aggregate label problem

Answered Question
Feb 10th, 2009

on 12.4 11 T4 if i run the command for directly connected interface I got the aggregate label for that vrf. But if the ios is changed to 12.2 31 SB13 then I am getting no label. Which type of problem is it?

regards

shivlu jain

I have this problem too.
0 votes
Correct Answer by Harold Ritter about 7 years 11 months ago

Shivlu,

What you are referring to is the difference between "Aggregate", which forces an IP look-up and "Untagged", which forwards the packet directly towards the CE without an additional look-up.

In the following example, 192.168.27.0/24 is the Ethernet link between the PE and CE and it is therefore an aggregate and requires further processing before forwarding. On the other hand, 7.7.7.7/32 is received from the CE and packets destined to it are forwarded to the CE without any further look-up.

12.4(14)T

r2#sh mpls for

Local Outgoing Prefix Bytes tag Outgoing Next Hop

tag tag or VC or Tunnel Id switched interface

26 Untagged 7.7.7.7/32[V] 0 Et0/0 192.168.27.7

28 Aggregate 192.168.27.0/24[V] \

0

As you can see below, both these cases will show as "No Label" in the outgoing label field in the new mode (MFI).

12.3(31)SB13

r2#sh mpls for

Local Outgoing Prefix Bytes Label Outgoing Next Hop

Label Label or VC or Tunnel Id Switched interface

25 No Label 192.168.27.0/24[V] \

0 aggregate/red

28 No Label 7.7.7.7/32[V] 0 Et0/0 192.168.27.7

r2#

The fact that 192.168.27.0/24 needs an additional look-up is indicated by the "aggregate/" in the outgoing interface field rather than in the outgoing label field as it was the case before MFI.

Regards

  • 1
  • 2
  • 3
  • 4
  • 5
Overall Rating: 5 (2 ratings)
Loading.
Harold Ritter Tue, 02/10/2009 - 06:18

Shivlu,

This is not a problem. This behavior change was introduced in IOS via the new MPLS Forwarding Infrastructure (MFI). MFI was introduced to the 12.4T train in 12.4(20)T, hence you are seeing the old behavior in 12.4(11)T4. 12.2(31)SB13, on the other hand, has the MFI code.

If you examine the new behavior compared to the old, it make sense that the outgoing label show as "no label" as the traffic flowing towards the CE is unlabeled.

Regards

shivlu jain Tue, 02/10/2009 - 07:35

hi hritter

"Aggregate" and "No Label" having different functionality. Like aggregate means need to do the ip lookup and no labels means no need to do the ip lookup.

regards

shivlu jain

shivlu jain Tue, 02/10/2009 - 07:45

hritter

kindly provide any links for the same from where I can understand about MFI.

regards

shivlu jain

Correct Answer
Harold Ritter Tue, 02/10/2009 - 08:59

Shivlu,

What you are referring to is the difference between "Aggregate", which forces an IP look-up and "Untagged", which forwards the packet directly towards the CE without an additional look-up.

In the following example, 192.168.27.0/24 is the Ethernet link between the PE and CE and it is therefore an aggregate and requires further processing before forwarding. On the other hand, 7.7.7.7/32 is received from the CE and packets destined to it are forwarded to the CE without any further look-up.

12.4(14)T

r2#sh mpls for

Local Outgoing Prefix Bytes tag Outgoing Next Hop

tag tag or VC or Tunnel Id switched interface

26 Untagged 7.7.7.7/32[V] 0 Et0/0 192.168.27.7

28 Aggregate 192.168.27.0/24[V] \

0

As you can see below, both these cases will show as "No Label" in the outgoing label field in the new mode (MFI).

12.3(31)SB13

r2#sh mpls for

Local Outgoing Prefix Bytes Label Outgoing Next Hop

Label Label or VC or Tunnel Id Switched interface

25 No Label 192.168.27.0/24[V] \

0 aggregate/red

28 No Label 7.7.7.7/32[V] 0 Et0/0 192.168.27.7

r2#

The fact that 192.168.27.0/24 needs an additional look-up is indicated by the "aggregate/" in the outgoing interface field rather than in the outgoing label field as it was the case before MFI.

Regards

shivlu jain Tue, 02/10/2009 - 09:13

hritter

thanks for such the awesome explanation. If possible try to provide some link from where I can get more information about MFI.

regards

shivlu jain

Actions

This Discussion