neighbor allowas-in

Disables the AS_PATH check function for routes learned from a specified neighbor so that BGP does not reject routes that contain the recipient BGP speaker's AS number.

Syntax

neighbor { ip-address | ipv6-address | peer-group-name } allowas-in number

no neighbor allowas-in { ip-address | ipv6-address | peer-group-name } allowas-in

Command Default

The AS_PATH check function is enabled and any route whose path contains the speaker's AS number is rejected as a loop.

Parameters

ip-address: Specifies the IP address of the neighbor.
ipv6-address: Specifies the IPv6 address of the neighbor.
peer-group-name: Specifies a peer group.
number: Specifies the number of times that the AS path of a received route may contain the recipient BGP speaker's AS number and still be accepted. Valid values are 1 through 10.

Modes

BGP address-family IPv4 unicast configuration mode

BGP address-family IPv6 unicast configuration mode

BGP address-family IPv4 unicast VRF configuration mode

BGP address-family IPv6 unicast VRF configuration mode

BGP address-family L2VPN EVPN configuration mode

Usage Guidelines

If the AS_PATH check function is disabled after a BGP session has been established, the neighbor session must be cleared for this change to take effect.

The no form of the command re-enables the AS_PATH check function.

Examples

The following example specifies that the AS path of a received route may contain the recipient BGP4+ speaker's AS number three times and still be accepted.

device# configure terminal
device(config)# router bgp
device(config-bgp-router)# address-family ipv6 unicast
device(config-bgp-ipv6u)# neighbor 2001:2018:8192::125 allowas-in 3
%Warning: Please clear the neighbor session for the parameter change to take effect!

The following example specifies for VRF instance "red" that the BGP4+ AS path of a received route may contain the recipient BGP speaker's AS number three times and still be accepted.

device# configure terminal
device(config)# router bgp
device(config-bgp-router)# address-family ipv6 unicast vrf red
device(config-bgp-ipv6u-vrf)# neighbor 2001:2018:8192::124 allowas-in 3
%Warning: Please clear the neighbor session for the parameter change to take effect!

The following example specifies that the AS path of a received route may contain the recipient BGP speaker's AS number three times and still be accepted in L2VPN EVPN configuration mode.

device# configure terminal
device(config)# router bgp
device(config-bgp-router)# address-family l2vpn evpn
device(config-bgp-evpn)# neighbor 10.1.1.1 allowas-in 3
%Warning: Please clear the neighbor session for the parameter change to take effect!

The following example specifies that the AS path of a received IPv6 route from the neighbor 20.0.0.1 may contain the recipient BGP4+ speaker's AS number up to three (3) times and can still be accepted.

device# configure terminal
device(config)# router bgp
device(config-bgp-router)# address-family ipv6 unicast
device(config-bgp-ipv6u)# neighbor 20.0.0.1 allowas-in 3
%Warning: Please clear the neighbor session for the parameter change to take effect!