Users Guide

Synchronizing iSCSI Sessions Learned on VLT-Lags
with VLT-Peer
The following behavior occurs during synchronization of iSCSI sessions.
• If the iSCSI login request packet is received on a port belonging to a VLT lag, the information is synced to the VLT peer and the
connection is associated with this interface.
• Additional updates to connections (including aging updates) that are learnt on VLT lag members are synced to the peer.
• When receiving an iSCSI login request on a non-VLT interface followed by a response from a VLT interface, the session is not synced
since it is initially learnt on a non-VLT interface through the request packet.
• The peer that sees the login response packet generates a new connection log. If the login response packet uses the ICL path, it is seen
by both the peers, which in turn generate logs for this connection.
Monitoring iSCSI Traffic Flows
The switch snoops iSCSI session-establishment and termination packets by installing classifier rules that trap iSCSI protocol packets to the
CPU for examination.
Devices that initiate iSCSI sessions usually use well-known TCP ports 3260 or 860 to contact targets. When you enable iSCSI optimization,
by default the switch identifies IP packets to or from these ports as iSCSI traffic.
You can configure the switch to monitor traffic for additional port numbers or a combination of port number and target IP address, and
you can remove the well-known port numbers from monitoring.
Information Monitored in iSCSI Traffic Flows
iSCSI optimization examines the following data in packets and uses the data to track the session and create the classifier entries that
enable QoS treatment.
• Initiator’s IP Address
• Target’s IP Address
• ISID (Initiator defined session identifier)
• Initiator’s IQN (iSCSI qualified name)
• Target’s IQN
• Initiator’s TCP Port
• Target’s TCP Port
• Connection ID
• Aging
• Up Time
If no iSCSI traffic is detected for a session during a user-configurable aging period, the session data is cleared.
If more than 256 simultaneous sessions are logged continuously, the following message displays indicating the queue rate limit has been
reached:
%Z9500LC48:1 %ACL_AGENT-3-ISCSI_OPT_MAX_SESS_LIMIT_REACHED: Monitored iSCSI sessionsreached
maximum limit
NOTE
: If you are using EqualLogic or Compellent storage arrays, more than 256 simultaneous iSCSI sessions are possible.
However, iSCSI session monitoring is not capable of monitoring more than 256 simultaneous iSCSI sessions. If this number is
exceeded, sessions are not detected by the switch; but it does not affect forwarding. Dell Networking recommends that you
disable iSCSI session monitoring for EqualLogic and Compellent storage arrays or for installations with more than 256
simultaneous iSCSI sessions.
534 iSCSI Optimization