Information Technology Reference
In-Depth Information
In addition to the BGP prefixes, ASBR2 is also part of the OSPF domain in AS 200. It
distributes an IGP label, Implicit-Null, to RR2. Example 10-58 shows the LFIB on RR2
for 192.168.100.6 (ASBR2), where PHP occurs.
Example 10-58
LFIB on RR2
RR2#show tag forwarding
Local Outgoing Prefix Bytes tag Outgoing Next Hop
tag tag or VC or Tunnel Id switched interface
16 Pop tag 192.168.100.4/32 10898 Et1/0 192.168.47.4
17 Pop tag 192.168.56.0/24 2642 Et0/0 192.168.67.6
18 Pop tag 192.168.100.6/32 6672 Et0/0 192.168.67.6
Similarly, RR2 assigns an IGP label (18) to reach ASBR2 and distributes the binding to
PE2. Example 10-59 shows the LFIB on PE2.
Example 10-59
LFIB on PE2
PE2#show tag forwarding
Local Outgoing Prefix Bytes tag Outgoing Next Hop
tag tag or VC or Tunnel Id switched interface
16 Pop tag 192.168.100.7/32 0 Et1/0 192.168.47.7
18 Pop tag 192.168.67.0/24 0 Et1/0 192.168.47.7
19 17 192.168.56.0/24 0 Et1/0 192.168.47.7
20 18 192.168.100.6/32 0 Et1/0 192.168.47.7
Example 10-60 shows the label stack for the VPNv4 prefix 172.16.0.0 on PE2. The top
label, 18, is used to reach ASBR2 via RR2 (192.168.47.7); the middle label, 24, is used to
reach PE1 via ASBR2; and the bottom label, 24, is used to reach VPNa via PE1.
Example 10-60
Label Stack on PE2
PE2#show ip cef vrf VPNa 172.16.0.0
172.16.0.0/16, version 16, epoch 0, cached adjacency 192.168.47.7
0 packets, 0 bytes
tag information set
local tag: VPN-route-head
fast tag rewrite with Et1/0, 192.168.47.7, tags imposed: {18 24 24}
via 192.168.100.2, 0 dependencies, recursive
next hop 192.168.47.7, Ethernet1/0 via 192.168.100.2/32
valid cached adjacency
tag rewrite with Et1/0, 192.168.47.7, tags imposed: {18 24 24}
