V-254048

Discussion

When Proxy ARP is enabled on a router, it allows that router to extend the network (at layer 2) across multiple interfaces (LAN segments). Because proxy ARP allows hosts from different LAN segments to look like they are on the same segment, proxy ARP is only safe when used between trusted LAN segments. Attackers can leverage the trusting nature of proxy ARP by spoofing a trusted host and then intercepting packets. Proxy ARP should always be disabled on router interfaces that do not require it, unless the router is being used as a LAN bridge.

Check Content

This requirement is not applicable for the DODIN Backbone.

Review the router configuration to determine if Proxy ARP is disabled on all external interfaces. By default, Proxy ARP is disabled on all interfaces. Verify "proxy-arp" has not been enabled on external interfaces as shown in the example:

[edit interfaces]
<external interface> {
    unit 0 {
        proxy-arp [restricted|unrestricted]; << Must not be configured on external interfaces.
        <additional configuration>
    }
}

If Proxy ARP is enabled on any external interface, this is a finding.