Cisco 6500 Multicast Error Messages

[John Pong]

We are encountering the error message below however upon checking Cisco's Bug ToolKit information, we cannot find our IOS version from the Known Affected Versions list. Any inputs would help.

CSCek26282 - MCAST-SP-STDBY-6-GC_LIMIT_EXCEEDED report on standby card

IOS Version - (s72033_rp-ADVENTERPRISEK9_WAN-M), Version 12.2(33)SXH8b

http://tools.cisco.com/Support/BugToolKit/search/getBugDetails.do?method=fetchBugDetails&bugId=CSCek26282

%MCAST-SPSTBY-6-GC_LIMIT_EXCEEDED: IGMP snooping was trying to allocate more Layer 2 entries than what allowed (15488)

%MCAST-SP-6-LTL_WATER_MARK:  Number of free LTL indices in the system has reached above the low threshold (400)

%MCAST-SP-6-LTL_LOW_WATER_MARK:  Number of free LTL indices in the system has reached below the low threshold (200)

%MCAST-SPSTBY-6-GC_LIMIT_EXCEEDED: IGMP snooping was trying to allocate more Layer 2 entries than what allowed (15488)

Thanks!

[rdirkse]

My log is flooding with:

Sep  5 00:37:47.491 UTC: %MCAST-SP-6-LTL_WATER_MARK:  Number of free LTL indices in the system has reached above the low threshold (400)

Sep  5 00:37:52.375 UTC: %MCAST-SP-6-LTL_LOW_WATER_MARK:  Number of free LTL indices in the system has reached below the low threshold (200)

(I don't get the GC_LIMIT_EXCEEDED messages)

Anyone able to explain what these mean?

Thanks You!!

Ralph

[InayathUlla Sharieff · Accepted solution]

Ralph,

%MCAST-SP-6-LTL_WATER_MARK:  Number of free LTL indices in the system has reached above the low threshold (400)

Indicates that you are using up the number of availble LTL indexs on the
box. LTLs are pointers that indicate which ports should receive a frame.
For mutlicast, LTLs are a dynamic, limited resource. If you run out of
LTLs, it's possible that the multicast traffic will flood within the
VLAN, similar to a broadcast.
Eg:

-->sh platform hardware capa multicast 

Multicast LTL Resources
  Usage:   30656 Total, 30448 Used

-->Switch multicast  LTL 

3 LTL indexes are used for for egress replication per mroute and two for ingress, per mroute. Also, L3 Routed interfaces require less LTL entries than L2 Switchports.
I would suggest you to open the tac case so that we do some more troubleshooting on this issue.

Most of the LTLs on the box are allocated due to source-only entries. Need to figure out whether these sources are legitimate or some kind of flooding on their network.


If legitimate and flooding on the VLAN is fine then you can use

    ip igmp snooping source-only-limit 

command to limit the number of source-only entries to avoid these messages.


Regarding the effect of these messages it that when the LTLs are exhausted the layer2 entries installed after hitting the threshold will start flooding.

HTH

Regards

Inayath

************PLZ RATE ALL USEFULL POSTS***********

[vsevolodbrol]

Hello,

Try this:

no ipv6 mld snooping 

Best regards.

[InayathUlla Sharieff]

I didnt investigate logs but looking at the bug I can say as of now that I dont see this under affected version of this bug:

http://tools.cisco.com/Support/BugToolKit/search/getBugDetails.do?method=fetchBugDetails&bugId=CSCek26282

And its been fixed in version 12.2(18.10.12)SX .

HTH

Regards

Inayath

.