OSPF Flapping in Exchange Mode / Network Interface Also Flapping - SAR 7705

[hbaloi]

Dears,

Can any one help on this. I have 3 SAR´s connected by two links in each direction as the topology bellow , but suddenly im facing flapping on the interfaces on the Router R1, and OSPF not stable . The physical is clean ... the log´s is shown :


"BFD: Local Discriminator 1902 BFD session to node 10.1.16.69 is down due to nbrSignalDown "
"BFD: Local Discriminator 1872 BFD session to node 10.1.16.65 is down due to nbrSignalDown "
"BFD: Local Discriminator 1872 BFD session to node 10.1.16.70 is down due to nbrSignalDown "
"Log file cf3:\act\act0806-20170216-150721.xml.gz on compact flash cf3 has been rolled over"


R3 ( 10.1.16.23 ) -------------------------------- R1 (10.1.16.25 ).......................... R2( 10.1.16.24 )



*A:R01>config>router# info
----------------------------------------------
#--------------------------------------------------
echo "IP Configuration"
#--------------------------------------------------
interface "To_R2"
address 10.1.16.18/30
port 1/1/8:45
qos 2
bfd 100 receive 100 multiplier 3
exit
interface "To_R2_2Link"
address 10.1.16.66/30
port 1/1/8:450
qos 2
bfd 100 receive 100 multiplier 3
exit
interface "To_R3"
address 10.1.16.14/30
port 1/1/8:35
qos 2
bfd 100 receive 100 multiplier 3
exit
interface "To_R3_2Link"
address 10.1.16.70/30
port 1/1/8:350
qos 2
bfd 100 receive 100 multiplier 3
exit
interface "system"
address 10.1.16.25/32
exit
autonomous-system 65000
ecmp 4


OSPF :

echo "OSPFv2 Configuration"
#--------------------------------------------------
ospf
traffic-engineering
export "static_to_ospf"
area 0.0.0.0
interface "system"
exit
interface "To_R1"
interface-type point-to-point
mtu 1572
metric 105
bfd-enable
exit
interface "To_R1_2Link"
interface-type point-to-point
bfd-enable
exit
interface "To_R3"
interface-type point-to-point
bfd-enable
exit
interface "To_R3_2Link"
interface-type point-to-point
bfd-enable
exit
exit
exit

[Eagleman]

HI,
I have gone through your configs, i can't see anything wrong other than unequal MTU values. You either remove it at where configured or add to where it wasn't configured in your configuration below.

nterface "To_R1"
interface-type point-to-point
mtu 1572 >>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>
metric 105
bfd-enable
exit
interface "To_R1_2Link"
interface-type point-to-point
NONE HERE>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>
bfd-enable
exit
interface "To_R3"
interface-type point-to-point
bfd-enable
NONE HERE>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>
exit
interface "To_R3_2Link"
interface-type point-to-point
NONE HERE>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>
bfd-enable

I hope you can update us with the outcome?.

[hbaloi]

Dear Eagle,

I will try to use your recomendations , and monitor .

Thank u .

Regards

[hbaloi]

Hello,

I did the changes , but interfaces still flapping :

26267 2017/02/28 13:38:20.92 CAT MAJOR: VRTR #2015 Base 10.1.16.69
"BFD: Local Discriminator 6503 BFD session to node 10.1.16.69 is up"

26266 2017/02/28 13:37:58.84 CAT MAJOR: VRTR #2012 Base 10.1.16.69
"BFD: Local Discriminator 6502 BFD session to node 10.1.16.69 is down due to nbrSignalDown "


Regards

[Rickdatech]

What does your research tell you is the reason why ospf gets stuck in exchange (cisco exstart) mode?
The most common is a MTU mismatch in the ospf interface config what are other reasons?

Have you checked those things?