SR OS supports multiple Layer 3 router instances. These instances have their own IP addressing spaces and parameters. Router instances are isolated from each other.
The following are the different types of router instances in SR OS:
Base
All SR OS routers have the Base router instance: the system created default router instance used to forward user IP traffic among router line card ports. Router interfaces (that is, network interfaces configured under configure router [Base]) and IES services and interfaces exist in the Base router instance. The Base router instance is identified in SNMP as vRtrType = baseRouter (1) and has a vRtrID of 1.
VPRN instances
Another type of router instance is the set of operator configured VPRN services. Each VPRN service has a unique router instance. For more information about VPRN services and their associated router instances, see the 7450 ESS, 7750 SR, 7950 XRS, and VSR Layer 3 Services Guide: IES and VPRN. VPRN router instances are identified in SNMP as vRtrType = vprn (2), and the vRtrID is dynamically allocated.
Special system router instances
SR OS routers also support the following special router instances:
management
The management router instance is a system created router instance that is used for management of the router. The management router instance is bound to CPM/CCM ports A/1 and B/1. This is a CPM router instance which cannot be renamed or deleted by an operator. The management router instance is identified in SNMP as vRtrType = vr(3), and the vRtrID is 4095.
vpls-management
The vpls-management router instance is used for management of VPLS services. It is identified in SNMP as vRtrType = vr(3), and the vRtrID is 4094.
User created CPM router instances
User created CPM router instances are user defined router instances that are mainly used with Ethernet ports on the CPM/CCM cards: CPM router instances only use CPM/CCM Ethernet ports as interfaces. CPM router instances have a user-defined name and are the only types of non-VPRN router instances that can be created by the user. User created CPM router instances are identified in SNMP as vRtrType = vr(3), and the vRtrID is dynamically allocated.
Some management protocols can use either the base routing instance (in-band) or the management routing instance (out-of-band). A listing of these protocols can be found in the CPM Filter: Protocols and Ports section of the 7450 ESS, 7750 SR, 7950 XRS, and VSR System Management Guide. Unless otherwise stated in the detailed description of the protocol, when the server or client for the protocol is reachable via the management routing instance, those protocol messages use the management interface for the protocol communication.
If BOF is set up with autoconfiguration and the DHCP server provides a general default route such as 0.0.0.0/0, with some protocols (like PCEP, TACACS+, RADIUS, and LDAP), Authentication, Authorization, Accounting (AAA) always prefers OOB over in-band connectivity. This is because these protocols prefer to use the OOB management port first. If a matching route is not found, in-band is attempted. The static route provided by DHCP must be properly set to ensure the correct route preference is made by these protocols.