The Arista BGP router must be configured to reject outbound route advertisements for any prefixes that do not belong to any customers or the local autonomous system (AS).

Overview

Finding ID	Version	Rule ID	IA Controls	Severity
V-255991	ARST-RT-000050	SV-255991r882315_rule		Medium

Description
Advertisement of routes by an autonomous system for networks that do not belong to any of its customers pulls traffic away from the authorized network. This causes a denial of service (DoS) on the network that allocated the block of addresses and may cause a DoS on the network that is inadvertently advertising it as the originator. It is also possible that a misconfigured or compromised router within the GIG IP core could redistribute IGP routes into BGP, thereby leaking internal routes.

Description

Advertisement of routes by an autonomous system for networks that do not belong to any of its customers pulls traffic away from the authorized network. This causes a denial of service (DoS) on the network that allocated the block of addresses and may cause a DoS on the network that is inadvertently advertising it as the originator. It is also possible that a misconfigured or compromised router within the GIG IP core could redistribute IGP routes into BGP, thereby leaking internal routes.

STIG	Date
Arista MLS EOS 4.2x Router Security Technical Implementation Guide	2023-01-17

Details

Check Text ( C-59667r882313_chk )
This requirement is not applicable for the DODIN backbone. Review the Arista router configuration to verify a filter is defined to only advertise routes for prefixes that belong to any customers or the local AS. The prefix filter must be referenced outbound on the appropriate BGP neighbor statements. Step 1: Verify the prefix list is configured on the router and is accepting only prefixes belonging to customers or the local AS prefix (10.12.0.0/16). To verify IP prefix lists are configured, execute the command "show ip prefix-list". ip prefix-list ADVERTISE_ROUTES seq 10 permit 10.12.0.0/16 seq 20 deny 10.17.0.0/16 seq 30 deny 10.23.0.0/16 seq 40 deny 10.47.0.0/16 seq 50 deny 10.59.0.0/16 seq 100 deny 0.0.0.0/0 le 32 Step 2: Verify in the BGP configuration that the filter is applied outbound for each customer to the appropriate BGP neighbor. To verify the BGP config and verify the prefix is applied, execute the command "show run \| section router bgp". router bgp 65001 neighbor 100.2.1.1 prefix-list ADVERTISE_ROUTES out If the Arista router is not configured to reject outbound route advertisements that do not belong to any customers or the local AS, this is a finding.

Check Text ( C-59667r882313_chk )

This requirement is not applicable for the DODIN backbone.

Review the Arista router configuration to verify a filter is defined to only advertise routes for prefixes that belong to any customers or the local AS.

The prefix filter must be referenced outbound on the appropriate BGP neighbor statements.

Step 1: Verify the prefix list is configured on the router and is accepting only prefixes belonging to customers or the local AS prefix (10.12.0.0/16). To verify IP prefix lists are configured, execute the command "show ip prefix-list".

ip prefix-list ADVERTISE_ROUTES
seq 10 permit 10.12.0.0/16
seq 20 deny 10.17.0.0/16
seq 30 deny 10.23.0.0/16
seq 40 deny 10.47.0.0/16
seq 50 deny 10.59.0.0/16
seq 100 deny 0.0.0.0/0 le 32

Step 2: Verify in the BGP configuration that the filter is applied outbound for each customer to the appropriate BGP neighbor. To verify the BGP config and verify the prefix is applied, execute the command "show run | section router bgp".

router bgp 65001
neighbor 100.2.1.1 prefix-list ADVERTISE_ROUTES out

If the Arista router is not configured to reject outbound route advertisements that do not belong to any customers or the local AS, this is a finding.

Fix Text (F-59610r882314_fix)
This requirement is not applicable for the DODIN backbone. Configure all Arista eBGP routers to filter outbound route advertisements for prefixes that are not allocated to or belong to any customer or the local AS. Configure the Arista router to deny outbound route advertisements for any prefix belonging to the local AS Boundary. Step 1: Configure the prefix lists. LEAF-1A(config)#ip prefix-list ADVERTISE_ROUTES LEAF-1A(config-ip-pfx)#seq 10 permit 10.12.0.0/16 LEAF-1A(config-ip-pfx)#seq 20 deny 10.17.0.0/16 LEAF-1A(config-ip-pfx)#seq 30 deny 10.23.0.0/16 LEAF-1A(config-ip-pfx)#seq 40 deny 10.47.0.0/16 LEAF-1A(config-ip-pfx)#seq 50 deny 10.59.0.0/16 LEAF-1A(config-ip-pfx)#seq 100 deny 0.0.0.0/0 le 32 Step 2: Configure the prefix lists outbound to the appropriate BGP neighbor. LEAF-1A(config)#router bgp 65001 LEAF-1A(config-router-bgp)#neighbor 100.2.1.1 prefix-list ADVERTISE_ROUTES out

Fix Text (F-59610r882314_fix)

This requirement is not applicable for the DODIN backbone.

Configure all Arista eBGP routers to filter outbound route advertisements for prefixes that are not allocated to or belong to any customer or the local AS.

Configure the Arista router to deny outbound route advertisements for any prefix belonging to the local AS Boundary.

Step 1: Configure the prefix lists.

LEAF-1A(config)#ip prefix-list ADVERTISE_ROUTES
LEAF-1A(config-ip-pfx)#seq 10 permit 10.12.0.0/16
LEAF-1A(config-ip-pfx)#seq 20 deny 10.17.0.0/16
LEAF-1A(config-ip-pfx)#seq 30 deny 10.23.0.0/16
LEAF-1A(config-ip-pfx)#seq 40 deny 10.47.0.0/16
LEAF-1A(config-ip-pfx)#seq 50 deny 10.59.0.0/16
LEAF-1A(config-ip-pfx)#seq 100 deny 0.0.0.0/0 le 32

Step 2: Configure the prefix lists outbound to the appropriate BGP neighbor.

LEAF-1A(config)#router bgp 65001
LEAF-1A(config-router-bgp)#neighbor 100.2.1.1 prefix-list ADVERTISE_ROUTES out