Subscriber Routed Redundancy Protocol (Srrp) - Alcatel-Lucent 7750 SR Manual

VPRN Features

Subscriber Routed Redundancy Protocol (SRRP)

Subscriber Routed Redundancy Protocol (SRRP) is closely tied to the multi-chassis
synchronization protocol used to synchronize information between redundant nodes. An MCS
peer must be configured and operational when subscriber hosts have a redundant connection to
two nodes. Subscriber hosts are identified by the ingress SAP, the hosts IP and MAC addresses.
Once a host is identified on one node, the MCS peering is used to inform the other node that the
host exists and conveys the dynamic DHCP lease state information of the host. MCS creates a
common association between the virtual ports (SAPs) shared by a subscriber. This association is
configured at the MCS peering level by defining a tag for a port and range of SAPs. The same tag
is defined on the other nodes peering context for another port (does not need to be the same port-
ID) with the same SAP range. In this manner, a subscriber host and Dot1Q tag sent across the
peering with the appropriate tag will be mapped to the redundant SAP on the other node.
Once SRRP is active on the group IP interface, the SRRP instance will attempt to communicate
through in-band (over the group IP interfaces SAPs) and out-of-band (over the group IP interfaces
redundant IP interface) messages to a remote router. If the remote router is also running SRRP
with the same SRRP instance ID, one router will enter a master state while the other router will
enter a backup state. Since both routers are sharing a common SRRP gateway MAC address that is
used for the SRRP gateway IP addresses and for proxy ARP functions, either node may act as the
default gateway for the attached subscriber hosts.
For proper operation, each subscriber subnet associated with the SRRP instance must have a gw-
address defined. The SRRP instance cannot be activated (no shutdown) unless each subscriber
subnet associated with the group IP interface has an SRRP gateway IP address. Once the SRRP
instance is activated, new subscriber subnets cannot be added without a corresponding SRRP
gateway IP address.
subscriber hosts associated with the group IP interface.
SRRP instances are created in the disabled state (shutdown). To activate SRRP the no shutdown
command in the SRRP context must be executed.
Before activating an SRRP instance on a group IP interface, the following actions are required:
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Table 22 describes how the SRRP instance state is used to manage access to
Add SRRP gateway IP addresses to all subscriber subnets associated with the group IP
interface, including subnets on subscriber IP interfaces associated as retail routing
contexts (at least one subnet must be on the subscriber IP interface containing the group IP
interface and its SRRP instance).
Create a redundant IP interface and associate it with the SRRP instances group IP
interface for shunting traffic to the remote router when master.
Specify the group IP interface SAP used for SRRP advertisement and Information
messaging.
7750 SR OS Services Guide