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Configuring eBGP between MCE and VPN site
To use eBGP for exchanging routing information between an MCE and VPN sites, you must configure a
BGP peer for each VPN instance on the MCE, and redistribute the IGP routes of each VPN instance on
the VPN sites.
If eBGP is used for route exchange, you also can configure filtering policies to filter the received routes
and the routes to be advertised.
1.
Configure the MCE
Follow these steps to configure the MCE:
To do…
Use the command…
Remarks
Enter system view
system-view
—
Enter BGP view
bgp
as-number
—
Enter BGP-VPN instance view
ipv4-family vpn-instance
vpn-instance-name
Required
Configure an eBGP peer
peer
{
group-name
|
ip-address
}
[
as-number
as-number
]
Allow routing loops—allow the
local AS number to appear in the
AS_PATH attribute of a received
route, and you can also configure
the maximum number of times that
such case is allowed to appear
peer
{
group-name
|
ip-address
}
allow-as-loop
[
number
]
Required
Use either command
Redistribute remote site routes
advertised by the PE
import-route
protocol
[
process-id
|
all-processes
] [
med
med-value
|
route-policy
route-policy-name
] *
Required
By default, no route redistribution is
configured.
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.
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. Thus, 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.
