Cisco Nexus 5600 Series Configuration Manual page 222

Guidelines and Limitations for ERSPAN
Scenario
ERSPAN has HIF Port Channel (with one or more
member HIF ports) as source with both Tx and Rx.
• The following scenarios are unaffected by any system limitations for ACL and SPAN session scaling:
• The following guidelines apply when configuring ERSPAN source sessions with ACLs:
Cisco Nexus 5600 Series NX-OS System Management Configuration Guide, Release 7.x
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◦ ERSPAN has single Switch Port as source with Tx only.
◦ ERSPAN has multiple Switch Ports as source with Tx only.
◦ ERSPAN has a Port Channel (with one or more member switch ports) as source with Tx only.
◦ ERSPAN has a single Host Interface (HIF) Port as source with Tx only.
◦ ERSPAN has multiple HIF Ports as source with Tx only.
◦ ERSPAN has a single Port HIF Channel (with one or more member HIF ports) as source with Tx
only.
◦ ERSPAN has a single Switch Port as source with Rx only.
◦ ERSPAN has multiple Switch Ports as source with Rx only.
◦ ERSPAN has a Port Channel (with one or more member switch ports) as source with Rx only.
◦ ERSPAN has a single HIF Port as source with with Rx only.
◦ ERSPAN has multiple HIF Ports as source with Rx only.
◦ ERSPAN has a HIF Port Channel (with one or more member HIF ports) as source with Rx only
◦ When you associate an ACL with an ERSPAN session, you must ensure that its size is not greater
than the calculations given in the table above. Otherwise the ERSPAN session fails and generate
a "TCAM resource unavailable" error. If the ACL has Layer 4 Operations and TCAM resource
expansion is enabled, you need to know the expected expanded size and you need to use the
expanded size to calculate the maximum ACL size.
◦ If you change the ACL that is attached to a ERSPAN session, the ACL size can exceed the maximum
ACL size allowed. In this scenario, the SPAN session continues to work with the modified ACL.
However, you should undo the ACEs added to the ACL to limit the size to maximum allowed ACL
size.
◦ If you add a ERSPAN session when one already exists, then to modify the first span session there
should be free TCAM entries of size equal to number of ACEs in the associated ACL (Assuming
that each ACE requires one TCAM entry. If it gets expanded, the expanded size should be
considered). Therefore, TCAM entries consumed by the second ERSPAN session should be
released.
◦ To replace a large ACL with another large ACL (which could cause the ERSPAN session to enter
a generic error state), you must first remove the existing filter access group (using the no filter
access-group current acl name command), and then configure the new filter access group (using
the filter access-group new acl name command).
Maximum ACL Size
Current Available TCAM Entries/4
Configuring ERSPAN
OL-31641-01