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Configuring inter-AS option C
Configuring the PEs
You need to establish ordinary iBGP peer relationships between PEs and ASBR PEs in an AS and
MP-eBGP peer relationships between PEs of different ASs.
The PEs and ASBR PEs in an AS must be able to exchange labeled IPv4 routes.
To configure a PE for inter-AS option C:
To do…
Use the command…
Remarks
Enter system view
system-view
—
Enter BGP view
bgp
as-number
—
Configure the ASBR PE in the same
AS as the iBGP peer
peer
{
group-name
|
ip-address
}
as-number
as-number
Required
Enable the PE to exchange labeled
IPv4 routes with the ASBR PE in the
same AS
peer
{
group-name
|
ip-address
}
label-route-capability
Required
By default, the switch does not
advertise labeled routes to the IPv4
peer or peer group.
Configure the PE of another AS as
the eBGP peer
peer
{
group-name
|
ip-address
}
as-number
as-number
Required
Enter BGP-VPNv4 subaddress
family view
ipv4-family vpnv4
—
Enable the PE to exchange BGP
VPNv4 routing information with the
eBGP peer
peer
{
group-name
|
ip-address
}
enable
Required
Configure the PE not to change the
next hop of a route when
advertising it to the eBGP peer
peer
{
group-name
|
ip-address
}
next-hop-invariable
Optional
Required only when RRs are used
to advertise VPNv4 routes, where
the next hop of a route advertised
between RRs cannot be changed.
Configuring the ASBR PEs
In the inter-AS option C solution, an inter-AS LSP is required, and the routes advertised between the
relevant PEs and ASBRs must carry MPLS label information.
An ASBR-PE establishes common iBGP peer relationships with PEs in the same AS, and a common eBGP
peer relationship with the peer ASBR PE. All of them exchange labeled IPv4 routes.
NOTE:
On an ASBR-PE, do not configure the
peer ebgp-max-hop
command. Otherwise, the MPLS tunnel cannot
be established.
The public routes carrying MPLS labels are advertised through MP-BGP. According to RFC 3107
“Carrying Label Information in BGP-4”, the label mapping information for a particular route is
piggybacked in the same BGP update message that is used to distribute the route itself. This capability
is implemented through BGP extended attributes and requires that the BGP peers can handle labeled
IPv4 routes.
