CISC-RT-000500 - The Cisco BGP router must be configured to reject inbound route advertisements for any prefixes belonging to the local autonomous system (AS) - neighbor

Information

Accepting route advertisements belonging to the local AS can result in traffic looping or being black holed, or at a minimum using a non-optimized path.

Solution

Step 1: Configure a prefix set containing the current Bogon prefixes as shown below.

RP/0/0/CPU0:R2(config)#prefix-set Step 1: Configure a prefix set containing the current Bogon prefixes as shown below.

RP/0/0/CPU0:R2(config)#prefix-set LOCAL_PREFIX
RP/0/0/CPU0:R2(config-pfx)#x.13.1.0/24 le 32
RP/0/0/CPU0:R2(config-pfx)#end-set

Step 2: Configure the route policy to drop routes with BOGON prefixes as shown in the example below.

RP/0/0/CPU0:R2(config)#route-policy BGP_FILTER_INBOUND
RP/0/0/CPU0:R2(config-rpl)#if destination in LOCAL_PREFIX then
RP/0/0/CPU0:R2(config-rpl-if)#drop
RP/0/0/CPU0:R2(config-rpl-if)#else pass endif
RRP/0/0/CPU0:R2(config-rpl)#end-policy
RP/0/0/CPU0:R2(config)#exit

Step 3: Apply the route policy to each external BGP neighbor as shown in the example.

RP/0/0/CPU0:R2(config)#router bgp xx
RP/0/0/CPU0:R2(config-bgp)#neighbor x.1.23.3
RP/0/0/CPU0:R2(config-bgp-nbr)#address-family ipv4 unicast
RP/0/0/CPU0:R2(config-bgp-nbr-af)#route-policy BGP_FILTER_INBOUND in
RP/0/0/CPU0:R2(config-bgp)#neighbor x.1.24.4
RP/0/0/CPU0:R2(config-bgp-nbr)#address-family ipv4 unicast
RP/0/0/CPU0:R2(config-bgp-nbr-af)#route-policy BGP_FILTER_INBOUND in

See Also

https://dl.dod.cyber.mil/wp-content/uploads/stigs/zip/U_Cisco_IOS-XR_Router_Y24M07_STIG.zip

Item Details

Category: ACCESS CONTROL

References: 800-53|AC-4, CAT|II, CCI|CCI-001368, Rule-ID|SV-216778r531087_rule, STIG-ID|CISC-RT-000500, STIG-Legacy|SV-105901, STIG-Legacy|V-96763, Vuln-ID|V-216778

Plugin: Cisco

Control ID: 2c3543cb40a540e395e4b8302ad4a485b17734a135f329850487ded74e5716ba