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The SBC Core supports configuring up to 254 alternate media IP addresses using the parameter altMediaIpAddresses when configuring IP interfaces. Any combination of IPv4 and IPv6 is allowed and applies to all supported protocols (SIP, H.323, GW-GW).

A total of 4,096 IP Addresses are supported for SBC 5000 series and 8,192 IP Addresses are supported for SBC 7000, which is the system limit on IP addresses for each SBC variant.

The below table provides just a few examples of IP address/alternate IP address/alternate Media IP address combinations equaling 4,096 IP addresses.

Table : IP Address Distribution Examples

ExampleIP Address Combinations No.

Assign 256 IP addresses to each of a set of 16 IP interfaces

1 primary IP Addresses + 1 Alternate IP Address + 254 Alternate Media IP Addresses16

Assign 128  IP addresses to each of a set of 32 IP interfaces

1 Primary IP Address + 127 Alternate Media IP Addresses32

Assign a single primary IP address to each  of the 4,096 interfaces

1 Primary IP Address4,096

Most user configurations will not need 4,096 IP interfaces.

Alternate Media IPs are chosen based on Round Robin method (for example, the first call uses the primary IP and port, the second call uses the first configured alternate Media IP and port, the third call uses the second configured alternate Media IP, and so on). Each alternate Media IP must be unique across all interfaces in the same addressContext. However, the IPs may overlap between SIP, H.323 or Gateway signaling IP addresses in the same Address Context.

The following constraints apply:

  • An IPv4/IPv6 alternate media IP address is only allowed if a primary IPv4/IPv6 address exists.
  • An alternate media IP address must be in the same IP subnet as the primary media IP address (of the same IP version).
  • An alternate media IP address can only be deleted if the IP interface is in state disabled. However, it may be added while the IP interface is enabled and in-service.

The CLI command syntax to configure alternate media IP addresses is shown below. For details, refer to IP Interface Group - CLI.

% set addressContext <addressContext name> ipInterfaceGroup <interface group> ipInterface <interface> altMediaIpAddresses <IPv4/IPv6 address>