Ping failed after configuring the URPF

Created: Sep 26, 2019 07:07:31Latest reply: Sep 27, 2019 08:37:32 157 10 0 0
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Pinging is successful before the urpf configuration, but failed after configuring the urpf on the access interface. The only changed configuration is the additional urpf checking. What is the potential reason, coule you guys help me?


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Featured Answers
chenhui
Admin Created Sep 27, 2019 08:36:52 Helpful(0) Helpful(0)

Posted by user_3445655 at 2019-09-27 08:36Yes, will that be the reason?

Yes, I think that is the reason. URPF wouldn’t check the default route by default. If you want the default route to be checked during the URPF inspection, additional configuration is required, please try to configure ip urpf allow default-route under the interface view, and check whether the pinging could work.
By the way, it’s strongly recommended NOT to allow the default route checking, because it will make the URPF meaningless.
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chenhui
chenhui Admin Created Sep 26, 2019 07:08:05 Helpful(0) Helpful(0)

Did you configure the URPF inspection with loose mode or strict mode?
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user_3445655
user_3445655 Created Sep 26, 2019 07:37:23 Helpful(0) Helpful(0)

Posted by chenhui at 2019-09-26 07:08 Did you configure the URPF inspection with loose mode or strict mode?
I tried both, no matter loose mode or strict mode, pinging is failure.
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chenhui
chenhui Admin Created Sep 26, 2019 07:37:39 Helpful(0) Helpful(0)

Posted by user_3445655 at 2019-09-26 07:37 I tried both, no matter loose mode or strict mode, pinging is failure.
Do the packets come from the out interface which the route towards to? Will you please verify that?
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user_3445655
user_3445655 Created Sep 26, 2019 09:38:26 Helpful(0) Helpful(0)

Posted by chenhui at 2019-09-26 07:37 Do the packets come from the out interface which the route towards to? Will you please verify that ...
port mirroring and packet capture result indicates the result is positive.
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chenhui
chenhui Admin Created Sep 26, 2019 09:38:51 Helpful(0) Helpful(0)

Posted by user_3445655 at 2019-09-26 09:38 port mirroring and packet capture result indicates the result is positive.
well, can you show us the corresponding routes?
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user_3445655
user_3445655 Created Sep 27, 2019 08:35:38 Helpful(0) Helpful(0)

Posted by chenhui at 2019-09-26 09:38 well, can you show us the corresponding routes?
sorry for the late.

Destination/Mask Proto Pre Cost Flags NextHop Interface

0.0.0.0/0 Static 60 0 RD 182.33.74.5 GigabitEthernet 0/0/0
10.133.10.0/28 Direct 0 0 D 10.133.10.5 GigabitEthernet 0/0/1
10.133.10.5/32 Direct 0 0 D 127.0.0.1 GigabitEthernet 0/0/1
10.133.20.0/24 O_ASE 150 1 D 10.133.10.6 GigabitEthernet0/0/1
10.133.20.1/32 OSPF 10 1 D 10.133.10.6 GigabitEthernet0/0/1
10.137.0.0/24 O_ASE 150 1 D 10.133.10.6 GigabitEthernet0/0/1
10.137.0.2/32 OSPF 10 1 D 10.133.10.6 GigabitEthernet0/0/1
127.0.0.0/8 Direct 0 0 D 127.0.0.1 InLoopBack0
127.0.0.1/32 Direct 0 0 D 127.0.0.1 InLoopBack0
x.x.74.0/27 Direct 0 0 D 182.33.74.7 GigabitEthernet0/0/0
x.x.74.7/32 Direct 0 0 D 127.0.0.1 GigabitEthernet0/0/0
192.168.194.0/24 O_ASE 150 1 D 10.133.10.6 GigabitEthernet0/0/1
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chenhui
chenhui Admin Created Sep 27, 2019 08:36:11 Helpful(0) Helpful(0)

Posted by user_3445655 at 2019-09-27 08:35 sorry for the late.Destination/Mask Proto Pre Cost Flags NextHop Interface ...
Did the traffic forwarded using the default routes?
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user_3445655
user_3445655 Created Sep 27, 2019 08:36:37 Helpful(0) Helpful(0)

Posted by chenhui at 2019-09-27 08:36 Did the traffic forwarded using the default routes?
Yes, will that be the reason?
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chenhui
chenhui Admin Created Sep 27, 2019 08:36:52 Helpful(0) Helpful(0)

Posted by user_3445655 at 2019-09-27 08:36Yes, will that be the reason?

Yes, I think that is the reason. URPF wouldn’t check the default route by default. If you want the default route to be checked during the URPF inspection, additional configuration is required, please try to configure ip urpf allow default-route under the interface view, and check whether the pinging could work.
By the way, it’s strongly recommended NOT to allow the default route checking, because it will make the URPF meaningless.
  • x
  • convention:

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