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 inbound route advertisements for any prefixes belonging to the local autonomous system (AS).

DISA Rule

SV-216778r531087_rule

Vulnerability Number

V-216778

Group Title

SRG-NET-000018-RTR-000003

Rule Version

CISC-RT-000500

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

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

RP/0/0/CPU0:R2(config)#prefix-set Step 1: Configure a prefix set containing the current Bogon prefixes as shown below.

RP/0/0/CPU0:R2(config)#prefix-set LOCAL_PREFIX
RP/0/0/CPU0:R2(config-pfx)#x.13.1.0/24 le 32
RP/0/0/CPU0:R2(config-pfx)#end-set

Step 2: Configure the route policy to drop routes with BOGON prefixes as shown in the example below.

RP/0/0/CPU0:R2(config)#route-policy BGP_FILTER_INBOUND
RP/0/0/CPU0:R2(config-rpl)#if destination in LOCAL_PREFIX then
RP/0/0/CPU0:R2(config-rpl-if)#drop
RP/0/0/CPU0:R2(config-rpl-if)#else pass endif
RRP/0/0/CPU0:R2(config-rpl)#end-policy
RP/0/0/CPU0:R2(config)#exit

Step 3: 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_INBOUND in
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_INBOUND in

Check Contents

Review the router configuration to verify that it will reject routes belonging to the local AS.

Step 1: verify that an inbound 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
keychain YYY_KEY_CHAIN
ttl-security
address-family ipv4 unicast
route-policy BGP_FILTER_INBOUND in
!
!
neighbor x.1.24.4
remote-as zz
keychain ZZZ_KEY_CHAIN
ttl-security
address-family ipv4 unicast
route-policy BGP_FILTER_INBOUND in
!
!

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

route-policy BGP_FILTER_INBOUND
if destination in LOCAL_PREFIX then
drop
else
pass
endif
end-policy

Note: If bogons are also filtered per previous requirement, the route policy would look similar to the following example:

route-policy BGP_FILTER_INBOUND
if destination in BOGON_PREFIXES then
drop
elseif destination in LOCAL_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 local global prefix as shown in the example below.

prefix-set LOCAL_PREFIX
x.13.1.0/24 le 32
end-set

If the router is not configured to reject inbound route advertisements belonging to the local AS, this is a finding.

Vulnerability Number

V-216778

Documentable

False

Rule Version

CISC-RT-000500

Severity Override Guidance

Review the router configuration to verify that it will reject routes belonging to the local AS.

Step 1: verify that an inbound 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
keychain YYY_KEY_CHAIN
ttl-security
address-family ipv4 unicast
route-policy BGP_FILTER_INBOUND in
!
!
neighbor x.1.24.4
remote-as zz
keychain ZZZ_KEY_CHAIN
ttl-security
address-family ipv4 unicast
route-policy BGP_FILTER_INBOUND in
!
!

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

route-policy BGP_FILTER_INBOUND
if destination in LOCAL_PREFIX then
drop
else
pass
endif
end-policy

Note: If bogons are also filtered per previous requirement, the route policy would look similar to the following example:

route-policy BGP_FILTER_INBOUND
if destination in BOGON_PREFIXES then
drop
elseif destination in LOCAL_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 local global prefix as shown in the example below.

prefix-set LOCAL_PREFIX
x.13.1.0/24 le 32
end-set

If the router is not configured to reject inbound route advertisements belonging to the local AS, this is a finding.

Check Content Reference

M

Target Key

4029

Comments