08-11-2013 08:56 AM
All,
We are experiencing an issue with some virtual Kemp LB's in our environment where they are not functioning properly with regard to multicast, and their HA.
We came across a doc that seems to point to a possible solution:
https://supportforums.cisco.com/thread/2013429
I'm no multicast wizard, but one thing that's throwing me is this whole concept of specifying a querier within the VLAN. I am assuming that there has to be a layer 3 device in that VLAN (specified by the IP address of the querier) to perform this function?
Can someone explain the nuances regarding the querier?, or if anyone has had any similar issues in the UCS environment when dealing with muticast, I'd appreciate any information you could provide.
08-12-2013 07:24 AM
Hello James,
I hope that you are doing great.
According to our internal documentation referencing to the igmp snooping on FabricInterconnect, it is necessary to have deployed a multicast router.
Here there is part of the documentation.
In terms of Fabric failover, when you enable this on a UCS blade's vNIC, this really only affects unicast traffic and not multicast. This is because the unicast forwarding table is sync'd between the two FI's using CFS (Cisco Fabric Services), so after a failover occurs, the Interconnect can simply issue a gratuitous ARP (GARP) and traffic is virtually unaffected. In terms of multicast traffic, when a fabric failover event occurs the following happen:
As you can see, multicast convergence relys on the standard IGMP timers and during this period there could be a short loss of traffic.
There are a couple ways you can minimize (but not eliminate) traffic disruption
Hopefully, this information will help you.
Best Regards
Cristina Alvarado
Cisco Virtual Engineering - Partner Help
08-12-2013 10:04 AM
Christina,
Thank you for your time on this, but we are not having an issue with regard to FI failover, we are having an issue where the customers virtual Kemp Load Balancers are not communicating correctly when on different B series blades (when on the same blade, they communicate fine).
My issue with this configuration of the querier, is that the docs seem to suggest that you can specify a querier by IPv4 address even though there isn't an SVI or other layer 3 device that actually owns that IP.
Ultimately, I'd like to know what specifically is needed in the UCS environment in order for VM's that live on blades that use multicast to communicate to function properly.
Thank you,
James
09-13-2013 01:14 PM
You don't need a SVI interface to configure the Multicast Querier in the FI, you can use the IP address of UCS Manager for it.
09-13-2013 01:15 PM
You don't need a SVI interface to configure the Multicast Querier in the FI, you can use the IP address of UCS Manager for it.
09-13-2013 08:46 PM
All,
I was able to sort this out by utilizing the 'disable-loop-detection' command on the 1k (under the veth port profile) for the specific protocol that the virtual kemp load balancers were using. Just fyi to anyone else having this type of issue, you may need to check the type of protocol with a sniffer, as our server guys stated that the docs specified CARP, but wireshark showed VRRP, so when I first disabled loop detection for CARP, the LB's still weren't working, but when I disabled it for VRRP, it began working fine.
James
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