Supported Platforms
Configuring Load Balancing on AMS Infrastructure
Configuring load balancing requires an aggregated Multiservices (AMS) system. AMS involves grouping several Multiservices PICs together. An AMS configuration eliminates the need for separate routers within a system. The primary benefit of having an AMS configuration is the ability to support load balancing of traffic across multiple services PICs.
 | Note: AMS is supported only on Mobility Gateway (MBG) with the MBG MS-DPC. AMS is not supported with JUNOS services like NAT, FW, IPsec, DAA, HCM on the current MS-DPC. |
Starting with Junos OS 11.4, high availability (HA) is supported on AMS infrastructure on all MX Series 3D Universal Edge routers. AMS has several benefits:
- Support for configuring behavior if a Multiservices PIC that is part of the AMS configuration fails
- Support for specifying hash keys for each service set in either direction
- Support for adding routes to individual PICs within the AMS system
Configuring AMS Infrastructure
AMS supports load balancing across multiple service sets. All ingress or egress traffic for a service set can be load balanced across different services PICs. To enable load balancing, you have to configure an aggregate interface with existing services interfaces.
To configure failure behavior in AMS, include the member-failure-options statement:
If a PIC fails, the traffic to the failed PIC can be configured to be redistributed by using the redistribute-all-traffic statement at the [edit interfaces interface-name load-balancing-options member-failure-options] hierarchy level. If the drop-member-traffic statement is used, all traffic to the failed PIC is dropped. Both options are mutually exclusive.
| Note: If member-failure-options is not explicitly configured, the default behavior is to drop member traffic with a rejoin timeout of 120 seconds. |
Only mams- interfaces (services interfaces that are part of AMS) can be aggregated. After an AMS interface has been configured, the constituent mams- interfaces cannot be individually configured. A mams- interface cannot be used as an rms interface. AMS supports only IPv4; inet6 family is not supported. It is not possible to configure addresses on an AMS interface. Network Address Translation (NAT) is the only application that runs on AMS infrastructure at this time.
| Note: Unit 0 on an AMS interface cannot be configured. |
To support multiple applications and different types of translation, AMS infrastructure supports configuring hashing for each service set. The hash keys can be configured separately for ingress and egress. The default configuration uses source IP, destination IP, and the protocol for hashing; incoming-interface for ingress and outgoing-interface for egress are also available.
Configuring High Availability
In an AMS system configured with high availability, a designated Multiservices PIC acts as a backup for other active PICs that are part of the AMS system. Presently, only N:1 backup for high availability is supported; only one PIC is available as backup for all other active PICs. High availability for load balancing is configured by adding the high-availability-options statement at the [edit interfaces interface-name load-balancing-options] hierarchy level.
To configure high availability, include the high-availability-options statement:
Load Balancing Network Address Translation Flows
Starting with Junos OS Release 11.4, Network Address Translation (NAT) has been programmed as a plug-in and is a function of load balancing and high availability. The plug-in runs on AMS infrastructure. All flows for translation are automatically distributed to different services PICs that are part of the AMS infrastructure. In case of failure of an active Multiservices PIC, the configured backup Multiservices PIC wiIl take over the NAT pool resources of the failed PIC. The hashing method selected depends on the type of NAT. Using NAT on AMS infrastructure has a few limitations:
- NAT flows to failed PICs cannot be restored.
- There is no support for IPv6 flows.
- Twice NAT is not supported for load balancing.
See Example: Configuring Static Source Translation on AMS Infrastructure for more details on configuring NAT flows for load balancing.
