Packet is not passing, if it is bigger than 72 byte ?

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Question :

I got Juniper router(M series), and we got GigabitEthernet service for ISP. We saw BGP dropped and no passing traffic since in this morning.
We are not able to ping ISP WAN IP which is directly connected. While we were troubleshooting, we found some weird situation. Only router allowed passing traffic with small size (less than 72byte). Physical cable and hardward wouldn’t be a problem(99%).

Anyone see those kinds of issue ?

What kinds of card on Cisco side ?
Have you checked any ACL on either routers ?

Yes, we took out all ACL on both side. Still saw same thing is happening, not passing traffic.
I don’t think it is telco line issue at all. Compared configuration, nothing special.
Hard to believe it might be bad card

 

Answer :

As you know, it would be everything.

My a cent tip would be trying loop testing.  From either router.

Example,   from cisco router.

Cisco_Router(config-if)#loopback internal
Loopback is a traffic-affecting operation
Cisco_Router(config-if)#ip address 1.1.1.1 255.255.255.252
Cisco_Router#

If you are able to ping yourself with bigger packet size, your hardware is okay.
However, if still same thing is happened, it would be bad GigabitEthernet card that you might need to replace.

Let me know what fix.

 

From user

Thank you ipBalance.com, I think it is hardware issue. Thru local loop testing still it passed small size packets only.
Once we moved a port to other router, it worked perfactly.
I suspected juniper side issue, but it turns out Cisco faulty card.

Anyway, it is kinds of weird issue.

Thanks again.