Detections
Analytics
1.33 CISC-RT-000520
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This audit has been deprecated and will be removed in a future update.
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The Cisco BGP switch must be configured to reject outbound route advertisements for any prefixes that do not belong to any customers or the local autonomous system (AS).GROUP ID: V-221106
RULE ID: SV-221106r999715
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 switch within the GIG IP core could redistribute Interior Gateway Protocol (IGP) routes into BGP, thereby leaking internal routes.
Solution
Step 1 : Configure a prefix list for containing all customer and local AS prefixes as shown in the example below:SW1(config)#ip prefix-list CE_PREFIX_ADVERTISEMENTS permit x.13.1.0/24 le 32
SW1(config)#ip prefix-list CE_PREFIX_ADVERTISEMENTS permit x.13.2.0/24 le 32
SW1(config)#ip prefix-list CE_PREFIX_ADVERTISEMENTS permit x.13.3.0/24 le 32
SW1(config)#ip prefix-list CE_PREFIX_ADVERTISEMENTS permit x.13.4.0/24 le 32
...
...
...
SW1(config)#ip prefix-list CE_PREFIX_ADVERTISEMENTS deny 0.0.0.0/0 ge 8
Step 2 : Apply the prefix list filter outbound to each CE neighbor as shown in the example below:
SW1(config)#switch bgp 64512
SW1(config-switch)# neighbor x.12.4.14 prefix-list CE_PREFIX_ADVERTISEMENTS out
SW1(config-switch)# neighbor x.12.4.16 prefix-list CE_PREFIX_ADVERTISEMENTS out
See Also
Item Details
Audit Name: CIS Cisco NX OS Switch RTR STIG v1.0.0 CAT II
Category: ACCESS CONTROL
References: 800-53|AC-4, CAT|II, CCI|CCI-001368, CSCv7|13.3, Rule-ID|SV-221106r999715_rule, STIG-ID|CISC-RT-000520, Vuln-ID|V-221106
Plugin: Cisco
Control ID: 0d88e6645dd7beeb7df4ab24d51f6c39fbe6e97819bdc5be5cb0d6d86b2eaffd