Help Multicast Nexus 7000

[darrenriley5]

Hi,

We are currently migrating from Cisco 6500 switches to Nexus 7000 switches. I need replicate the following multicast configuration on the 6500 switches in the simplest way so Multicast is functioning on the Nexus 7000 switches.

Cisco 6500 configuration.

ip multicast-routing

interface Vlan8

description

ip address 10.128.46.2 255.255.240.0

ip helper-address 10.72.8.73

no ip redirects

ip pim dense-mode

ip route-cache flow

ip cgmp

standby 8 ip 10.128.32.1

standby 8 preempt

Please could some guidance be provided as to how we can enable multicast on the Nexus 7000 switches in the simplest form so this will continue operating.

Thanks

Darren

[csarto]

On NX-OS PIM dense-mode is not supported.

You need to migrate to PIM-Sparse-Mode, using the concept of PIM Rendezvous Points

For a brief introduction to Multicast Concept:

www.ciscolivevirtual.com BRKMPL-1261 - IP Multicast – Concepts, Design and Troubleshooting

Also

http://docwiki.cisco.com/wiki/Cisco_NX-OS/IOS_Multicast_Comparison

Just a brief config conversion the configuration on N7K (using auto-rp):

feature pim

feature interface-vlan

feature dhcp ! for DHCP-Relay / Helper Address

feature hsrp

service dhcp

ip dhcp relay

interface Vlan8

ip address 10.128.46.2 255.255.240.0

no ip redirects

ip pim sparse-mode ! enable PIM Sparse-Mode on interface

ip dhcp relay address 10.72.8.73

hsrp 8

ip 10.128.32.1

preempt

int loopback 100

description interface used for RP Address

ip add

ip pim sparse-mode ! enable PIM Sparse-Mode on interface

ip pim auto-rp rp-candidate loopback100 group-list 224.0.0.0/4

ip pim auto-rp mapping-agent loopback100

ip pim auto-rp forward listen

The "ip pim auto-rp forward listen" must be configured also on others N7k in your Multicast domain.

[darrenriley5]

Hi,

Thanks very much for your reply this could be a life saver. Our access switches which are combination of Cisco4507RE and Cisco 3750 switches connect to the Nexus switches via layer 2 trunks. Do we need to consider any multicasdt configuration on these. Currently there isn't any.

Many Thanks

Darren 

[csarto]

If the 4507RE and the 3750 are configured as Layer 3 switching you need to configure ip multicast routing also on them with ip pim sparse-mode under layer 3 interfaces (SVI or Routed interfaces). Otherwise igmp snooping is already active and you don't need any further configuration.

[darrenriley5]

Hi,

Just one final question. Am I ok to configure a secondary RP on my secondary Nexus? Am I correct in thinking  the system elects the device with the highest mapping-agent IP address?

Thanks

int loopback 100

description interface used for RP Address

ip add

ip pim sparse-mode ! enable PIM Sparse-Mode on interface

ip pim auto-rp rp-candidate loopback100 group-list 224.0.0.0/4

ip pim auto-rp mapping-agent loopback100

ip pim auto-rp forward listen

[csarto]

The highest candidate RP address is elected as RP for each group or range advertised.

Anyway I suggest to configure two (or more) Nexus 7k devices with the "PIM Anycast-RP" feature.

You can configure the Loopback100 on both devices with the same IP (f.i. 1.1.1.1 on N7k-1 and 1.1.1.1 on N7k-2), this is the RP address then the two devices communicate each other using another loopback IP .

In this manner you get fast convergence when a PIM Rendezvous Point (RP) router fails.

For further information rfc4610 - Anycast-RP using Protocol Independent Multicast (PIM) http://www.ietf.org/rfc/rfc4610.txt