packet loss on summit 670 connected with LAG, MLAG ?

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Strange problem with packets loss. I have LAG on port 47-48 connected to 2 different switches with MLAG. I see problem only between pair:

src mac  f0:1f:af:d7:b5:37  and dst  mac  00:18:9d:08:c8:59 rest of traffic are ok. 

Summit sees in fdb table dst mac on port 47 but he sends via port 48 ( according to counters on port 47,48).. On next switch (uplink, also summit) i can't see any packets ( checked by port mirroring and ingress counters)

If i disable port 48 all works correct. If i change src mac address on server - all works also correct. 

There is  some well known bug in hashing in LAG/MLAG in v1531b4-patch1-18 ?

What has higher precedence when switch have to choose wich port use to send: entry in fdb or hash alghoritm ? 

 some outputs:

 Summit8.48 # show fdb 00:18:9d:08:c8:59

Mac Vlan Age Flags Port / Virtual Port List


00:18:9d:08:c8:59 vlan183(0183) 0041 d m 47


* Summit8.49 # debug hal show fdb | include 00:18:9d:08:c8:59

00:18:9d:08:c8:59 183 00001021 47 TRUE FALSE


* Summit8.65 # show policy trampek

Policies at Policy Server:

Policy: trampek

entry test4 {

if match all {

ethernet-source-address f0:1f:af:d7:b5:37;


then {

log ;

count trampek4 ;

permit ;



Number of clients bound to policy: 1

Client: acl bound once


Summit8.62 # show access-list counter ports 47 48 egress

Policy Name Vlan Name Port Direction

Counter Name Packet Count Byte Count


trampek * 47 egress

trampek4 0

trampek * 48 egress

trampek4 10


Image : ExtremeXOS version v1531b4-patch1-18

 enable sharing 47 grouping 47-48 algorithm address-based L3_L4 lacp


thanks for help,


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Posted 3 years ago

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Chad Smith, Alum

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Official Response

The EXOS software version you are running is susceptible to a known defect that can cause traffic forwarding problems:

PD4-4490184741:Traffic loss occurs on switches due to parity errors in L3 table.
With this issue only certain traffic flows will be affected (as you have described.  To confirm this issue a debug session with the GTAC would be required.

PD4-4490184741 was corrected in  However, the current recommended software version for the X670 platform is EXOS

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Chad Smith, Alum

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Official Response
I have created a GTAC Knowledge article that provides further information on these software defects: Traffic loss due to parity errors