.1.

ip prefix-list 1 permit 172.16.0.0/16 
ip prefix-list 2 permit 192.168.1.0/24 
route-map RED permit 10 
 match ip address prefix-list 1 
 set ip next hop 10.1.1.1 
 continue 20 
 exit 
route-map RED permit 20 
 match ip address prefix-list 2 
 set ip next hop 10.2.2.2 
 end 

Note	Route maps have a linear behavior and not a nested behavior. Once a route is matched in a route map permit entry with a continue command clause, it will not be processed by the implicit deny at the end of the route-map. The following example illustrates this case.

In the following example, when routes match an as-path of 10, 20, or 30, the routes are permitted and the continue clause jumps over the explicit deny clause to process the match ip address prefix list. If a match occurs here, the route metric is set to 100. Only routes that do not match an as-path of 10, 20, or 30 and do match a community number of 30 are denied. To deny other routes, you must configure an explicit deny statement.

route-map test permit 10
 match as-path 10 20 30
 continue 30
 exit
route-map test deny 20
 match community 30
 exit
route-map test permit 30
 match ip address prefix-list 1
 set metric 100
 exit