IP Multicast NAT Support

Version 33.6.1 adds IP Multicast NAT support, extending the existing basic source NAT capability to L3 IPv4 multicast traffic. The NAT router translates the source IP address in the IP header of each per-receiver multicast copy sent out on the egress VLAN.

Issue: Prior to this release, NAT translation was limited to IPv4 unicast traffic. Multicast sources using private IP addresses could not have their source addresses translated to registered public addresses when multicast streams crossed address domain boundaries.

Resolution: When IP Multicast NAT is enabled globally and a source-nat rule is configured, the NAT router performs per-copy source IP address translation for each replicated multicast packet. Translation is applied based on the source IP address, meaning a single SNAT rule covers all multicast groups originated by a given source host. Translation occurs only in the outbound direction; the destination multicast group address is never modified.

Key Capabilities:

• Global CLI knob to independently enable or disable IP multicast NAT (separate from unicast NAT)
• Per-copy source IP address translation for each multicast receiver copy
• Reuses existing source-nat rule type — no new rule type required
• Single SNAT rule applies to all multicast groups from the same source IP address
• Translation applies to outbound traffic only; inbound multicast destination address is not translated

Limitations:

• Supported only for L3 IPv4 multicast traffic; L2 multicast and IPv6 multicast are not supported
• Only the source-nat rule type is supported; napt and destination-napt rule types are not applicable
• Cannot be used concurrently with MACsec
• Not supported on stacking platforms
• ACL resources are consumed per source; scalability is bounded by available ACL hardware resources

Modified CLI Commands

Enable or disable IP multicast NAT globally:

enable ip nat multicast
disable ip nat multicast

The existing show ip nat command output now includes a Multicast NAT status line:

show ip nat

Sample configuration for two multicast sources:

configure ip nat add vlan in_vlan direction ingress
configure ip nat add vlan out_vlan direction egress

create ip nat rule snat1 type source-nat
configure ip nat rule snat1 egress vlan out_vlan
configure ip nat rule snat1 source 10.1.1.1 255.255.255.255 source-vr VR-Default newsource 20.1.1.100
enable ip nat rule snat1

create ip nat rule snat2 type source-nat
configure ip nat rule snat2 egress vlan out_vlan
configure ip nat rule snat2 source 10.1.1.2 255.255.255.255 source-vr VR-Default newsource 20.1.1.101
enable ip nat rule snat2

enable ip nat multicast
enable ip nat unicast