STIGQter: STIG Summary: Cisco NX-OS Switch RTR Security Technical Implementation Guide Version: 2 Release: 1 Benchmark Date: 23 Apr 2021:

The Cisco BGP switch must be configured to reject inbound route advertisements for any Bogon prefixes.

DISA Rule

SV-221103r622190_rule

Vulnerability Number

V-221103

Group Title

SRG-NET-000018-RTR-000002

Rule Version

CISC-RT-000490

Severity

CAT II

CCI(s)

• CCI-001368 - The information system enforces approved authorizations for controlling the flow of information within the system based on organization-defined information flow control policies.

Weight

10

Fix Recommendation

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

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

SW1(config)# ip prefix-list PREFIX_FILTER seq 5 deny 0.0.0.0/8 le 32
SW1(config)# ip prefix-list PREFIX_FILTER seq 10 deny 10.0.0.0/8 le 32
SW1(config)# ip prefix-list PREFIX_FILTER seq 15 deny 100.64.0.0/10 le 32
SW1(config)# ip prefix-list PREFIX_FILTER seq 20 deny 127.0.0.0/8 le 32
SW1(config)# ip prefix-list PREFIX_FILTER seq 25 deny 169.254.0.0/16 le 32
SW1(config)# ip prefix-list PREFIX_FILTER seq 30 deny 172.16.0.0/12 le 32
SW1(config)# ip prefix-list PREFIX_FILTER seq 35 deny 192.0.2.0/24 le 32
SW1(config)# ip prefix-list PREFIX_FILTER seq 40 deny 192.88.99.0/24 le 32
SW1(config)# ip prefix-list PREFIX_FILTER seq 45 deny 192.168.0.0/16 le 32
SW1(config)# ip prefix-list PREFIX_FILTER seq 50 deny 198.18.0.0/15 le 32
SW1(config)# ip prefix-list PREFIX_FILTER seq 55 deny 198.51.100.0/24 le 32
SW1(config)# ip prefix-list PREFIX_FILTER seq 60 deny 203.0.113.0/24 le 32
SW1(config)# ip prefix-list PREFIX_FILTER seq 65 deny 224.0.0.0/4 le 32
SW1(config)# ip prefix-list PREFIX_FILTER seq 70 deny 240.0.0.0/4 le 32
SW1(config)# ip prefix-list PREFIX_FILTER seq 75 permit 0.0.0.0/0 ge 8

Step 2: Apply the prefix list filter inbound to each external BGP neighbor as shown in the example below:

SW1(config)# router bgp xx
SW1(config-router)# neighbor x.1.12.2
SW1(config-router-neighbor)# address-family ipv4 unicast
SW1(config-router-neighbor-af)# prefix-list PREFIX_FILTER in
SW1(config-router-neighbor-af)# exit
SW1(config-router-neighbor)# exit
SW1(config-router)# neighbor x.2.44.4
SW1(config-router-neighbor)# address-family ipv4 unicast
SW1(config-router-neighbor-af)# prefix-list PREFIX_FILTER in
SW1(config-router-neighbor-af)# end

Route Map Alternative

Step 1: Configure the route map referencing the configured prefix list above.

SW1(config)# route-map FILTER_PREFIX_MAP permit 10
SW1(config-route-map)# match ip address prefix-list PREFIX_FILTER
SW1(config-route-map)# exit

Step 2: Apply the route-map inbound to each external BGP neighbor as shown in the example below:

SW1(config)# router bgp xx
SW1(config-router)# neighbor x.1.12.2
SW1(config-router-neighbor)# address-family ipv4 unicast
SW1(config-router-neighbor-af)# route-map FILTER_PREFIX_MAP in
SW1(config-router-neighbor-af)# exit
SW1(config-router-neighbor)# exit
SW1(config-router)# neighbor x.2.44.4
SW1(config-router-neighbor)# address-family ipv4 unicast
SW1(config-router-neighbor-af)# route-map FILTER_PREFIX_MAP in
SW1(config-router-neighbor-af)# end

Check Contents

Review the switch configuration to verify that it will reject BGP routes for any Bogon prefixes.

Step 1: Verify a prefix list has been configured containing the current Bogon prefixes as shown in the example below:

ip prefix-list PREFIX_FILTER seq 5 deny 0.0.0.0/8 le 32
ip prefix-list PREFIX_FILTER seq 10 deny 10.0.0.0/8 le 32
ip prefix-list PREFIX_FILTER seq 15 deny 100.64.0.0/10 le 32
ip prefix-list PREFIX_FILTER seq 20 deny 127.0.0.0/8 le 32
ip prefix-list PREFIX_FILTER seq 25 deny 169.254.0.0/16 le 32
ip prefix-list PREFIX_FILTER seq 30 deny 172.16.0.0/12 le 32
ip prefix-list PREFIX_FILTER seq 35 deny 192.0.2.0/24 le 32
ip prefix-list PREFIX_FILTER seq 40 deny 192.88.99.0/24 le 32
ip prefix-list PREFIX_FILTER seq 45 deny 192.168.0.0/16 le 32
ip prefix-list PREFIX_FILTER seq 50 deny 198.18.0.0/15 le 32
ip prefix-list PREFIX_FILTER seq 55 deny 198.51.100.0/24 le 32
ip prefix-list PREFIX_FILTER seq 60 deny 203.0.113.0/24 le 32
ip prefix-list PREFIX_FILTER seq 65 deny 224.0.0.0/4 le 32
ip prefix-list PREFIX_FILTER seq 70 deny 240.0.0.0/4 le 32
ip prefix-list PREFIX_FILTER seq 75 permit 0.0.0.0/0 ge 8

