CISC-RT-000550 - The Cisco BGP switch must be configured to reject route advertisements from CE switches with an originating AS in the AS_PATH attribute that does not belong to that customer - ip as-path access-list

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Information

Verifying the path a route has traversed will ensure that the local AS is not used as a transit network for unauthorized traffic. To ensure that the local AS does not carry any prefixes that do not belong to any customers, all PE switches must be configured to reject routes with an originating AS other than that belonging to the customer.

Solution

Configure the switch to reject updates from CE switches with an originating AS in the AS_PATH attribute that does not belong to that customer.

Step 1: Configure the as-path ACL as shown in the example below:

SW1(config)#ip as-path access-list 10 permit ^yy$
SW1(config)#ip as-path access-list 10 deny .*

Step 2: Apply the as-path filter inbound as shown in the example below:

SW1(config)#router bgp xx
SW1(config-switch)#neighbor x.1.4.12 filter-list 10 in

See Also

https://dl.dod.cyber.mil/wp-content/uploads/stigs/zip/U_Cisco_IOS_XE_Switch_Y22M07_STIG.zip

Item Details

References: CAT|III, CCI|CCI-000032, Rule-ID|SV-221029r622190_rule, STIG-ID|CISC-RT-000550, STIG-Legacy|SV-110879, STIG-Legacy|V-101775, Vuln-ID|V-221029

Plugin: Cisco

Control ID: 915d9f99823ad89bcff43b75c49ca2a608362012a9f169f239b7127c46c9d3bb