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RSVP Hello for Fast Reroute

Hi,

i am trying to set up TE tunnels with Fast Reroute protection. As i am using FastEthernet and GigabitEthernet links i need to use RSVP Hello for link or node failure detection.

I have a little problem understanding and properly configuring the rsvp hello feature. The topology looks as follows:

PE1 - P1 - PE2

  |                |

P3 ----------- P4

I am trying to set up fast reroute to  protect the connection PE1-P1-PE2 with backup path PE1-P3-P4-PE2. Both primary and backup tunnels are set up and working. I configure RSVP Hello on the link between PE1 and P1 with following commands on  PE1 and P1:

PE1#configure terminal

PE1(config)#interface Fastethernet 0/0

PE1(config-if)ip rsvp signalling hello

PE1(config-if)ip rsvp signalling hello refresh interval 50

P1#configure terminal

P1(config)#interface Fastethernet 0/0

P1(config-if)ip rsvp signalling hello

P1(config-if)ip rsvp signalling hello refresh interval 50

After issuing the sh ip rsvp hello instance detail command on PE1 i can see that the RSVP hello session is active:

Neighbor 195.10.3.1 (router ID: 3.3.3.3)  Source  195.10.3.254

    Type: Active    (sending requests)

    I/F:  FastEthernet0/0

    State:   Up        (Since: 2012 January Thursday 12 00:14:22 )

    Clients: Fast Reroute

    LSPs protecting: 1

    Missed acks: 4, IP DSCP: 0x30

    Refresh Interval (msec)

      Configured: 50

However on the P1 router the output shows different values:

Neighbor 195.10.3.254 (router ID: 33.33.33.33)  Source  195.10.3.1

    Type: Active    (sending requests)

    I/F:  FastEthernet0/0

    State:   Up        (Since: 2012 January Wednesday 11 23:43:18 )

    Clients: ReRoute

    LSPs protecting: 3

    Missed acks: 4, IP DSCP: 0x30

    Refresh Interval (msec)

      Configured: 2000

The configuration guide for IOS 12.2SR refers to active instances:

If a neighbor is unreachable when an LSP is ready  to be fast  rerouted, an active Hello instance is needed. Create an  active Hello  instance for each neighbor with at least one LSP in this  state.

and to passive instances:

Passive  Hello instances respond to Hello Request  messages (sending Ack  messages), but do not initiate Hello Request  messages and do not cause  LSPs to be fast rerouted.

At this point i am not sure if i configured the RSVP Hello properly. After shuting the interface FastEthernet 0/0 on P1 down i do get the backup tunnel active and rerouted, but the convergence time is too slow. I would expect the convergence time to be 4xRSVP Hello interval which is 4x50=200ms. However, the testing revealed the convergence time to be round 2,5 seconds. My goal is to get the convergence time under 300ms.

The question is, what is the actual difference between active and passive rsvp hello session? What does the Clients statement in the sh ip rsvp hello instance detail command mean and shoud i see the same interval on both ends of the link?

If you need any other specification, i will provide any other show command outputs necessary.

Thank you for any help or clarifiation.

Adrian

1 REPLY
Cisco Employee

RSVP Hello for Fast Reroute

Adrian,

Would it be possible to post the relevant tunnel configurations from your PE routers? From what you described, I am not sure if you want to achieve an MPLS path protection, MPLS link protection (NHOP) or MPLS node protection (NNHOP) here.

Best regards,

Peter

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