If Citrix ADC is connected to a switch/router via Fortville NIC (For example 10G port on MPX 8900), interface will show UP for a moment then go to Err-Disabled state. Running "show interface" command on ADC, you can find ADC Fortville NIC is in Err-Disabled State, along with TX Stall and Hang counts. Issue can be reproduced even if the NIC is bound to a channel. 

For example:

Interface 10/1 (10G Ethernet, SR, 10 Gbit) #9  Error-Disabled
        flags=0x4004110 <ENABLED, DOWN(PWR OFF), BOUND to LA/2, down, autoneg, 802.1q>
        MTU=1500, MAC=00:e0:ed:dd:ff:22, downtime 0h11m36s
        Requested: media AUTO, speed AUTO, duplex AUTO, fctl OFF,
                 throughput 0
        LLDP Mode: NONE,                 LR Priority: 1024

        RX: Pkts(469) Bytes(383025) Errs(0) Drops(469) Stalls(0)
        TX: Pkts(139) Bytes(5838) Errs(0) Drops(12) Stalls(38)
        NIC: InDisc(0) OutDisc(0) Fctls(0) Stalls(0) Hangs(25) Muted(0)
        Bandwidth thresholds are not set.
        Rx Ring: Configured size=2048, Actual size=512, Type: Elastic

Enable/Disable the interface can't recover, but reboot can bring UP state back. However, issue will happen again. 

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Current Workaround:
1. Disable LLDP on peer Switch/Router.
2. Reboot ADC to recover the error state. 

Upcoming Solution:
Citrix ADC Engineering team is working on qualifying newer versions of Fortville firmware from Intel, an ADC firmware upgrade will include the fix in the future and this article will be updated. 
 

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Problem Cause

This is caused by a NIC firmware compatibility issue with LLDP. Triggers are: 

• LLDP is enabled on peer router/switch, not matter LLDP configuration on ADC.
• NIC driver is Fortville.

For ADC platforms that is using Fortville NIC, please check: Fortville NICs firmware upgrade on Citrix ADC MPX appliances 

Note:
Possibility is not 100% when peer sending LLDP messages. There're some unknown triggers under Intel investigation. 

There is a known compatibility issue on Fortville NICs with LLDP, NIC goes into Err-disabled state. Disable LLDP on Switch/Router that cabling with ADC can help workaround this issue.