Specifications

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Cisco Nexus 3000 Series NX-OS Unicast Routing Configuration Guide, Release 5.0(3)U2(2)
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Chapter 6 Configuring Advanced BGP
Prerequisites for BGP
Prerequisites for BGP
BGP has the following prerequisites:
• You must enable the BGP feature (see the “Enabling the BGP Feature” section on page 5-11).
• You should have a valid router ID configured on the system.
• You must have an AS number, either assigned by a Regional Internet Registry (RIR) or locally
administered.
• You must have reachability (such as an interior gateway protocol (IGP), a static route, or a direct
connection) to the peer that you are trying to make a neighbor relationship with.
• You must explicitly configure an address family under a neighbor for the BGP session
establishment.
Guidelines and Limitations for BGP
BGP has the following configuration guidelines and limitations:
• The dynamic AS number prefix peer configuration overrides the individual AS number
configuration inherited from a BGP template.
• If you configure a dynamic AS number for prefix peers in an AS confederation, BGP establishes
sessions with only the AS numbers in the local confederation.
• BGP sessions created through a dynamic AS number prefix peer ignore any configured eBGP
multihop time-to-live (TTL) value or a disabled check for directly connected peers.
• Configure a router ID for BGP to avoid automatic router ID changes and session flaps.
• Use the maximum-prefix configuration option per peer to restrict the number of routes received and
system resources used.
• Configure the update-source to establish a session with eBGP multihop sessions.
• Specify a BGP route map if you configure redistribution.
• Configure the BGP router ID within a VRF.
• If you decrease the keepalive and hold timer values, the network might experience session flaps.
Default Settings
Table 6-1 lists the default settings for BGP parameters.
Product License Requirement
Cisco NX-OS BGP requires an LAN Enterprise Services license. For a complete explanation of the Cisco NX-OS licensing
scheme and how to obtain and apply licenses, see the Cisco NX-OS Licensing Guide.
Note Make sure the LAN Base Services license is installed on the switch to enable Layer 3 interfaces.