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This chapter describes the Cisco NX-OS Border Gateway Protocol (BGP) commands that begin with A.
To enter IPv6 unicast address family mode, use the address-family ipv6 unicast command.
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This example shows how enter IPv6 unicast address family mode:
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Filters prefixes advertised in type 3 link-state advertisements (LSAs) between Open Shortest Path First (OSPF) areas of an Area Border Router (ABR). |
To enter the neighbor address family mode address-family mode and configure submode commands for the Border Gateway Protocol (BGP), use the address-family command. To disable the address family submode for configuring routing protocols, use the no form of this command.
address-family ipv4 { multicast | unicast }
no address-family ipv4 { multicast | unicast }
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Use the address-family command to enter various address family configuration modes while configuring BGP routing. When you enter the address-family command from neighbor configuration mode, you enable the neighbor address family and enter the neighbor address family configuration mode. The prompt changes to switch(config-router-neighbor-af)#.
You must configure the address families if you are using route redistribution, load balancing, and other advanced features. IPv4 neighbor sessions support IPv4 unicast and multicast address families.
From the neighbor address family configuration mode, the following parameters are available:
Note This applies to IPv4 multicast or unicast
This example shows how to activate IPv4 multicast for neighbor 192.0.2.1 and place the device in neighbor address family configuration mode for the IPv4 multicast address family:
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Configures a BGP routing process to distribute a default route. |
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Configures the switch software to start storing BGP peer updates. |
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To enter the address family mode or a virtual routing and forwarding (VRF) address-family mode and configure submode commands for the Border Gateway Protocol (BGP), use the address-family command. To disable the address family submode for configuring routing protocols, use the no form of this command.
address-family ipv4 { multicast | unicast }
no address-family ipv4 { multicast | unicast }
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Use the address-family command to enter various address family configuration modes while configuring BGP routing. When you enter the address-family command from router configuration mode, you enable the address family and enter global address family configuration mode. The prompt changes to switch(config-router-af)#.
You must configure the address families if you are using route redistribution, address aggregation, load balancing, and other advanced features. IPv4 neighbor sessions support IPv4 unicast and multicast address families.
From the address family configuration mode, the following parameters are available:
Note This applies to IPv4 multicast or unicast.
Note When enabled, the default-metric command applies a metric value of 0 to redistributed connected routes. The default-metric command does not override metric values that are applied with the redistribute command.
– direct route-map name —Specifies directly connected routes.
– eigrp AS-num route-map name —Specifies Enhanced Interior Gateway Protocol routes. Range: 1 to 65535.
– ospf src-protocol route-map name —Specifies Open Shortest Path First (OSPF) routes.
– rip src-protocol route-map name —Specifies Routing Information Protocol (RIP) routes.
This example shows how to place the router in global address family configuration mode for the IPv4 unicast address family:
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Configures the default metric for routes redistributed into BGP. |
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Configures the BGP delay for triggering next-hop calculations. |
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To configure Border Gateway Protocol (BGP) conditional advertisement, use the advertise-map command. To remove BGP conditional advertisement, use the no form of this command.
advertise-map adv-map { exist-map exist-rmap | non-exist-map nonexist-rmap }
no advertise-map adv-map { exist-map exist-rmap | non-exist-map nonexist-rmap }
BGP neighbor address-family configuration mode
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Use the advertise-map command to conditionally advertise selected routes. The routes or prefixes that BGP conditionally advertises are defined in two route maps, the adv-map and an exist-map or nonexist-map. The e xist-map or nonexist-map specifies the prefix that the BGP tracks. The adv-map specifies the prefix that BGP advertises to the specified neighbor when the condition is met.
This example shows how to configure BGP conditional advertisement:
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To create a summary address in a Border Gateway Protocol (BGP) routing table, use the aggregate-address command. To remove the summary address, use the no form of this command.
aggregate-address address / length [ advertise-map map-name ] [ as-set ] [ attribute-map map-name ] [ summary-only ] [ suppress-map map-name ]
no aggregate-address address / mask-length [ advertise-map map-name ] [ as-set ] [ attribute-map map-name ] [ summary-only ] [ suppress-map map-name ]
The atomic aggregate attribute is set automatically when an aggregate route is created with this command unless the as-set keyword is specified.
Address family configuration mode
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You can implement aggregate routing in BGP either by redistributing an aggregate route into BGP, or by using the conditional aggregate routing feature.
The aggregate-address command without keywords creates an aggregate entry in the BGP routing table if any more-specific BGP routes are available that fall within the specified range. (A longer prefix which matches the aggregate must exist in the RIB.) The aggregate route will be advertised as coming from your autonomous system and will have the atomic aggregate attribute set to show that information might be missing. (By default, the atomic aggregate attribute is set unless you specify the as-set keyword.)
The as-set keyword creates an aggregate entry using the same rules that the command follows without this keyword, but the path advertised for this route will be an AS_SET consisting of all elements contained in all paths that are being summarized. Do not use this form of the aggregate-address command when aggregating many paths, because this route must be continually withdrawn and updated as autonomous system path reachability information for the summarized routes changes.
The summary-only keyword not only creates the aggregate route (for example, 192.*.*.*) but also suppresses advertisements of more-specific routes to all neighbors. If you want to suppress only advertisements to certain neighbors, you may use the neighbor distribute-list command, with caution. If a more-specific route leaks out, all BGP routers will prefer that route over the less-specific aggregate you are generating (using longest-match routing).
The suppress-map keyword creates the aggregate route but suppresses advertisement of specified routes. You can use the match clauses of route maps to selectively suppress some more-specific routes of the aggregate and leave others unsuppressed. IP access lists and autonomous system path access lists match clauses are supported.
The advertise-map keyword selects specific routes that will be used to build different components of the aggregate route, such as AS_SET or community. This form of the aggregate-address command is useful when the components of an aggregate are in separate autonomous systems and you want to create an aggregate with AS_SET, and advertise it back to some of the same autonomous systems. You must remember to omit the specific autonomous system numbers from the AS_SET to prevent the aggregate from being dropped by the BGP loop detection mechanism at the receiving router. IP access lists and autonomous system path access lists match clauses are supported.
The attribute-map keyword allows attributes of the aggregate route to be changed. This form of the aggregate-address command is useful when one of the routes forming the AS_SET is configured with an attribute such as the community no-export attribute, which would prevent the aggregate route from being exported. An attribute map route map can be created to change the aggregate attributes.
This example shows how to create an aggregate BGP address in router configuration mode. The path advertised for this route will be an AS_SET consisting of all elements contained in all paths that are being summarized.
This example shows how to create an aggregate BGP address in address family configuration mode and apply it to the multicast database (SAFI) under the IP Version 4 address family. Because the summary-only keyword is configured, more-specific routes are filtered from updates.
Conditional Aggregation Example
This example shows how to create a route map called MAP-ONE to match on an as-path access list. The path advertised for this route will be an AS_SET consisting of elements contained in paths that are matched in the route map.
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