CISC-RT-000530 - The Cisco BGP switch must be configured to reject outbound route advertisements for any prefixes belonging to the IP core.

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Information

Outbound route advertisements belonging to the core can result in traffic either looping or being black holed, or at a minimum, using a nonoptimized path.

Solution

Step 1: Configure a prefix list for containing all customer and local AS prefixes as shown in the example below:

R1(config)#ip prefix-list FILTER_CORE_PREFIXES deny x.1.1.0/24 le 32
R1(config)#ip prefix-list FILTER _CORE_PREFIXES deny x.1.2.0/24 le 32
R1(config)#ip prefix-list FILTER _CORE_PREFIXES permit 0.0.0.0/0 ge 8

Step 2: Apply the prefix list filter outbound to each CE neighbor as shown in the example.

router bgp xx
address-family ipv4
neighbor x.1.4.12 prefix-list FILTER _CORE_PREFIXES out

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-001097, Rule-ID|SV-221027r929070_rule, STIG-ID|CISC-RT-000530, STIG-Legacy|SV-110875, STIG-Legacy|V-101771, Vuln-ID|V-221027

Plugin: Cisco

Control ID: 596b3ed3e31e8dcdbc81f581602441768cab12b837beaea28358f50757192034