Information Technology Reference
In-Depth Information
Example 10-29 LFIB on ASBR2 (Continued)
20 16 192.168.100.4/32 5076 Et0/0 192.168.67.7
21 Pop tag 192.168.100.7/32 2349 Et0/0 192.168.67.7
22 19 192.168.100.2/32 4690 Et1/0 192.168.56.5
23 20 192.168.100.3/32 1755 Et1/0 192.168.56.5
On ASBR1, the incoming BGP label is swapped with an IGP label 17 (L2). In this case,
there is no outgoing BGP label. The LFIB is shown in Example 10-30. The IGP label 17 is
later popped by RR1 because of PHP (not shown). The end-to-end LSP from PE2 to PE1
is now complete.
Example 10-30 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 2280 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 43690 Et0/0 192.168.35.3
20 Pop tag 192.168.100.3/32 124651 Et0/0 192.168.35.3
21 20 192.168.100.4/32 2016 Et1/0 192.168.56.6
22 21 192.168.100.7/32 522 Et1/0 192.168.56.6
Remote Addresses Carried in iBGP with Labels
When the loopback addresses of RRs and PE devices in the remote AS are carried directly
in iBGP, you must enable the IPv4 label option on BGP sessions between RRs and their
clients (PEs and ASBRs). Figure 10-22 shows label distribution in such an environment.
Figure 10-22 Label Exchange with Multihop eBGP Between RRs Using iBGP with Labels
100:1:172.16.0.0/16
NH=PE1, RT=100:1
VPNv4 Label=Lv
100:1:172.16.0.0/16
NH=PE1, RT=100:1
VPNv4 Label=Lv
100:1:172.16.0.0/16
NH=PE1, RT=100:1
VPNv4 Label=Lv
192.168.100.2/32
BGP NH=ASBR2
BGP Label=L4
192.168.100.6/32
IGP NH=RR2
IGP Label=L6
192.168.100.2/32
BGP NH=ASBR2
BGP Label=L4
RR2
RR1
192.168.100.2/32
NH=PE1
IGP Label=L1
192.168.100.2/32
NH=RR1
IGP Label=L2
192.168.100.6/32
IGP NH=ASBR2
IGP Label=L5
192.168.100.2/32
NH=ASBR1
BGP Label=L3
ASBR2
PE1
ASBR1
PE2
AS 100
AS 200
 
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