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V-221108

CAT III (Low)

The Cisco BGP switch must be configured to reject route advertisements from BGP peers that do not list their autonomous system (AS) number as the first AS in the AS_PATH attribute.

Rule ID

SV-221108r1137898_rule

STIG

Cisco NX OS Switch RTR Security Technical Implementation Guide

Version

V3R4

CCIs

CCI-000032

Discussion

Verifying the path a route has traversed will ensure the IP core is not used as a transit network for unauthorized or possibly even internet traffic. All autonomous system boundary switches (ASBRs) must ensure updates received from eBGP peers list their AS number as the first AS in the AS_PATH attribute.

Check Content

Review the switch configuration to verify the switch is configured to deny updates received from eBGP peers that do not list their AS number as the first AS in the AS_PATH attribute.

By default Cisco IOS enforces the first AS in the AS_PATH attribute for all route advertisements. Review the switch configuration to verify that the command no enforce-first-as is not configured.

router bgp xx
 router-id 10.1.1.1
 no enforce-first-as

If the switch is not configured to reject updates from peers that do not list their AS number as the first AS in the AS_PATH attribute, this is a finding.

Fix Text

Configure the switch to deny updates received from eBGP peers that do not list their AS number as the first AS in the AS_PATH attribute.

SW1(config)# router bgp xx
SW1(config-router)# enforce-first-as
SW1(config-router)# end