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[EX] Duplicated DHCPv6 packets are seen between DHCPv6 Relay and Server

  [KB35035] Show Article Properties


Summary:

DHCPv6 packets will be duplicated on legacy EX switch platforms if they are sitting in between DHCPv6 relay and server devices. There should be no service impact, though it may unnecessarily consume device resource.

Symptoms:

DHCPv6 packets are being duplicated by EX4550 switches if it's been deployed in between DHCPv6 relay and server.

Topology:

 DHCPv6 Clients --- DHCPv6 Relay Agent (ae0) --- (ae2) EX4550 --- DHCPv6 Server

 
Results of 'monitor traffic interface ae2' on EX4550:
16:48:02.801085 Out
        Juniper PCAP Flags [Ext], PCAP Extension(s) total length 22
          Device Media Type Extension TLV #3, length 1, value: Ethernet (1)
          Logical Interface Encapsulation Extension TLV #6, length 1, value: Ethernet (14)
          Device Interface Index Extension TLV #1, length 2, value: 33536
          Logical Interface Index Extension TLV #4, length 4, value: 80
          Logical Unit Number Extension TLV #5, length 4, value: 4010
        -----original packet-----
        88:a2:5e:e4:f7:45 > 00:01:5c:85:b1:e7, ethertype 802.1Q (0x8100), length 355: vlan 4010, p 0, ethertype IPv6, (hlim 62, next-header: UDP (17),  length: 297) fd00:2578:172:101::bcc:1a.dhcpv6-server > fd00:0:d321:101::2.dhcpv6-server: [udp sum ok] dhcp6 Relay-reply
16:48:02.811862 Out
        Juniper PCAP Flags [Ext], PCAP Extension(s) total length 22
          Device Media Type Extension TLV #3, length 1, value: Ethernet (1)
          Logical Interface Encapsulation Extension TLV #6, length 1, value: Ethernet (14)
          Device Interface Index Extension TLV #1, length 2, value: 33536
          Logical Interface Index Extension TLV #4, length 4, value: 80
          Logical Unit Number Extension TLV #5, length 4, value: 4010
        -----original packet-----
        88:a2:5e:e4:f7:45 > 00:01:5c:85:b1:e7, ethertype 802.1Q (0x8100), length 355: vlan 4010, p 0, ethertype IPv6, (hlim 62, next-header: UDP (17),  length: 297) fd00:2578:172:101::bcc:1a.dhcpv6-server > fd00:0:d321:101::2.dhcpv6-server: [udp sum ok] dhcp6 Relay-reply

There are two DHCPv6 Relay-reply packets which are exactly the same.

Packet captures on switch port connecting DHCPv6 server:

Solution:

This issue is planned to be fixed in the upcoming Junos version. The versions will be added here once they are released.

Refer to PR1426377 - The DHCPv6 packets are getting mirrored by the EX switch

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