OS10 Enterprise Edition User Guide Release 10.4.1.0

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enforce-first-as

Enforces the first AS in the AS path of the route received from an EBGP peer to be the same as the configured remote AS.

Syntax
enforce-first-as
Parameters
None
Default
Enabled
Command Mode
ROUTER-BGP
Usage Information
To verify statistics of routes rejected, use the show ip bgp neighbors command. If routes are rejected, the session is reset. In the event of a failure, the existing BGP sessions flap. For updates received from EBGP peers, BGP ensures that the first AS of the first AS segment is always the AS of the peer, otherwise the update drops and the counter increments. The no version of this command turns off the default.
  • NOTE: To configure these settings for a non default VRF instance, you must first enter the ROUTER-CONFIG-VRF sub mode using the following commands:
    1. Enter the ROUTER BGP mode using the router bgp as-number command.
    2. From the ROUTER BGP mode, enter the ROUTER BGP VRF mode using the vrf vrf-name command.
Example
OS10(conf-router-bgp-1)# enforce-first-as
Supported Releases
10.3.0E or later

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