ARST-RT-000530 - The Arista router must be configured to have Internet Control Message Protocol (ICMP) unreachable notifications disabled on all external interfaces.

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Information

The ICMP supports IP traffic by relaying information about paths, routes, and network conditions. Routers automatically send ICMP messages under a wide variety of conditions. Host unreachable ICMP messages are commonly used by attackers for network mapping and diagnosis.

Solution

Disable ICMP unreachable notifications on all external interfaces.

Step 1: The Arista router can be configured to filter out the ICMP Unreachable for (Type 3) code 0 (Network unreachable) IPv4 and IPv6 packets with the following command:

router(config)#ip icmp rate-limit-unreachable 0
router(config)#ipv6 icmp rate-limit-unreachable 0

Step 2: The Arista router can be configured to filter out the ICMP Unreachable for (Type 3) code 1 (Network unreachable) IPv4 and IPv6 packets with the following command:

router(config)#ip access-list BLK-ICMP-Unreachables
10 deny icmp any any host-unreachable
20 permit ip any any
!

Step 3: This would need to be applied on the egress interface (for example as in et1 below):

router(config)#interface ethernet1
no routerport
ip address 32.1.1.12/24
ip access-group BLK-ICMP-Unreachables out
!

See Also

https://dl.dod.cyber.mil/wp-content/uploads/stigs/zip/U_Arista_MLS_EOS_4-2x_Y23M02_STIG.zip

Item Details

References: CAT|II, CCI|CCI-002385, Rule-ID|SV-256032r882438_rule, STIG-ID|ARST-RT-000530, Vuln-ID|V-256032

Plugin: Arista

Control ID: 4863d57def8a3ba9b9669bc24e6fb93200660fa6504f93a9c8dbfcdcd122b56d