The Cisco perimeter router must be configured to not redistribute static routes to an alternate gateway service provider into BGP or an IGP peering with the NIPRNet or to other autonomous systems.

Overview

Finding ID	Version	Rule ID	IA Controls	Severity
V-96557	CISC-RT-000300	SV-105695r1_rule		Low

Description
If the static routes to the alternate gateway are being redistributed into an Exterior Gateway Protocol or Interior Gateway Protocol to a NIPRNet gateway, this could make traffic on NIPRNet flow to that particular router and not to the Internet Access Point routers. This could not only wreak havoc with traffic flows on NIPRNet, but it could overwhelm the connection from the router to the NIPRNet gateway(s) and also cause traffic destined for outside of NIPRNet to bypass the defenses of the Internet Access Points.

Description

If the static routes to the alternate gateway are being redistributed into an Exterior Gateway Protocol or Interior Gateway Protocol to a NIPRNet gateway, this could make traffic on NIPRNet flow to that particular router and not to the Internet Access Point routers. This could not only wreak havoc with traffic flows on NIPRNet, but it could overwhelm the connection from the router to the NIPRNet gateway(s) and also cause traffic destined for outside of NIPRNet to bypass the defenses of the Internet Access Points.

STIG	Date
Cisco IOS Router RTR Security Technical Implementation Guide	2020-06-30

Details

Check Text ( C-95393r1_chk )
This requirement is not applicable for the DODIN Backbone. Step 1: Review the IGP and BGP configurations. If there are redistribute static statements configured as shown in examples below proceed to step 2. OSPF Example router ospf 1 log-adjacency-changes redistribute static subnets network 0.0.0.0 255.255.255.255 area 0 EIGRP example router eigrp 1 network 10.1.15.0 0.0.0.255 redistribute static RIP example router rip version 2 redistribute static network 10.0.0.0 BGP example router bgp nn no synchronization bgp log-neighbor-changes redistribute static neighbor x.11.1.7 remote-as nn neighbor x.11.1.7 password xxxxxxx no auto-summary Step 2: Review the static routes that have been configured to determine if any contain the next hop address of the alternate gateway. If the static routes to the alternate gateway are being redistributed into BGP or any IGP peering to a NIPRNet gateway or any other autonomous system, this is a finding.

Check Text ( C-95393r1_chk )

This requirement is not applicable for the DODIN Backbone.

Step 1: Review the IGP and BGP configurations. If there are redistribute static statements configured as shown in examples below proceed to step 2.

OSPF Example

router ospf 1
log-adjacency-changes
redistribute static subnets
network 0.0.0.0 255.255.255.255 area 0

EIGRP example

router eigrp 1
network 10.1.15.0 0.0.0.255
redistribute static

RIP example

router rip
version 2
redistribute static
network 10.0.0.0

BGP example

router bgp nn
no synchronization
bgp log-neighbor-changes
redistribute static
neighbor x.11.1.7 remote-as nn
neighbor x.11.1.7 password xxxxxxx
no auto-summary

Step 2: Review the static routes that have been configured to determine if any contain the next hop address of the alternate gateway.

If the static routes to the alternate gateway are being redistributed into BGP or any IGP peering to a NIPRNet gateway or any other autonomous system, this is a finding.

Fix Text (F-102231r2_fix)
This requirement is not applicable for the DODIN Backbone. Configure the router so that static routes are not redistributed to an alternate gateway into either a BGP or any IGP peering with the NIPRNet or to any other autonomous systems. This can be done by excluding that route in the route-map as shown in the example below. Step 1: Configure a prefix list for any static routes with the alternate gateway as the next-hop address R5(config)#ip prefix-list ISP_PREFIX permit x.x.x.0/24 Step 2: Configure a route map that will deny the state routes to the ISP R5(config)#route-map FILTER_ISP_STATIC deny 10 R5(config-route-map)#match ip address prefix-list ISP_PREFIX R5(config-route-map)#exit R5(config)#route-map FILTER_ISP_STATIC permit 20 R5(config-route-map)#exit Step 3: Apply the route-map to the IGP and BGP redistribute static commands as shown in the EIGRP example. R5(config)#router eigrp 1 R5(config-router)#redistribute static route-map FILTER_ISP_STATIC

Fix Text (F-102231r2_fix)

This requirement is not applicable for the DODIN Backbone.

Configure the router so that static routes are not redistributed to an alternate gateway into either a BGP or any IGP peering with the NIPRNet or to any other autonomous systems. This can be done by excluding that route in the route-map as shown in the example below.

Step 1: Configure a prefix list for any static routes with the alternate gateway as the next-hop address

R5(config)#ip prefix-list ISP_PREFIX permit x.x.x.0/24

Step 2: Configure a route map that will deny the state routes to the ISP

R5(config)#route-map FILTER_ISP_STATIC deny 10
R5(config-route-map)#match ip address prefix-list ISP_PREFIX
R5(config-route-map)#exit
R5(config)#route-map FILTER_ISP_STATIC permit 20
R5(config-route-map)#exit

Step 3: Apply the route-map to the IGP and BGP redistribute static commands as shown in the EIGRP example.

R5(config)#router eigrp 1
R5(config-router)#redistribute static route-map FILTER_ISP_STATIC