CISC-RT-000520 - The Cisco BGP router must be configured to reject outbound route advertisements for any prefixes that do not belong to any customers or the local autonomous system (AS).

Information

Advertisement of routes by an autonomous system for networks that do not belong to any of its customers pulls traffic away from the authorized network. This causes a denial of service (DoS) on the network that allocated the block of addresses and may cause a DoS on the network that is inadvertently advertising it as the originator. It is also possible that a misconfigured or compromised router within the GIG IP core could redistribute IGP routes into BGP, thereby leaking internal routes.

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

Solution

This requirement is not applicable for the DODIN Backbone.

Step 1: Configure a prefix set for customer and local autonomous system prefixes as shown in the example.

RP/0/0/CPU0:R2(config)#prefix-set CE_PREFIX_ADVERTISEMENTS
RP/0/0/CPU0:R2(config-pfx)#x.13.1.0/24 le 32,
RP/0/0/CPU0:R2(config-pfx)#x.13.2.0/24 le 32,
RP/0/0/CPU0:R2(config-pfx)#x.13.3.0/24 le 32,
RP/0/0/CPU0:R2(config-pfx)#x.13.4.0/24 le 32
RP/0/0/CPU0:R2(config-pfx)#end-set

Step 2: Configure a route policy filter for allow customer and local autonomous system prefixes as shown in the example.

RP/0/0/CPU0:R2(config)#route-policy CE_ADVERTISEMENTS
RP/0/0/CPU0:R2(config-rpl)#if destination in CE_PREFIX_ADVERTISEMENTS then
RP/0/0/CPU0:R2(config-rpl-if)#pass
RP/0/0/CPU0:R2(config-rpl-if)#else
RP/0/0/CPU0:R2(config-rpl-else)#drop
RP/0/0/CPU0:R2(config-rpl-else)#endif
RP/0/0/CPU0:R2(config-rpl)#end-policy

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

RP/0/0/CPU0:R2(config)#router bgp xx
RP/0/0/CPU0:R2(config-bgp)#neighbor x.12.4.14
RP/0/0/CPU0:R2(config-bgp-nbr)#address-family ipv4 unicast
RP/0/0/CPU0:R2(config-bgp-nbr-af)#route-policy route-policy CE_ADVERTISEMENTS out
RP/0/0/CPU0:R2(config-bgp)#neighbor x.12.4.16
RP/0/0/CPU0:R2(config-bgp-nbr)#address-family ipv4 unicast
RP/0/0/CPU0:R2(config-bgp-nbr-af)#route-policy CE_ADVERTISEMENTS out
RP/0/0/CPU0:R2(config-bgp-nbr-af)#end

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-216780r531087_rule, STIG-ID|CISC-RT-000520, STIG-Legacy|SV-105905, STIG-Legacy|V-96767, Vuln-ID|V-216780

Plugin: Cisco

Control ID: 5ba48954cfbdf7b76b8d9bfa3bb2b295e3921ab7822e859d6f0652947ad53c70