3Com 3C13636 Configuration Manual page 882

3Com Router 3000 Ethernet Family
Configuration Guide
VPN-target attribute, a BGP extension community attribute, controls advertisement of
VPN routing information.
It works on such principle:
When BGP redistributes a VPN route learned at CE, it associates a VPN-target
extension community attribute list with the route. Usually the list is the
VPN-instance output routing attribute list associated with CE.
VPN
import-extcommunity in VPN-target, defining the range of routes that are
acceptable and can be redistributed.
VPN instance modifies VPN-target attributes for the routes to be advertised,
according to the export-extcommunity in VPN-target.
Like RD, an extension community includes an ASN plus an arbitrary number or an IP
address plus an arbitrary number. There are two types of formats:
16-bit ASN: 32-bit user-defined number, for example, 101:3.
32-bit IP address: 16-bit user-defined number, for example, 192.168.122.15:1.
Perform the following configurations in the vpn-instance view.
Table 3-5 Configure vpn-target attribute for vpn-instance
Operation
Establish
extension community for
vpn-instance
Delete
vpn-target attribute from
the vpn-target attribute
list
By default, the value is both. In general all sites in a VPN can be interconnected, and
the import-extcommunity and export-extcommunity attributes are the same.
Up to 16 vpn-targets can be configured with a command, and up to 256 vpn-targets can
be configured for a VPN-INSTANCE.
5) Limit the maximum route number in a vpn-instance
This command is used to limit the maximum route number for a vpn-instance to avoid
too many routes at the import of PE router.
Perform the following configurations in the vpn-instance sub-mode.
Table 3-6 Limit the maximum route number for a vpn-instance
Limit the maximum route number for a
vpn-instance
instance defines
vpn-target
vpn-target
[ import-extcommunity | export-extcommunity |
both ]
the specified
undo
[ import-extcommunity | export-extcommunity |
both ]
Operation
3Com Corporation
Chapter 3 BGP/MPLS VPN Configuration
input routing attribute
Command
vpn-target
routing-table
{ warn-threshold | syslog-alert }
3-20
list according
vpn-target-extcommunity
vpn-target-extcommunity
Command
limit threshold-value
the