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

Overview

Finding ID	Version	Rule ID	IA Controls	Severity
V-217057	JUNI-RT-000520	SV-217057r639663_rule		Medium

Description
Outbound route advertisements belonging to the core can result in traffic either looping or being black holed, or at a minimum, using a non-optimized path.

STIG	Date
Juniper Router RTR Security Technical Implementation Guide	2021-02-11

Details

Check Text ( C-18286r297039_chk )
Review the router configuration to verify that there is a filter defined to block route advertisements for prefixes that belong to the IP core. Verify a prefix list has been configured containing prefixes belonging to the local autonomous system as shown in the example below. policy-options { … … … prefix-list CORE_PREFIX { x.x.x.x/16; } Verify that a policy has been configured to not advertise prefixes belong to the core as shown in the example below. policy-options { … … … policy-statement BGP_ADVERTISE_POLICY { term EXCLUDE_CORE { from { prefix-list CORE_PREFIX; } then reject; } term INCLUDE_OTHER { then accept; } } Verify that the export statement as shown below references the advertise policy. protocols { bgp { group AS4 { type external; export BGP_ADVERTISE_POLICY; peer-as 4; neighbor x.x.x.x; } If the router is not configured to reject outbound route advertisements that belong to the IP core, this is a finding.

Check Text ( C-18286r297039_chk )

Review the router configuration to verify that there is a filter defined to block route advertisements for prefixes that belong to the IP core.

Verify a prefix list has been configured containing prefixes belonging to the local autonomous system as shown in the example below.

policy-options {
…
…
…
prefix-list CORE_PREFIX {
x.x.x.x/16;
}

Verify that a policy has been configured to not advertise prefixes belong to the core as shown in the example below.

policy-options {
…
…
…
policy-statement BGP_ADVERTISE_POLICY {
term EXCLUDE_CORE {
from {
prefix-list CORE_PREFIX;
}
then reject;
}
term INCLUDE_OTHER {
then accept;
}
}

Verify that the export statement as shown below references the advertise policy.

protocols {
bgp {
group AS4 {
type external;
export BGP_ADVERTISE_POLICY;
peer-as 4;
neighbor x.x.x.x;
}

If the router is not configured to reject outbound route advertisements that belong to the IP core, this is a finding.

Fix Text (F-18284r297040_fix)
Configure the router to filter outbound route advertisements belonging to the IP core. Configure a prefix list containing prefixes belonging to the IP core. [edit policy-options] set prefix-list CORE_PREFIX x.x.x.x/16 Configure a policy-statement to filter BGP route advertisements that will exclude core prefixes. [edit policy-options] set policy-statement BGP_ADVERTISE_POLICY term EXCLUDE_CORE from prefix-list CORE_PREFIX set policy-statement BGP_ADVERTISE_POLICY term EXCLUDE_CORE then reject set policy-statement BGP_ADVERTISE_POLICY term INCLUDE_OTHER then accept Configure an export statement referencing the advertise policy on all external BGP peer groups as shown in the example below. [edit protocols bgp group GROUP_AS4] set export BGP_ADVERTISE_POLICY

Fix Text (F-18284r297040_fix)

Configure the router to filter outbound route advertisements belonging to the IP core.

Configure a prefix list containing prefixes belonging to the IP core.

[edit policy-options]
set prefix-list CORE_PREFIX x.x.x.x/16

Configure a policy-statement to filter BGP route advertisements that will exclude core prefixes.

[edit policy-options]
set policy-statement BGP_ADVERTISE_POLICY term EXCLUDE_CORE from prefix-list CORE_PREFIX
set policy-statement BGP_ADVERTISE_POLICY term EXCLUDE_CORE then reject
set policy-statement BGP_ADVERTISE_POLICY term INCLUDE_OTHER then accept

Configure an export statement referencing the advertise policy on all external BGP peer groups as shown in the example below.

[edit protocols bgp group GROUP_AS4]
set export BGP_ADVERTISE_POLICY