The router must protect perimeter routers connected to an Alternate Gateway by configuring an inbound filter that only permits packets with destination addresses within the site's address space.

Overview

Finding ID	Version	Rule ID	IA Controls	Severity
SRG-NET-000019-RTR-000009	SRG-NET-000019-RTR-000009	SRG-NET-000019-RTR-000009_rule		Medium

Description
Enclave's with Alternate Gateway connections must take additional steps to ensure there is no compromise on the enclave network or NIPRNet. Without verifying the destination address of traffic coming from the site's Alternate Gateway, the perimeter router could be routing transit data from the Internet into the NIPRNet. This could also make the perimeter router vulnerable to a DoS attack as well as provide a backdoor into the NIPRNet. The DoD enclave must ensure the ingress filter applied to external interfaces on a perimeter router connecting to an Approved Gateway is secure through filters permitting packets with a destination address belonging to the DoD enclave's address block.

Description

Enclave's with Alternate Gateway connections must take additional steps to ensure there is no compromise on the enclave network or NIPRNet. Without verifying the destination address of traffic coming from the site's Alternate Gateway, the perimeter router could be routing transit data from the Internet into the NIPRNet. This could also make the perimeter router vulnerable to a DoS attack as well as provide a backdoor into the NIPRNet. The DoD enclave must ensure the ingress filter applied to external interfaces on a perimeter router connecting to an Approved Gateway is secure through filters permitting packets with a destination address belonging to the DoD enclave's address block.

STIG	Date
Router Security Requirements Guide	2013-07-30

Details

Check Text ( C-SRG-NET-000019-RTR-000009_chk )
Review the configuration of each router interface connecting to an Alternate Gateway. Verify each permit statement of the ingress filter only permits packets with destination addresses of the site's NIPRNet address space or a destination address belonging to the address block assigned by the Alternate Gateway network service provider. If the ingress filter permits packets with other addresses other than specified, such as destination addresses of the site's NIPRNet address space or a destination address belonging to the address block assigned by the Alternate Gateway network service provider, this is a finding.

Check Text ( C-SRG-NET-000019-RTR-000009_chk )

Review the configuration of each router interface connecting to an Alternate Gateway. Verify each permit statement of the ingress filter only permits packets with destination addresses of the site's NIPRNet address space or a destination address belonging to the address block assigned by the Alternate Gateway network service provider. If the ingress filter permits packets with other addresses other than specified, such as destination addresses of the site's NIPRNet address space or a destination address belonging to the address block assigned by the Alternate Gateway network service provider, this is a finding.

Fix Text (F-SRG-NET-000019-RTR-000009_fix)
Configure the ingress filter of the perimeter router connected to an Alternate Gateway to only permit packets with destination addresses of the site's NIPRNet address space or a destination address belonging to the address block assigned by the Alternate Gateway network service provider.