Label Distribution Protocol
400
MPLS Guide
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3HE 18686 AAAB TQZZA
Figure 26 Non-VPN mLDP with Recursive Opaque for Inter-AS
As shown in Figure 26, the leaf is in AS3s where the AS3 intermediate nodes do not
have ROOT-1 in their RTM. The leaf has S1 installed in the RTM via BGP. All ASBRs
are acting as next-hop-self in the BGP domain. The leaf resolving S1 via BGP will
generate an mLDP FEC with recursive opaque, represented as:
Leaf FEC: <Root=ASBR-3, opaque-value=<Root=Root-1, <opaque-value =
S1,G1>>>
This FEC will be routed through the AS3 Core to ASBR-3.
At ASBR-3, the FEC will be changed to:
ASBR-3 FEC: <Root=ASBR-1, opaque-value=<Root=Root-1, <opaque-value =
S1,G1>>>
This FEC will be routed from ASBR-3 to ASBR-1. ASBR-1 is colocated in the same
AS as ROOT-1. Therefore, ASBR-1 does not need a FEC with a recursive opaque
value.
ASBR-1 FEC: <Root=Root-1, <opaque-value =S1,G1>>
This process allows all multicast services to work over inter-AS networks.
sw1299
PE-2
(LEAF)
10.0.0.8
SAR Core AS3 SAR Core AS1
IGP, iBGP, mLDP
Host
Source
Join S1, G1
PIM Join
(S1, G1)
BGP update:
Prefix: Source, NH ASBR-1, Label X
RT Ext Com: XX
VRF RT IMP Ext Com ASBT-1:0
Source AS Ext Com: 2:0
LDP Fec: Root 10.0.0.21
Opaque <Root 10.0.0.14,
Opaque <S1, G1>>
LDP Fec: Root 10.0.0.2
Opaque <Root 10.0.0.14,
Opaque <S1, G1>>
LDP Fec:
Root 10.0.0.14
Opaque <S1, G1>
BGP update:
Prefix: Source, NH ASBR-3, Label Y
RT Ext Com: XX
VRF RT IMP Ext Com ASBT-3:0
Source AS Ext Com: 2:0
BGP update:
Prefix: Source, NH Root-1, Label Z
RT Ext Com: XX
VRF RT IMP Ext Com Root-1:0
Source AS Ext Com: 2:0
PIM Join
(S1, G1)
S1, G1
10.60.3.2, 192.0.2.60
IGP, iBGP, mLDP
eBGP, mLDP
ASBR-3
10.0.0.21
ASBR-1
10.0.0.2
PE-1
(ROOT-1)
10.0.0.14
Note: Note: AS3 intermediate nodes are not BGP-capable because they do not have
ROOT-1 in their RTM.