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it cannot ping peer device when the packet pass through S5720HI device.

Publication Date:  2017-10-29 Views:  484 Downloads:  0
Issue Description

Product: S5720HI Version: V200R009C00SPC500

Customer reported that it cannot ping peer device when the packet pass through S5720HI device.

 

Topology

#

interface GigabitEthernet0/0/2

 description sro-trunk-sro-sd-switch1

 set flow-stat interval 10

 port link-type trunk

 port trunk allow-pass vlan 60 101 201 268

 iplpm link loss-measure alarm enable

 iplpm link loss-measure enable

#

 

1) Use PC ping XXX website, if the PC connect other device or 5720HI, there will be some packet loss when the packet passes through the S5720HI.

2) Use PC ping XXX website, if the PC connect directly to the Router, PING is normal and there is no packet lost.

3) If the PC directly connected to all above equipment and ping other website like Sohu Yahoo, PING is normal, there will be no packet loss.

Customers suspect that there is some compatibility issue between our equipment and XXX website.

Handling Process

1, Check the physical link connection

Use the “display this interface” to check the physical interface, and found there is no packet dropped.

2, check the route table.

Use “display ip routing-table” to check the route table, and found both the route table and out interface are correct

3, Use ACL to do traffic statistics, to confirm whether the packet was sent by our device.

[HUAWEI] acl 3000

[HUAWEI-acl-adv-3000] rule 0 permit icmp source X.X.X.X 0 destination Y.Y.Y.Y 0 

[HUAWEI-acl-adv-3000] rule 5 permit icmp source Y.Y.Y.Y 0 destination X.X.X.X 0

[HUAWEI-acl-adv-3000] quit

[HUAWEI] traffic classifier c1

[HUAWEI-classifier-c1] if-match acl 3000

[HUAWEI-classifier-c1] quit

[HUAWEI] traffic behavior b1

[HUAWEI-behavior-b1] statistic enable

[HUAWEI-behavior-b1] quit

[HUAWEI] traffic policy p1

[HUAWEI-trafficpolicy-p1] classifier c1 behavior b1

[HUAWEI-trafficpolicy-p1] quit

[HUAWEI] interface gigabitethernet 0/0/2

[HUAWEI-GigabitEthernet0/0/2] traffic-policy p1 inbound

[HUAWEI-GigabitEthernet0/0/2] traffic-policy p1 outbound

 

[HUAWEI]display traffic policy statistics interface GigabitEthernet 0/0/2 inbound

[HUAWEI]display traffic policy statistics interface GigabitEthernet 0/0/2 outbound

 

We found that the packet has been sent out, but our device did not receive the respond packet.

4. Capture the packet sent by our device, we found that our device did not receive the respond packet when bit 0 in the Flags field is set to 1.

 

 

5. We found that customer enable the iplpm on the interface. By default, bit 0 in the Flags field is used as the color bit in device-level packet loss measurement (device and direct link).

Root Cause

iPCA can be used for device-level packet loss statistics. When this function is enabled, iPCA periodically sets and resets a certain color bit in service packet headers. This feature is used for direct connection equipment, and both device must be configured.

The iPCA feature has enabled on the S5720HI device, it cause that bit 0 in the Flags field packet will be set to 1 periodically

Solution

Since the peer does not support the iPCA function, delete the iPCA configuration directly. After the deletion, it is working fine.

END