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

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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 switch to reject inbound route advertisements for any Bogon prefixes.

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

SW1(config)#ip prefix-list PREFIX_FILTER deny 0.0.0.0/8 le 32
SW1(config)#ip prefix-list PREFIX_FILTER deny 10.0.0.0/8 le 32
SW1(config)#ip prefix-list PREFIX_FILTER deny 100.64.0.0/10 le 32
SW1(config)#ip prefix-list PREFIX_FILTER deny 127.0.0.0/8 le 32
SW1(config)#ip prefix-list PREFIX_FILTER deny 169.254.0.0/16 le 32
SW1(config)#ip prefix-list PREFIX_FILTER deny 172.16.0.0/12 le 32
SW1(config)#ip prefix-list PREFIX_FILTER deny 192.0.2.0/24 le 32
SW1(config)#ip prefix-list PREFIX_FILTER deny 192.88.99.0/24 le 32
SW1(config)#ip prefix-list PREFIX_FILTER deny 192.168.0.0/16 le 32
SW1(config)#ip prefix-list PREFIX_FILTER deny 198.18.0.0/15 le 32
SW1(config)#ip prefix-list PREFIX_FILTER deny 198.51.100.0/24 le 32
SW1(config)#ip prefix-list PREFIX_FILTER deny 203.0.113.0/24 le 32
SW1(config)#ip prefix-list PREFIX_FILTER deny 224.0.0.0/4 le 32
SW1(config)#ip prefix-list PREFIX_FILTER deny 240.0.0.0/4 le 32
SW1(config)#ip prefix-list PREFIX_FILTER deny 240.0.0.0/4 le 32
SW1(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:

SW1(config)#router bgp xx
SW1(config-switch)#neighbor x.1.1.9 prefix-list PREFIX_FILTER in
SW1(config-switch)#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.

SW1(config)#route-map FILTER_PREFIX_MAP 10
SW1(config-route-map)#match ip address prefix-list PREFIX_FILTER
SW1(config-route-map)#exit

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

SW1(config)#router bgp xx
SW1(config-switch)#neighbor x.1.1.9 route-map FILTER_PREFIX_MAP in
SW1(config-switch)#neighbor x.2.1.7 route-map FILTER_PREFIX_MAP in
SW1(config-switch)#end

See Also

https://dl.dod.cyber.mil/wp-content/uploads/stigs/zip/U_Cisco_IOS-XE_Switch_Y24M04_STIG.zip

Item Details

References: CAT|II, CCI|CCI-001368, Rule-ID|SV-221023r622190_rule, STIG-ID|CISC-RT-000490, STIG-Legacy|SV-110867, STIG-Legacy|V-101763, Vuln-ID|V-221023

Plugin: Cisco

Control ID: 37ec367c141d6dfe086249a5114c68f3832fcb33bcf10a7e92e05932b248224f