Alcatel Unleashed

Hi all,

We have MPLS between two sites.
I see the BFD session as down but ospf is up.

how can I fix this issue?

Regards
Mike

Hi Mike,

Can send some config and show captures. Is bfd tied to the ospf?

Cheers

Sent from my C6833 using Tapatalk

For security purpose I can not send you config.
yes bfd is tied to ospf.

Is there any command I can run on 7750 or 6850 switch?

Regards
Mike

show router bfd session src <ip-address> detail
admin display-config | match bfd context all

Sanitise the output to remove anything you don't want to share on a public forum.

BFD bound to OSPF but is BFD enabled on the interfaces? You should see an error when you configure it this way.

If you are using CPM filters and deny all without matching BFD then you may need to match it there. BFD uses UDP 3784.

Warning: Making a mistake with your CPM filters can bring your network down!! Consult with your architecture or vendor support team and lab test before making changes.

which src ip address I should choose?
also bfd is enabled on the interface it was working fine till yesterday.
also bfd timer on the 7750 shows 1000

What is the src-ip for? A filter? The show command:
For a filter: If you are using a particular subnet across all your links a simplified catch-all will do. For example each link uses a /31 from 192.0.2.0/24 then your filter using src-ip 192.0.2.0/24 will match /24 and longer.
For the show command use your local IP as the source. Needs to match a local interface.

What type of line card is it on? If it worked and now doesn't then its likely a resource problem or something across the router has changed as opposed to a config problem. IOM3, for example, can handle 500pps of BFD traffic

As an example if you have bfd 100 rx 100 mu 10 then this one session per protocol is using 10 of the pps (490 pps remaining).

Local side example:
config int to_b
port 1/1/1
address 192.0.2.1/24
bfd 100 receive 100 multiplier 10
config router ospf area 0 int to_b bfd-enable

Far side:
configure interface to_a
port 1/1/1
address 192.0.2.2/24
bfd 100 receive 100 multiplier 10
config router ospf area 0 int to_a bfd-enable


Do that 50 times across the line card and your pps is used up and no more sessions can form. You can verify the amount of sessions using show router bfd session summary

Verify the exact session with show router bfd session src 192.0.2.1 detail of course replacing 192.0.2.1 with whatever your link local IP is.

Note BFD hellos are either generated by the card or the cpm depending on how frequently they transmit. This will be hardware dependant. For example I think anything below 100ms requires the CPM to play its part.

mike18 wrote:which src ip address I should choose?
also bfd is enabled on the interface it was working fine till yesterday.
also bfd timer on the 7750 shows 1000

If it was working fine until yesterday, then check the configs to see if there was a change.

Rick