Detections
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1.51 CISC-RT-000490

Information

The Cisco BGP router must be configured to reject inbound route advertisements for any Bogon prefixes.

GROUP ID: V-216687
RULE ID: SV-216687r877982

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://workbench.cisecurity.org/benchmarks/26261

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, Vuln-ID|V-216687

Plugin: Cisco

Control ID: 94c813777b2ecc11a02bbb094c22d88e5c91c775a9c1e2030af36633713431ac