Title

The RUCKUS ICX switch must enable Unidirectional Link Detection (UDLD) to protect against one-way connections. (Cat II impact)

Discussion

In topologies where fiber optic interconnections are used, physical misconnections can occur that allow a link to appear to be up when there is a mismatched set of transmit/receive pairs. When such a physical misconfiguration occurs, protocols such as STP can cause network instability. UDLD is a layer 2 protocol that can detect these physical misconfigurations by verifying that traffic is flowing bidirectionally between neighbors. Ports with UDLD enabled periodically transmit packets to neighbor devices. If the packets are not echoed back within a specific time frame, the link is flagged as unidirectional and the interface is shut down.

Check Content

Review configuration for UDLD configuration ("link keep-alive"). Router# show link-keepalive Total link-keepalive enabled ports: 4 Keepalive Retries: 3 Keepalive Interval: 1 Sec. Port Physical Link Logical Link State Link-vlan 1/1/1 up up FORWARDING 3 1/1/2 up up FORWARDING 1/1/3 down down DISABLED 1/1/4 up down DISABLED If UDLD is not configured to protect against one-way connections, this is a finding.

Fix Text

Configure the switch to enable UDLD to protect against one-way connections. 1. On a port for untagged control packets: Router(config)# link-keepalive ethernet 1/1/1 2. Optional trunk group: Router(config)# link-keepalive ethernet 1/1/1 ethernet 1/1/2 Note: To receive and send UDLD control packets tagged with a specific VLAN ID: Router(config)# link-keepalive ethernet 1/1/18 vlan 22

Additional Identifiers

Rule ID: SV-273687r1110990_rule

Vulnerability ID: V-273687

Group Title: SRG-NET-000512-L2S-000004

Expert Comments

CCIs tied to check.

Controls tied to check. These are derived from the CCIs shown above.