Title

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

Discussion

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

Check Content

Review the BGP router configuration to verify that there is a filter defined to block route advertisements for prefixes that belong to the IP core. Verify an appropriate prefix-list containing the IP core prefixes is referenced in a policy-statement. For example: [edit policy-options] prefix-list ip-core-ipv4 { 192.0.2.0/24; } prefix-list ip-core-ipv6 { 2001:db8:2::/64; } policy-statement advertise-bgp-prefix { term exclude-ipv4-core { from { prefix-list ip-core-ipv4; } then reject; } term exclude-ipv6-core { from { prefix-list ip-core-ipv6; } then reject; } term default { then accept; } } The prefix filter must be referenced outbound on the appropriate BGP neighbor statements. For example: [edit protocols] bgp { group eBGP { type external; export advertise-bgp-prefix; neighbor 192.0.2.11 { export advertise-bgp-prefix; } } export advertise-bgp-prefix; } Note: Juniper routers support global, group, and neighbor export statements with the more specific definition taking precedence. Ensure more specific export policies (e.g., neighbor and group) do not reverse higher level export statements. If the router is not configured to reject outbound route advertisements that belong to the IP core, this is a finding.

Fix Text

Configure all eBGP routers to filter outbound route advertisements belonging to the IP core. For example: set policy-options prefix-list ip-core-ipv4 192.0.2.0/24 set policy-options prefix-list ip-core-ipv6 2001:db8:2::/64 set policy-options policy-statement advertise-bgp-prefix term exclude-ipv4-core from prefix-list ip-core-ipv4 set policy-options policy-statement advertise-bgp-prefix term exclude-ipv4-core then reject set policy-options policy-statement advertise-bgp-prefix term exclude-ipv6-core from prefix-list ip-core-ipv6 set policy-options policy-statement advertise-bgp-prefix term exclude-ipv6-core then reject set policy-options policy-statement advertise-bgp-prefix term default then accept set protocols bgp group eBGP type external set protocols bgp group eBGP export advertise-bgp-prefix set protocols bgp group eBGP neighbor 192.0.2.11 export advertise-bgp-prefix set protocols bgp export advertise-bgp-prefix

Additional Identifiers

Rule ID: SV-254015r844078_rule

Vulnerability ID: V-254015

Group Title: SRG-NET-000205-RTR-000006

Expert Comments

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