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Cisco Bug: CSCvi71861 - CTS IPv6 L2 DUG derrivation TCAM arrangement enhancement and increasing TSM pool for IPv6 DUG.

Last Modified

Sep 19, 2018

Products (1)

  • Cisco Catalyst 4500 Series Switches

Known Affected Releases


Description (partial)

We are using input ACL CAM to derive DUG for L2 IPv6 traffic. Currently we are writing entries to the CAM in the order in which we get binding entries. Since the entries are written in the order in which user adds it, user need to take care of the order also, ie user should add the highest prefix first. Else the packet will hit the first matching entry and that may be a generic one. Also if  ISE, SXP etc are used to get binding, user will not be able to do it in proper order.

Example: If a user configures 2 entries like below
Switch(config)#cts role-based sgt-map 1001::0/64 sgt 10
Switch(config)#cts role-based sgt-map 1001::2 sgt 20

Switch writes the first configured entry ie with 1001::0/64 in lower CAM index and then 1001::2.
When a packet comes with IP 1001::2 the lookup happens from lower to higher index and here
DUG derived will be 10, overthought we have a better match. 

To prevent this kind of situation we need to arrage TCAM entries in an order such that higher prefix
entries occupy the lower index in CAM.

This is the IPv6 continuation of enhancement CSCvg25491 done for IPv4.

Also current TSM pool for DUG have space only for 2048 entries. This is not enough for maximum number of IPv4 and IPv6 entries together. So need to increase the pool to such that we can have the  maximum number of IPv4 and IPv6 DGT entries together.

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