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Level 13

Need Help With Odd Networking Issue


2 ISP connected to barracuda link balancers behind Cisco ASA

We host multiple applications internally that are accessible from the outside. The two  we are seeing the most issues with are Webmail(call is and a  Child Support App (call it

Each application has 2 IP addresses 1 from each ISP

From outside of the network you are able to establish a connection  to one of the two, but never both*See note1 below.  So if you are able to access you will not be able to access ( and vice versa. A few people cant get to either.

From inside the network both services work fine.

All hosted on same Virtual environment,  IP addresses are within 5 of each other.

We can see the clients packets hitting the server, but when the server replies they never make it back to client.

Note1: When testing from Amsterdam using pingdom the test was successful to both

  • Opened tickets with both ISPs,
  • Rebooted ASA
  • Rebooted Link balancers
  • Rebooted Application Servers
  • Some of our applications are working for everyone on the outside.

I apologize that the above sounds like the rants of a crazy person!

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4 Replies

That's a weird one!

With the success of the pingdom tests, I think my first question would be 'what's different about the traffic from Amsterdam than traffic from US-based clients'?

Also, do you see anything interesting in the replies from the server - the traffic that never makes it back to the client? I assume you're peforming packet captures here.

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Thank you for your reply! Late Friday we actually resolved it.

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Don't leave me hanging, dude - what was the answer?

haha, i hate when people do that so i apologize. It was a issue with routing on the core switch. So a reboot resolved the issue, however we still do not know what caused the corruption.