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).
Severity | Group ID | Group Title | Version | Rule ID | Date | STIG Version |
|---|---|---|---|---|---|---|
| medium | V-216600 | SRG-NET-000018-RTR-000005 | CISC-RT-000520 | SV-216600r917414_rule | 2024-11-25 | 3 |
| Description |
|---|
| 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. |
| ℹ️ Check |
|---|
| This requirement is not applicable for the DODIN Backbone. Step 1: Verify that a prefix list has been configured containing prefixes belonging to customers as well as the local AS as shown in the example below. ip prefix-list CE_PREFIX_ADVERTISEMENTS seq 5 permit x.13.1.0/24 le 32 ip prefix-list CE_PREFIX_ADVERTISEMENTS seq 10 permit x.13.2.0/24 le 32 ip prefix-list CE_PREFIX_ADVERTISEMENTS seq 15 permit x.13.3.0/24 le 32 ip prefix-list CE_PREFIX_ADVERTISEMENTS seq 20 permit x.13.4.0/24 le 32 … … … ip prefix-list CE_PREFIX_ADVERTISEMENTS seq 80 deny 0.0.0.0/0 ge 8 Step 2: Verify that the prefix lists has been applied to all CE peers as shown in the example below. router bgp 64512 no synchronization bgp log-neighbor-changes neighbor x.12.4.14 remote-as 64514 neighbor x.12.4.14 prefix-list CE_PREFIX_ADVERTISEMENTS out neighbor x.12.4.16 remote-as 64516 neighbor x.12.4.16 prefix-list CE_PREFIX_ADVERTISEMENTS out If the router is not configured to reject outbound route advertisements that do not belong to any customers or the local AS, this is a finding. Note: This check is NA for JRSS systems. |
| ✔️ Fix |
|---|
| This requirement is not applicable for the DODIN Backbone. 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 CE_PREFIX_ADVERTISEMENTS permit x.13.1.0/24 le 32 R1(config)#ip prefix-list CE_PREFIX_ADVERTISEMENTS permit x.13.2.0/24 le 32 R1(config)#ip prefix-list CE_PREFIX_ADVERTISEMENTS permit x.13.3.0/24 le 32 R1(config)#ip prefix-list CE_PREFIX_ADVERTISEMENTS permit x.13.4.0/24 le 32 … … … R1(config)#ip prefix-list CE_PREFIX_ADVERTISEMENTS deny 0.0.0.0/0 ge 8 |