Explain VRID conflicts and how to identify them.

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Instructions

What is a VRID (Virtual Router ID) Conflict?
Conflicts in VRID are messages logged when a packet has same source MAC Address as our vmac (virtual MAC) which indicates a network loop in topology.

When facing an issue with VRID conflicts, you will receive something along the lines of this is the log:

• Conflict in vrid x on interface LA/x vlan x bridge_group -x from MAC xx:xx:xx:xx:xx:xx IP x.x.x.x

You can retrieve the logs from the nslog directory at /var/nslog/, by running the following command in shell mode:

• nsconmsg -K newnslog -s disptime=1 -d consmsg | more

 

• Retrieve the following Data - This will allow you to identify all the configuration related to your VRID(s):

1. ADC interfaces configuration - https://developer-docs.netscaler.com/en-us/adc-command-reference-int/current-release/network/interface.html
2. ARP table of the ADC - https://developer-docs.netscaler.com/en-us/adc-command-reference-int/current-release/network/arp.html
3. VRID configuration - https://developer-docs.netscaler.com/en-us/adc-command-reference-int/current-release/network/vrID.html#show-vrid

 

• You may check for increments in the following counters, by executing the boldened commands in shell mode on CLI, :

1. VRID counters - /var/nslog/ -  nsconmsg -K newnslog -g arp_err_vrid_conflicts -s disptime=1 -d current | more
2. Duplicate ARP - /var/nslog/ -  nsconmsg -K newnslog -d current -g  arp_err_dup_pkts -s disptime=1 | more

Explain how to identify VRID conflicts With the data gathered using the steps provided, you can validate when there is a VRID conflict. What happens is that the ADC sends VRID packets (ARPs) advertising its own VRID configuration, these are broadcast packets with Source MAC = VMAC that the VRID has configured and source IP of the ADC, these packets are the ones that the ADC receives due a network error, caused by any device in the network that is routing this Broadcast packet back to the ADC. When the ADC receives this packet with a source MAC and IP owned by itself it generate the conflict log. In short is not a problem in the ADC is the network path causing this log error.

NetScaler Appliances in Active-Active Mode Using VRRP
 - https://docs.netscaler.com/en-us/citrix-adc/current-release/networking/interfaces/active-active-mode-using-vrrp.html
ADC interfaces configuration - https://developer-docs.netscaler.com/en-us/adc-command-reference-int/current-release/network/interface.html
ARP table of the ADC - https://developer-docs.netscaler.com/en-us/adc-command-reference-int/current-release/network/arp.html
VRID configuration - https://developer-docs.netscaler.com/en-us/adc-command-reference-int/current-release/network/vrID.html#show-vrid