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MAC-Radius and VOIP functionality with LLDP-MED when connecting Avaya phones to EX series switches post 11.x.



Article ID: KB22894 KB Last Updated: 05 Mar 2017Version: 2.0
This article provides information about MAC-Radius and VOIP functionality with LLDP-MED, when connecting Avaya phones to EX series switches post 11.x.
When connecting Avaya phone to EX series switches using MAC-Radius and LLDP-MED, it has been noticed that the phone does not obtain an IP address from DHCP.
This article explains how Avaya phones behave, when connected to EX series switches configured for MAC-radius & LLDP-MED, when running Junos 11.X or later.

From the Avaya 4600 Series IP Telephone LAN Administrator Guide:

If the VLANTEST timer expires, and L2Q=1 (dot1q framing parameter), the telephone sets L2QVLAN=0 and transmits the DHCP messages with the default VLAN (0).

In 11.X, the phone is sending us DHCP discover messages with the VLAN tag set to the voice VLAN for 60 seconds (VLANTEST timer configuration default settings).

  1. The MAC-radius authentication is not yet complete and the phone reverts to sending DHCP discover messages with the default VLAN (vlan 0) tag.

  2. Now even after the authentication, the phone never reverts to using VLAN 10; even though LLDP-MED is advertising VLAN 10 as the voice VLAN.

  3. According to the guide, after VLANTEST expires, if an Avaya IP Telephone running R2.6 receives a non-zero L2QVLAN value, the telephone will release the IP address and send DHCPDISCOVER on that VLAN (correct behavior).

    Any other release requires a manual reset, before the telephone attempts to use a VLAN (advertized by LLDP-MED) on which VLANTEST has expired.

  4. If the VLANTEST interval is increased on the phone or is set to 0 / infinite, the phone successfully obtains an IP address from Voice VLAN.

  5. Root Cause:

    On Junos releases lesser than 11.X, events (a) and (b) happen. After this, the phone reverts to using VLAN 10 after a few seconds and is successfully assigned an IP address. The reason why it was working in earlier releases (10.4), is that the switch sends frequent LLDP power updates to the phone with different values in the power field.

    This was a bug which got fixed in 11.1 or later; however, this bug makes the LLDP PDU different each time.

    The Avaya phone has another peculiarity where regardless of firmware, even after VLANTEST timer expiry, if the LLDP frames or PDUs are different from prior ones, it will honor the VLAN-ID specified in the new frame and then send DHCP Discover with correct voice-VLAN ID.

    Note: When using Avaya Phones running R2.6, there is no issue for the phone getting authenticated and the DHCP address on switches running any release, as mentioned above.

Workaround options for the Avaya phone to work using EX-Series JUNOS 11.x versions and above:

  • Set VLANTEST timer to 0 (infinite) or increase the timer value on Avaya phones.

  • Use JUNOS 10.4.

  • Use Avaya FW R2.6.

  • Using dummy voice-VLAN ID on the switch and configuring the correct voice-VLAN ID on the radius server, which triggers change in the LLDP packet.
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