H3C Technologies H3C S10500 Series Switches - Manual (Page 28)

17
To do… Use the command… Remarks
Redistribute routes of the routing
protocol processes connecting the
MCE with the PE and the sites
respectively
import-route protocol [ process-id
| all-processes ] [ med med-value |
route-policy route-policy-name ] *
Required
By default, BGP does not
redistribute routes of any other
protocol.
• If the BGP process is for an
MCE and a site, the routes to be
redistributed must be from the
routing protocol process used
for advertising the routes of the
VPN between the MCE and PE.
• If the BGP process is for an
MCE and a PE, the routes to be
redistributed must be from the
routing protocol process used
for advertising the routes of the
VPN between the MCE and the
sites.
Configure a filtering policy to filter
the routes to be advertised
filter-policy { acl-number |
ip-prefix ip-prefix-name } export
[ direct | isis process-id | ospf
process-id | rip process-id | static ]
Optional
By default, BGP does not filter the
routes to be advertised.
Configure a filtering policy to filter
the received routes filter-policy { acl-number |
ip-prefix ip-prefix-name } import
Optional
By default, BGP does not filter the
received routes.
NOTE:
Normally, BGP checks routing loops by examining AS numbers. If eBGP is used between the MCE and
a site, when the MCE advertises its routing information with its AS number to the site and then receives
routing update information from the site, the route update message carries the AS number of the MCE,
making the MCE unable to receive this route update message. In this case, to enable the MCE to receive
route updates normally, configure the MCE to allow routing loops.
In standard BGP/OSPF route redistribution, when a route is redistributed into OSPF from BGP on the
MCE, the route’s original OSPF attribute cannot be restored, making the route unable to be
distinguished from routes redistributed from other domains. To distinguish routes of different OSPF
domains, you must enable a route to carry the OSPF domain ID when the route is redistributed from
OSPF into BGP on the peer PE. So, the domain ID of an OSPF process is carried in a route generated by
the process. When the OSPF route is redistributed into BGP, the domain ID is added to the BGP VPN
route and is transmitted over the network as the extended community attribute of BGP.
After configuring a BGP VPN instance, the BGP route exchange in the VPN instance is the same as the
common BGP’s. For more information about BGP configuration, see
Layer 3—IP Routing Configuration
Guide.