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duplicated ping packets

duplicated ping packets

ywang
New Contributor

Hello,

Need some help for a very strange issue....


I currently have two VSP VOSS 7432CQ devices operating as vIST peers. They are connected via a link with ISIS SPBM running. And there are E XOS devices connect to vISP peers by SMLT. The management for the VSPs is assigned to context "mgmt" using VLAN 1008, and the EXOS devices also use VLAN 1008 for management purposes.

Recently, I introduced a new Juniper router into the network, connecting it behind one of the EXOS devices. The management of this Juniper router is also on VLAN 1008. Since this addition, I've encountered an issue where duplicate packets are generated when I initiate a ping from VSP1 to VSP2.

All the devices share the same subnet, specifically, a /24 subnet in vlan 1008:

VSP 1: 172.16.3.100
VSP 2: 172.16.3.101
EXOS: 172.16.3.103
Juniper: 172.16.3.113
When I attempt a ping from VSP 1 to VSP 2, I notice the occurrence of duplicate packets on VSP 1. Simultaneously, I can observe redirect responses from the Juniper router.

Further investigation reveals that the VSPs are sending ICMP packets twice as expected.

for exemple:
VSP-01:1#ping 172.16.3.101 count 10 mgmt
VSP-01:1#show mgmt ip icmp-statistics
================================================================================
Mgmt ICMP Statistics Information
================================================================================
InMsgs : 10
InErrors : 0
InCsumErrors : 0
InDestUnreachs : 0
InTimeExcds : 0
InParmProbs : 0
InSrcQuenchs : 0
InRedirects : 0
InEchos : 0
InEchoReps : 10 <----------receving 10 (but sometimes 20 while duplicate happens)
InTimestamps : 0
InTimestampReps : 0
InAddrMask : 0
InAddrMaskReps : 0
OutMsgs : 20
OutErrors : 0

OutDestUnreachs : 0
OutTimeExcds : 0
OutParmProbs : 0
OutSrcQuenchs : 0
OutRedirects : 0
OutEchos : 20 <-------------sending out 20 packets instead of 10
OutEchoReps : 0
OutTimestamps : 0
OutTimestampReps : 0
OutAddrMasks : 0
OutAddrMaskReps : 0
MsgInType0 : 10
MsgOutType8 : 20
---------------------------------------------------------- 

And i do captured on the juniper device the icmp packet from vsp1 to vsp2 (which is not a supposed behavior...) and the TTL decreased!


Best regards,

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GTM-P2G8KFN