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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
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
]
Required
Use either command
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
]
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 will carry 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 from OSPF to 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 can specify
an OSPF domain ID for an OSPF process by using the
domain-id
command in OSPF view. The domain
ID of an OSPF process is carried in the routes generated by the process. When an OSPF route is
redistributed into BGP, the OSPF domain ID is included in the BGP VPN route and delivered as a BGP
extended community attribute.
