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Cisco Bug: CSCvs83434 - DHCPv6 does not work due to LDRA

Last Modified

Sep 01, 2020

Products (1)

  • Cisco Catalyst 4000 Series Switches

Known Affected Releases

15.2(6)E2

Description (partial)

Symptom:
DHCPv6 client is not able to get IPv6 address once LDRA server-facing policy is enabled on the uplink of switch.

"debug ipv6 dhcp-ldra" shows SOLICIT message received from the client and RELAY-FORWARD message generated by the switch, but the RELAY-FORWARD message is not put on the wire.

Example:
*Jan 28 06:51:56.504: DHCPv6 LDRA EVENT: [Gi5/1 Vlan 114] Received SOLICIT from FE80::277:8DFF:FE38:A16C to FF02::1:2.
*Jan 28 06:51:56.504: DHCPv6 LDRA EVENT: [Vlan 114] Sending RELAY-FORWARD from F
VANIR#E80::277:8DFF:FE38:A16C to FF02::1:2.

There are no RELAY-REPLY in the debug.
Packet capture on the uplink doesn't show any DHCPv6 packets relayed.

Conditions:
- DHCPv6 client is connected to an access switch which has dual/redundant uplinks:

Interface           Role Sts Cost      Prio.Nbr Type
------------------- ---- --- --------- -------- --------------------------------
Te1/1               Altn BLK 500       128.1    P2p  ### 2nd uplink blocked by STP
Te1/2               Root FWD 200       128.2    P2p ### 1st uplink 
Gi5/1               Desg FWD 4         128.513  P2p  ### Client port

- Client facing interface has a client-facing LDRA policy (either trusted or untrusted) 
- Uplinks have a server-facing LDRA policy

VANIR#sh ipv6 dhcp-ldra                                    
DHCPv6 LDRA is Enabled.
DHCPv6 LDRA policy: client-facing-disable
	Target: none

DHCPv6 LDRA policy: client-facing-trusted
	Target: Gi5/1 

DHCPv6 LDRA policy: client-facing-untrusted
	Target: none

DHCPv6 LDRA policy: server-facing
	Target: Te1/1 Te1/2
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