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.

NOTE: Nessus has provided the target output to assist in reviewing the benchmark to ensure target compliance.

Solution

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

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

RP/0/0/CPU0:R2(config)#prefix-set BOGON_PREFIXES
RP/0/0/CPU0:R2(config-pfx)#0.0.0.0/8 le 32,
RP/0/0/CPU0:R2(config-pfx)#10.0.0.0/8 le 32,
RP/0/0/CPU0:R2(config-pfx)#100.64.0.0/10 le 32,
RP/0/0/CPU0:R2(config-pfx)#127.0.0.0/8 le 32,
RP/0/0/CPU0:R2(config-pfx)#169.254.0.0/16 le 32,
RP/0/0/CPU0:R2(config-pfx)#172.16.0.0/12 le 32,
RP/0/0/CPU0:R2(config-pfx)#192.0.2.0/24 le 32,
RP/0/0/CPU0:R2(config-pfx)#192.88.99.0/24 le 32,
RP/0/0/CPU0:R2(config-pfx)#192.168.0.0/16 le 32,
RP/0/0/CPU0:R2(config-pfx)#198.18.0.0/15 le 32,
RP/0/0/CPU0:R2(config-pfx)#198.51.100.0/24 le 32,
RP/0/0/CPU0:R2(config-pfx)#203.0.113.0/24 le 32,
RP/0/0/CPU0:R2(config-pfx)#240.0.0.0/4 le 32,
RP/0/0/CPU0:R2(config-pfx)#224.0.0.0/4 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
RP/0/0/CPU0:R2(config-rpl)#if destination in BOGON_PREFIXES 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 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 in

See Also

https://dl.dod.cyber.mil/wp-content/uploads/stigs/zip/U_Cisco_NX-OS_Switch_Y24M10_STIG.zip

Item Details

Category: ACCESS CONTROL

References: 800-53|AC-4, CAT|II, CCI|CCI-001368, Rule-ID|SV-216777r531087_rule, STIG-ID|CISC-RT-000490, STIG-Legacy|SV-105899, STIG-Legacy|V-96761, Vuln-ID|V-216777

Plugin: Cisco

Control ID: f0fafefa27a992fba78cb5c412d12b2c963deccd3752e01915ffad8980682579