The routed path for an RSVP-TE LSP can be described by a configured sequence of the LSRs and/or subnets traversed by the path. Each defined LSR or subnet represents an ERO subobject. Up to 64 subobjects can be added to each path name. LSRs and/or subnets can be either included or excluded.
configure mpls rsvp-te path path_name add ero {include} ipNetmask [strict|loose] {order number}
configure mpls rsvp-te path path_name add ero exclude ipNetmask {order number}
These commands add an IP address to the explicit route object (ERO) for the specified path name. The include keyword is optional and the default behavior is to define an ERO that must be included in the path. The exclude keyword allows a path to be created that must avoid certain subnets. This can be useful when defining redundant LSPs or paths that must avoid the path of other LSPs or paths.
The ipaddress keyword identifies an LSR using either a /32 address, which may represent an LSR router ID, loopback address, or direct router interface, or an IP prefix, which represents a directly connected subnet. Each IP address or prefix is included in the ERO as an IPv4 subobject.
For EROs that are configured to be included in the path calculation, if the IP address is specified as strict, the strict subobject must be topologically4 adjacent to the previous subobject as listed in the ERO. If the IP address is specified as loose, the loose subobject is not required to be topologically adjacent to the previous subobject as listed in the ERO. If omitted, the default subobject attribute is loose.
For EROs that are configured to be excluded in the path calculation, a given subnet is avoided if any address on that subnet is specified.
If the subobject matches a direct router interface or a directly attached subnet, the switch verifies that the path message is received on the matching router interface. The LSR path order is optionally specified using the order keyword. The order number parameter is an integer value from 1 to 65535. IP prefixes with a lower order number are sequenced before IP prefixes with a higher number. You can specify multiple addresses and assign them an order number. The order number determines the path that the LSP follows. Thus, the LSP follows the configured path of the IP prefix with the order value from low to high. If the order keyword is not specified, the number value for the LSR defaults to a value 100 higher than the current highest number value. For excluded nodes, the order is not important. Any excluded ERO will be always be avoided no matter where it is in the list of ERO objects.
If the list of IP prefixes added to the path does not reflect an actual path through the network topology, the path message is returned with an error from a downstream LSR and the LSP is not established.
The order of a configured subobject can not be changed. The ERO subobject must be deleted and re-added using a different order. If a subobject is added to or deleted from the ERO while the associated LSP is established, the path is torn down and is resignaled using the new ERO. Duplicate ERO subobjects are not allowed. Defining an ERO for the path is optional. If you do not configure an ERO, the path is signaled along the best CSPF calculated path and the ERO is not included in the path message. When the last subobject in the ERO of the path message is reached and the egress IP node of the path has not been reached, the remaining path to the egress node is signaled along the best CSPF calculated path. Specification of an ERO could lead to undesirable routed paths, so care should be taken when terminating the ERO routed-path definition prior to the configured path egress node.
To delete an RSVP-TE explicit route, use the following command:
configure mpls rsvp-te path path_name delete ero [all | ipNetmask | order number]
This command deletes an LSR or subnet from the ERO for the specified path name. The LSR is specified using the ipaddress, or order parameter. If an LSR is deleted from an ERO while the associated LSP is established, the path is torn down and is resignaled using a new ERO. Use the all keyword to delete the entire ERO from the path name. When there is no configured ERO, the path is no longer required to take an explicit routed path. The path is then signaled along the best CSPF calculated path and no ERO is included in the path message.
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