STIGQter: STIG Summary: Cisco IOS XR Router RTR Security Technical Implementation Guide Version: 2 Release: 1 Benchmark Date: 23 Oct 2020:

The Cisco BGP router must be configured to reject outbound route advertisements for any prefixes belonging to the IP core.

DISA Rule

SV-216781r531087_rule

Vulnerability Number

V-216781

Group Title

SRG-NET-000205-RTR-000006

Rule Version

CISC-RT-000530

Severity

CAT II

CCI(s)

• CCI-001097 - The information system monitors and controls communications at the external boundary of the information system and at key internal boundaries within the system.

Weight

10

Fix Recommendation

Step 1: Configure a prefix set containing the IP core prefix as shown below.

RP/0/0/CPU0:R2(config)#prefix-set

Step 2: Configure a prefix set containing the current Bogon prefixes as shown below.

RP/0/0/CPU0:R2(config)#prefix-set CORE_PREFIX
RP/0/0/CPU0:R2(config-pfx)#10.1.1.0/24 le 32
RP/0/0/CPU0:R2(config-pfx)#end-set

Step 3: Configure the route policy to drop route advertisements for IP core prefixes as shown in the example below.

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

Step 4: Apply the route policy to each external BGP neighbor as shown in the example.

RP/0/0/CPU0:R2(config)#router bgp xx
RP/0/0/CPU0:R2(config-bgp)#neighbor x.1.23.3
RP/0/0/CPU0:R2(config-bgp-nbr)#address-family ipv4 unicast
RP/0/0/CPU0:R2(config-bgp-nbr-af)#route-policy BGP_FILTER_OUTBOUND out
RP/0/0/CPU0:R2(config-bgp)#neighbor x.1.24.4
RP/0/0/CPU0:R2(config-bgp-nbr)#address-family ipv4 unicast
RP/0/0/CPU0:R2(config-bgp-nbr-af)#route-policy BGP_FILTER_ OUTBOUND out

Check Contents

Step 1: verify that an outbound route policy has been configured for each external neighbor as shown in the example below.

router bgp xx
address-family ipv4 unicast
!
neighbor x.1.23.3
remote-as yy
address-family ipv4 unicast
route-policy BGP_FILTER_OUTBOUND out
!
!
neighbor x.1.24.4
remote-as zz
address-family ipv4 unicast
route-policy BGP_FILTER_OUTBOUND out
!
!

Step 2: Review the route policy to determine if it is filtering at a minimum IP core prefixes as shown in the example below.

route-policy BGP_FILTER_OUTBOUND
if destination in CORE_PREFIX then
drop
else
pass
endif
end-policy

Step 3: Review the prefix set referenced in the route policy above to determine if it includes the IP core prefix as shown in the example below.

prefix-set CORE_PREFIX
10.1.1.0/24 le 32
end-set

If the router is not configured to reject outbound route advertisements for prefixes belonging to the IP core, this is a finding.

Vulnerability Number

V-216781

Documentable

False

Rule Version

CISC-RT-000530

Severity Override Guidance

Step 1: verify that an outbound route policy has been configured for each external neighbor as shown in the example below.

router bgp xx
address-family ipv4 unicast
!
neighbor x.1.23.3
remote-as yy
address-family ipv4 unicast
route-policy BGP_FILTER_OUTBOUND out
!
!
neighbor x.1.24.4
remote-as zz
address-family ipv4 unicast
route-policy BGP_FILTER_OUTBOUND out
!
!

Step 2: Review the route policy to determine if it is filtering at a minimum IP core prefixes as shown in the example below.

route-policy BGP_FILTER_OUTBOUND
if destination in CORE_PREFIX then
drop
else
pass
endif
end-policy

Step 3: Review the prefix set referenced in the route policy above to determine if it includes the IP core prefix as shown in the example below.

prefix-set CORE_PREFIX
10.1.1.0/24 le 32
end-set

If the router is not configured to reject outbound route advertisements for prefixes belonging to the IP core, this is a finding.

Check Content Reference

M

Target Key

4029

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