Information Technology Reference
In-Depth Information
Example 10-39 shows the LFIB on ASBR1, where the outgoing label 22 is Lv2 and the
local label 22 is Lv3.
Example 10-39
LFIB on ASBR1
ASBR1#show tag forwarding
Local Outgoing Prefix Bytes tag Outgoing Next Hop
tag tag or VC or Tunnel Id switched interface
17 Pop tag 192.168.56.6/32 1770 Et1/0 192.168.56.6
18 Pop tag 192.168.23.0/24 0 Et0/0 192.168.35.3
19 17 192.168.100.2/32 0 Et0/0 192.168.35.3
20 Pop tag 192.168.100.3/32 0 Et0/0 192.168.35.3
22 22 65002:200:172.16.0.0/16 \
0 Et1/0 192.168.56.6
When the VPNv4 prefix is advertised to PE1, ASBR1 resets itself (192.168.100.5) as the
BGP next hop. This causes a new label stack to be created. Example 10-40 shows the label
stack on PE1 for the VPNv4 prefix 172.16.0.0. The label 22 is Lv3.
Example 10-40
Label Stack on PE1
PE1#show ip cef vrf VPNa 172.16.0.0
172.16.0.0/16, version 15, epoch 0, cached adjacency 192.168.23.3
0 packets, 0 bytes
tag information set
local tag: VPN-route-head
fast tag rewrite with Et1/0, 192.168.23.3, tags imposed: {18 22}
via 192.168.100.5, 0 dependencies, recursive
next hop 192.168.23.3, Ethernet1/0 via 192.168.100.5/32
valid cached adjacency
tag rewrite with Et1/0, 192.168.23.3, tags imposed: {18 22}
Deployment Considerations
This section focuses on various considerations in MPLS VPN deployment. Specifically, the
following subjects are discussed:
•
Scalability
•
Route target design examples
•
Convergence
Scalability
The subject of scalability is of special concern to MPLS VPN deployment, because VRF
significantly increases resource consumption. When you design an MPLS VPN, carefully
