The Juniper BGP router must be configured to limit the prefix size on any inbound route advertisement to /24 or the least significant prefixes issued to the customer.

The effects of prefix deaggregation can degrade router performance due to the size of routing tables and also result in black-holing legitimate traffic. Initiated by an attacker or a misconfigured router, prefix deaggregation occurs when the announcement of a large prefix is fragmented into a collection of smaller prefix announcements.

This requirement is not applicable for the DODIN Backbone. Review the router configuration to verify that there is a filter to reject inbound route advertisements that are greater than /24, or the least significant prefixes issued to the customer, whichever is larger. Verify each BGP neighbor implements an import policy. BGP import policies are supported in three locations: Global (at [edit protocols bgp]), group (at [edit protocols bgp group <name>]), and for each neighbor (at [edit protocols bgp group <name> neighbor <neighbor address>]) with the most specific import statement being applied. Multiple policy statements may be necessary to address each customer's requirements. [edit policy-options] policy-statement reject-long-prefixes { term 1 { from { route-filter 0.0.0.0/0 prefix-length-range /25-/32; } then reject; } <additional terms> } [edit protocols] bgp { group <group name> { type external; import <policy statement name>; << Applied instead of global BGP policy unless a more specific neighbor import filter exists. Excludes all terms in the global filter. local-as <local AS number>; neighbor <neighbor 1 address> { import <policy statement name>; << Most specific import filter. If configured, only this filter applies to this neighbor (all other terms in all other filters ignored). authentication-key "$8$aes256-gcm$hmac-sha2-256$100$cFQ99Gy83Og$SCMVXvnfna7/cZqH9fCECQ$bCVokm+es94xFJONmbKFNA$4561Uc/r"; ## SECRET-DATA } neighbor <neighbor 2 address> { import <policy statement name>; << Most specific import filter. If configured, only this filter applies to this neighbor (all other terms in all other filters ignored). ipsec-sa <SA name>; } } import <policy statement name>; << Least specific import filter. } If the router is not configured to limit the prefix size on any inbound route advertisement to /24 or the least significant prefixes issued to the customer, this is a finding.

Configure all eBGP routers to use the prefix limit feature to protect against route table flooding and prefix deaggregation attacks. set policy-options policy-statement <statement name> term 1 from route-filter 0.0.0.0/0 prefix-length-range /25-/32 set policy-options policy-statement <statement name> term 1 then reject set protocols bgp group <group name> type external set protocols bgp group <group name> import <statement name> set protocols bgp group <group name> local-as <local AS number> set protocols bgp group <group name> neighbor <neighbor 1 address> import <statement name> set protocols bgp group <group name> neighbor <neighbor 1 address> authentication-key <PSK value> set protocols bgp group <group name> neighbor <neighbor 2 address> import <statement name> set protocols bgp group <group name> neighbor <neighbor 2 address> ipsec-sa <SA name> set protocols bgp import <statement name>