Detections
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CISC-RT-000490 - The Cisco BGP router must be configured to reject inbound route advertisements for any Bogon prefixes.

Information

Accepting route advertisements for Bogon prefixes can result in the local autonomous system (AS) becoming a transit for malicious traffic as it will in turn advertise these prefixes to neighbor autonomous systems.

Solution

Configure the router to reject inbound route advertisements for any Bogon prefixes.

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

R1(config)#ip prefix-list PREFIX_FILTER deny 0.0.0.0/8 le 32
R1(config)#ip prefix-list PREFIX_FILTER deny 10.0.0.0/8 le 32
R1(config)#ip prefix-list PREFIX_FILTER deny 100.64.0.0/10 le 32
R1(config)#ip prefix-list PREFIX_FILTER deny 127.0.0.0/8 le 32
R1(config)#ip prefix-list PREFIX_FILTER deny 169.254.0.0/16 le 32
R1(config)#ip prefix-list PREFIX_FILTER deny 172.16.0.0/12 le 32
R1(config)#ip prefix-list PREFIX_FILTER deny 192.0.2.0/24 le 32
R1(config)#ip prefix-list PREFIX_FILTER deny 192.88.99.0/24 le 32
R1(config)#ip prefix-list PREFIX_FILTER deny 192.168.0.0/16 le 32
R1(config)#ip prefix-list PREFIX_FILTER deny 198.18.0.0/15 le 32
R1(config)#ip prefix-list PREFIX_FILTER deny 198.51.100.0/24 le 32
R1(config)#ip prefix-list PREFIX_FILTER deny 203.0.113.0/24 le 32
R1(config)#ip prefix-list PREFIX_FILTER deny 224.0.0.0/4 le 32
R1(config)#ip prefix-list PREFIX_FILTER deny 240.0.0.0/4 le 32
R1(config)#ip prefix-list PREFIX_FILTER deny 240.0.0.0/4 le 32
R1(config)#ip prefix-list PREFIX_FILTER permit 0.0.0.0/0 ge 8

Step 2: Apply the prefix list filter inbound to each external BGP neighbor as shown in the example:

R1(config)#router bgp xx
R1(config-router)#neighbor x.1.1.9 prefix-list PREFIX_FILTER in
R1(config-router)#neighbor x.2.1.7 prefix-list PREFIX_FILTER in

Route Map Alternative:

Step 1: Configure the route map referencing the configured prefix list above.

R1(config)#route-map FILTER_PREFIX_MAP 10
R1(config-route-map)#match ip address prefix-list PREFIX_FILTER
R1(config-route-map)#exit

Step 2: Apply the route-map inbound to each external BGP neighbor as shown in the example:

R1(config)#router bgp xx
R1(config-router)#neighbor x.1.1.9 route-map FILTER_PREFIX_MAP in
R1(config-router)#neighbor x.2.1.7 route-map FILTER_PREFIX_MAP in
R1(config-router)#end

See Also

https://s3.us-gov-west-1.amazonaws.com/dl.dod.cyber.mil/wp-content/uploads/stigs/zip/U_Cisco_IOS-XE_Router_Y25M07_STIG.zip

Item Details

Category: ACCESS CONTROL

References: 800-53|AC-4, CAT|II, CCI|CCI-001368, Rule-ID|SV-216687r877982_rule, STIG-ID|CISC-RT-000490, STIG-Legacy|SV-106085, STIG-Legacy|V-96947, Vuln-ID|V-216687

Plugin: Cisco

Control ID: fe82ac61c86d9cd22cff3e8adc06871fabf7c75e2c61fe85c984b664c6a060fb