vrrp announcements flooding

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Hi experts,

I performed a tcp dump in a server of my current network and I'm getting lots of VRRP announcements in this vlan (where server belongs), This server is directly connected to the pair of Summit x460-48t where I have the VRRP configured.10.49.8.2 (Virtual IP .1) as Switch Master, behind this pair of Switches, I have another Extreme Switches with the same behavior and in the same vlan, where Switch Master 10.49.8.4 (Virtual IP.6)  First question is if this is a normal behavior and if It's possible to eliminate this multicast flooding?



The statistics below from the trace, I do not know if it's a normal rate time coming from the Vrrp  since now VRRP mcast is close to the 70% of traffic captured on this trace. :S

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Sergio Galvez

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Posted 3 years ago

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Bill Stritzinger, Alum

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Can you please post your VRRP configuration? Are the VRID's the same? Can you give a quick diagram of the network?

Bill
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Prashanth KG, Employee

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Hi Sergio,

As Bill stated, VRRP configuration and the topology could really help understand the network. 
To answer your questions in general, since VRRP advertisements are sent to well known multicast group address, the switch by default would be flooding this packet to all the ports in the VLAN irrespective of the IGMP snooping.

So, seeing these advertisements on the server could be expected. Regarding the rate at which these are received, please check the VRRP advertisement interval in the configuration of the switches. By default, they are at 1 second interval. If it is set to less than that in milliseconds or centiseconds, we may see many advertisements from the VRRP master within a second. 

Hope this helps! 
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Mike D, Alum

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Hello Sergio,



As discussed flooding is expected.   It's necessary for proper operation of vrrp and not something you will want to suppress.
Though 70%, the figure is a tiny tiny percentage of the available bandwidth.  Your network will never miss it.  You may come to appreciate the pace of this traffic as it signals normal and healthy default gateway operation.  

Making some assumptions about your configuration - master of each VIP should send an announcement once a second.  Clockwork.  I'd expect the packet rate to be 2 pps (see column 2), but 10.49.8.4 sends too many packets.  So yes, I think there's clear evidence of silliness afoot.  Some version related illness (column 8).
 
Regards,
Mike
  
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Sergio Galvez

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Hi guys,

Thanks for your replies, here is the topology


And I found the Configuration as follows:

Switch#1

create vrrp vlan EXT vrid 50
configure vrrp vlan EXT vrid 50 priority 200
configure vrrp vlan EXT vrid 50 add 10.49.8.6
enable vrrp vlan EXT vrid 50

Switch#2
create vrrp vlan EXT vrid 50
configure vrrp vlan EXT vrid 50 priority 100
configure vrrp vlan EXT vrid 50 add 10.49.8.6
enable vrrp vlan EXT vrid 50

Switch#3
create vrrp vlan EXT vrid 4
configure vrrp vlan EXT vrid 4 priority 200
configure vrrp vlan EXT vrid 4 version v2  // any impact if remove this?
configure vrrp vlan EXT vrid 4 add 10.49.8.1
enable vrrp vlan EXT vrid 4

Switch#4
create vrrp vlan EXT vrid 4
configure vrrp vlan EXT vrid 4 priority 100
configure vrrp vlan EXT vrid 4 add 10.49.8.1
enable vrrp vlan EXT vrid 4


AS you can see is not required special parameters and the Announcement Time as default is OK, There's no other request about the config/timers, just it need to be functional :)


Also be aware that this trace was taken with a low traffic rate, so It's supposed that is a normal behavior if we find just the v3 advertisements?


Thanks for your feedback guys


Regards

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Prashanth KG, Employee

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Hi Sergio,

Just curious to know about the SW versions for SW1 and SW2 ? SW2 is sending only the V2 advertisements.

We are seeing the VRRPv3 advertisements only from SW4. (10.49.8.4). which is expected if you are running 15.x version. 

In 15.x version, the VRRP version by default is v3-v2. This is for backward compatability of the versions. So, both v3 and v2 advertisements are seen. 

So, if you do not want to use the V3 advertisement, you could just configure the following command in the SW4. 

configure vrrp vlan EXT vrid 4 version v2. 

This command would make SW4 to advertise only version v2 messages. 

Apart from the other change, I think what you are seeing in the network looks expected. Even the wireshark indicates 1 second interval between the VRRP advertisements. 

10.49.8.2 @ 3.403 seconds
10.49.8.2 @ 4.403 seconds
10.49.8.2 @ 5.403 seconds.

Hope this helps!!
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Martin Flammia

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