Step 2: Verify that the prefix list has been applied to all external BGP peers as shown in the example below:

router bgp xx
router-id 10.1.1.1
neighbor x.1.12.2 remote-as xx
password 3 7b07d1b3023056a9
address-family ipv4 unicast
prefix-list PREFIX_FILTER in
neighbor x.2.44.4 remote-as xx
password 3 f07a10cb41db8bb6f8f0a340049a9b02
address-family ipv4 unicast
prefix-list PREFIX_FILTER in

Route Map Alternative

Verify that the route map applied to the external neighbors references the configured Bogon prefix list shown above.

route-map FILTER_PREFIX_MAP permit 10
match ip address prefix-list PREFIX_FILTER
…
…
…
router bgp xx
router-id 10.1.1.1
neighbor x.1.12.2 remote-as xx
password 3 7b07d1b3023056a9
address-family ipv4 unicast
route-map FILTER_PREFIX_MAP in
neighbor x.2.44.4 remote-as xx
password 3 f07a10cb41db8bb6f8f0a340049a9b02
address-family ipv4 unicast
route-map FILTER_PREFIX_MAP in

If the switch is not configured to reject inbound route advertisements for any Bogon prefixes, this is a finding.

Vulnerability Number

V-221103

Documentable

False

Rule Version

CISC-RT-000490

Severity Override Guidance

Review the switch configuration to verify that it will reject BGP routes for any Bogon prefixes.

Step 1: Verify a prefix list has been configured containing the current Bogon prefixes as shown in the example below:

ip prefix-list PREFIX_FILTER seq 5 deny 0.0.0.0/8 le 32
ip prefix-list PREFIX_FILTER seq 10 deny 10.0.0.0/8 le 32
ip prefix-list PREFIX_FILTER seq 15 deny 100.64.0.0/10 le 32
ip prefix-list PREFIX_FILTER seq 20 deny 127.0.0.0/8 le 32
ip prefix-list PREFIX_FILTER seq 25 deny 169.254.0.0/16 le 32
ip prefix-list PREFIX_FILTER seq 30 deny 172.16.0.0/12 le 32
ip prefix-list PREFIX_FILTER seq 35 deny 192.0.2.0/24 le 32
ip prefix-list PREFIX_FILTER seq 40 deny 192.88.99.0/24 le 32
ip prefix-list PREFIX_FILTER seq 45 deny 192.168.0.0/16 le 32
ip prefix-list PREFIX_FILTER seq 50 deny 198.18.0.0/15 le 32
ip prefix-list PREFIX_FILTER seq 55 deny 198.51.100.0/24 le 32
ip prefix-list PREFIX_FILTER seq 60 deny 203.0.113.0/24 le 32
ip prefix-list PREFIX_FILTER seq 65 deny 224.0.0.0/4 le 32
ip prefix-list PREFIX_FILTER seq 70 deny 240.0.0.0/4 le 32
ip prefix-list PREFIX_FILTER seq 75 permit 0.0.0.0/0 ge 8

Step 2: Verify that the prefix list has been applied to all external BGP peers as shown in the example below:

router bgp xx
router-id 10.1.1.1
neighbor x.1.12.2 remote-as xx
password 3 7b07d1b3023056a9
address-family ipv4 unicast
prefix-list PREFIX_FILTER in
neighbor x.2.44.4 remote-as xx
password 3 f07a10cb41db8bb6f8f0a340049a9b02
address-family ipv4 unicast
prefix-list PREFIX_FILTER in

Route Map Alternative

Verify that the route map applied to the external neighbors references the configured Bogon prefix list shown above.

route-map FILTER_PREFIX_MAP permit 10
match ip address prefix-list PREFIX_FILTER
…
…
…
router bgp xx
router-id 10.1.1.1
neighbor x.1.12.2 remote-as xx
password 3 7b07d1b3023056a9
address-family ipv4 unicast
route-map FILTER_PREFIX_MAP in
neighbor x.2.44.4 remote-as xx
password 3 f07a10cb41db8bb6f8f0a340049a9b02
address-family ipv4 unicast
route-map FILTER_PREFIX_MAP in

If the switch is not configured to reject inbound route advertisements for any Bogon prefixes, this is a finding.

Check Content Reference

M

Target Key

4075

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