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ASA 5505 captures on same interface

jessica jestol
Level 1
Level 1

I replaced an archaic cisco router from 2003 with an ASA 5505. Currently, it only has one security level and one vlan. All ports are configured to use that inside interface with intra-interface. Basically just a switch. The reason behind this is long and convoluted but, please accept this was the only it could be done for now. The outside interface won't be added for 3 months. In the meantime, I've been trying to do some troubleshooting with packet captures and capturing on the inside interface gives me nothing even though there are several devices connected to the asa and I can connect to the devices via ssh. Is this just a shortcoming or am I missing something? If I connected two laptops on the inside interface, how can I capture traffic between the two?

3 Replies 3

johnd2310
Level 8
Level 8

Hi,

 

Are the laptops talking outside the inside network or are they talking to each other on the firewall? How are you running the capture? what happens when you run the capture  my_capture interface inside

 

Thanks

John

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talking to each other or talking to devices connected to a L2 switch connected to the ASA. All on the inside interface. The only traffic I see when I do a generic capture like that is my ssh traffic to the ASA.

Can give diagram for the same?
Any device connected to L2 switch on same vlan and same subnet never hit the gateway to communicate with each other. So example
Lap A with ip 1.1.1.1/24 want to talk to Lap B with ip 1.1.1.2/24. This two laptops are directly connected to a L2 switch and ASA is connected to that switch as well with ip 1.1.1.254/24 on inside interface. Both laptop has ASA inside ip as their gateway. In this scenario Lap A communication with Lap B never Hit ASA and vice versa as Lap A sees the destination network is in same subnet so it will arp for the Lap B and they will communicate directly. So ASA will never be part of this communication so no packet will be captured.

This is based on my understanding from the post. Please provide more information and diagram to understand the query better.

HTH
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