We have two DC's with 10G interconnection in between - these connections are run as L2 links - put into a set of nexus 5000 (the old nx5020) - acting access-switches - and uplinked to a set of nexus 7009 which act as L3 switch for us.
We have a cluster of vmware boxes in each site and are running MS windows 2008 machines with MS NLB for TerminalServices - in IGMP multicast mode - in VLAN 21.
Now I looked in the log of the nexus 7000 and found that the PIM DR is "flapping" between the two sites from time to time:
2013 Nov 25 22:50:58 ve-coresw-01 %PIM-5-DR_CHANGE: pim  DR change from 172.21.159.253 to 172.21.144.3 on interface Vlan21
2013 Nov 25 22:51:54 ve-coresw-01 %PIM-5-DR_CHANGE: pim  DR change from 172.21.144.3 to 172.21.159.253 on interface Vlan21
2013 Nov 25 23:26:07 ve-coresw-01 %PIM-5-DR_CHANGE: pim  DR change from 172.21.159.253 to 172.21.144.3 on interface Vlan21
2013 Nov 25 23:26:10 ve-coresw-01 %PIM-5-DR_CHANGE: pim  DR change from 172.21.144.3 to 172.21.159.253 on interface Vlan21
I am not that familiar with multicast but the basic concepts are there - in the vrf I have defined
ip pim ssm range 184.108.40.206/8
the vlan is defined as:
vlan configuration 21
layer-2 multicast lookup mac
under the SVI interface vlan 21 I have also defined - and there is a sample showning the nlb
vrf member DMZ_21
no ip redirects
ip address 172.21.144.3/20
ip pim sparse-mode
ip arp 172.21.149.19 0100.5E7F.9513
these flapping should only occur if the keep-alives between the two sites are missed 3 times
The uplinks to the nexus 5000 are defined as mrouters
ip igmp snooping mrouter interface port-channel5
ip igmp snooping mrouter interface port-channel16
SW5020-01# sh ip igmp snooping vl 21
IGMP Snooping information for vlan 21
IGMP snooping enabled
IGMP querier present, address: 172.21.144.3, version: 2, interface port-channel5 -> the DR on the nx7k
IGMPv3 Explicit tracking enabled
IGMPv2 Fast leave disabled
IGMPv1/v2 Report suppression enabled
IGMPv3 Report suppression disabled
Link Local Groups suppression enabled
Router port detection using PIM Hellos, IGMP Queries
Number of router-ports: 3
Number of groups: 3
VLAN vPC function enabled
Po10 Po15 Eth1/3 Eth1/11
Eth1/12 Eth1/13 Eth1/14 Eth1/15
Eth1/16 Eth1/17 Eth1/18 Eth1/19
Eth1/20 Eth1/25 Eth1/26 Eth1/27
Eth1/28 Eth1/29 Eth1/30 Eth1/31
Eth1/32 Po16 Po5
The link between the two sites - and boxes - is running error-free. As far as I can see there hasn't been any problems in that vlan since ??
If I look at f.ex spanning-tree the topology hast changed for long time in that vlan (2 weeks).
Could I harden the igmp multicast setup?
What is happening when a DR is changing? Will the multicast stop work or what happens?
As far as I understood the DR is the service which forwards the multicast traffic to the groups so if suddenly some re-negotiation occurs I would expect that the active traffic will be interrupted.
here the actual MS NLB clusters adresses:
SW5020-01# sh ip igmp snooping groups vl 21 Type: S - Static, D - Dynamic, R - Router port
Vlan Group Address Ver Type Port list 21 */* - R Po10 Po16 Po5 21 220.127.116.11 v1 D Eth1/14 Eth1/19 Eth1/32 21 18.104.22.168 v1 D Eth1/12 Eth1/15 Eth1/16 Eth1/26 Eth1/31 21 22.214.171.124 v2 D Po15 Eth1/11 Eth1/28 Eth1/29 SW5020-01#
To participate in this event, please use the button to ask your questions
This special event - formerly known as Ask the Expert- is open only to Cisco Customers and Partners.
Many pages in the Cisco Community are acce...
About this webinar
Cisco Application Centric Infrastructure (ACI) is designed API first, making it an automator’s, developer’s and programmer’s dream. When every aspect of a product is available via an API, there is no limit to the scale, robustnes...
Community Live - Application Centric Infrastructure: Introduction and Configuration Best Practices
This special event - formerly known as webcast- is open only to Cisco Customers and Partners.
Many pages in the Cisco Community are accessible o...