Review the firewall filter for the router receive path and verify that it will only process specific management plane and control plane traffic from specific sources. For example:
[edit policy-options]
auth_mgt_networks-ipv4 {
<IPv4 subnet / mask>;
}
auth_mgt_networks-ipv6 {
<IPv6 subnet / prefix>;
}
device_mgt_address-ipv4 {
<IPv4 address>/32;
}
device_mgt_address-ipv6 {
<IPv6 address>/128;
}
[edit firewall]
family inet {
filter protect_re-ipv4 {
term 1 {
from {
source-prefix-list auth_mgt_networks-ipv4;
destination-prefix-list device_mgt_address-ipv4;
<additional match criteria>;
}
}
<additional permit terms>
term default {
then {
log;
syslog;
discard;
}
}
}
}
family inet6 {
filter protect_re-ipv6 {
term 1 {
from {
source-prefix-list auth_mgt_networks-ipv6;
destination-prefix-list device_mgt_address-ipv6;
<additional match criteria>;
}
}
<additional permit terms>
term default {
then {
log;
syslog;
discard;
}
}
}
}
Note: Additional match criteria includes protocol (next-header for IPv6), source and destination ports, ICMP type and code, etc. When applied to the loopback interface, the filter affects identified traffic regardless of ingress interface. Ensure the filter addresses all traffic destined to the RE like routing protocols, ICMP messages, SSH and SCP traffic, SNMP, etc.
Verify filters are applied to loopback, all L3 interfaces, or both. For example:
[edit interfaces]
lo0 {
unit 0 {
family inet {
filter {
input protect_re-ipv4;
}
address <IPv4 address>/32;
}
family inet6 {
filter {
input protect_re-ipv6;
}
address <IPv6 address>/32;
}
}
}
Note: Some Juniper devices support both monolithic filters and filter lists. Filter lists separate each term, or set of terms, into a separate filter that is applied sequentially to an interface. If using filter lists, the keywords "input" or "output" change to "input-list" or "output-list". Verify the final list item is a deny-all filter. The deny-all filter is created once per family and can be reused across multiple lists. For example:
input-list [ permit_mgt permit_routing_protocols default-deny ];
If the router is not configured with a receive-path filter to restrict traffic destined to itself, this is a finding.
Note: If the platform does not support the receive path filter, verify that all layer 3 interfaces have an ingress firewall filter to control what packets are allowed to be destined to the router for processing.