CISC-RT-000550 - The Cisco BGP router must be configured to reject route advertisements from CE routers with an originating AS in the AS_PATH attribute that does not belong to that customer.

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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 routers must be configured to reject routes with an originating AS other than that belonging to the customer.

Solution

This requirement is not applicable for the DODIN Backbone.

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

Step 1: Configure an inbound route policy for each customer to only accept routes with an originating AS that belongs to that customer as shown in the example below.

RP/0/0/CPU0:R2(config)#route-policy FILTER_64514_ROUTES
RP/0/0/CPU0:R2(config-rpl)#if as-path originates-from '64514' then
RP/0/0/CPU0:R2(config-rpl-if)#pass
RP/0/0/CPU0:R2(config-rpl-if)#else
RP/0/0/CPU0:R2(config-rpl-else)#drop
RP/0/0/CPU0:R2(config-rpl-else)#endif
RP/0/0/CPU0:R2(config-rpl)#end-policy
RP/0/0/CPU0:R2(config)#route-policy FILTER_64516_ROUTES
RP/0/0/CPU0:R2(config-rpl)#if as-path originates-from '64516' then
RP/0/0/CPU0:R2(config-rpl-if)#pass
RP/0/0/CPU0:R2(config-rpl-if)#else
RP/0/0/CPU0:R2(config-rpl-else)#drop
RP/0/0/CPU0:R2(config-rpl-else)#endif
RP/0/0/CPU0:R2(config-rpl)#end-policy

Step 2: Apply the appropriate inbound route policy with each peering CE router as shown in the example below.

RP/0/0/CPU0:R2(config)#router bgp xx
RP/0/0/CPU0:R2(config-bgp)#neighbor x.12.4.14
RP/0/0/CPU0:R2(config-bgp-nbr)#address-family ipv4 unicast
RP/0/0/CPU0:R2(config-bgp-nbr-af)#route-policy route-policy FILTER_64514_ROUTES in
RP/0/0/CPU0:R2(config-bgp)#neighbor x.12.4.16
RP/0/0/CPU0:R2(config-bgp-nbr)#address-family ipv4 unicast
RP/0/0/CPU0:R2(config-bgp-nbr-af)#route-policy FILTER_64516_ROUTES in
RP/0/0/CPU0:R2(config-bgp-nbr-af)#end

See Also

https://dl.dod.cyber.mil/wp-content/uploads/stigs/zip/U_Cisco_IOS-XR_Router_Y21M04_STIG.zip

Item Details

Category: ACCESS CONTROL

References: 800-53|AC-4(8), CAT|III, CCI|CCI-000032, Rule-ID|SV-216783r531087_rule, STIG-ID|CISC-RT-000550, STIG-Legacy|SV-105911, STIG-Legacy|V-96773, Vuln-ID|V-216783

Plugin: Cisco

Control ID: c1b48a5e66655fdc42cb889fb1d087d7ae666442668965b3be520103b1ba2017