Cisco ASA 5505 show arp is showing a "Not Vendor" MAC Address

[hcarmenates1]

Hello everyone

I am having some issues with a Cisco ASA 5505 connected to the Comcast Modem/Router (Cisco DPC3941B). Every week (once a week) the ASA loses its outbound connection and I am having to Power Cycle the ASA and the Comcast Router.

At this time it is working but when I run the "show arp"command it showes:

...

...

outside 50.244.xxx.yyyy f64b.2ab2.23eb

And when I do a MAC Lookup thta OUI (f64b2a) is not any vendor (not vendor)

In the Comcast Cisco Label in the back of the device it is the written MAC f44b2ab223e8 (it is f44b2a OUI)

OUI Look up for the MAC in Label showes correctly - CiscoSpv Cisco SPVTG

Why is the show arp showing me a bad (unrecognized vendor) MAC Address?

Why is the ASA getting this bad entry in its ARP Table?

I already had tried cleaning the arp and I have tried turning off and on both Comcast Modem and the ASA with the same results.

Can anyone help me?

Thank you

[Flavio Miranda]

Hello,

  About the Mac Address:

There are two kind of Mac Address: Universally administered addresses or locally administered addresses. 

 Universally Administered Address can be tracked to a vendor. Locally Administered Address can not.

Bellow the available Locally Administered Address range:

x2-xx-xx-xx-xx-xx
x6-xx-xx-xx-xx-xx
xA-xx-xx-xx-xx-xx
xE-xx-xx-xx-xx-x

In your case, your mac address falls on the second range. 

Now, why your Comcast Modem/Router has a Locally Administered Address is another question. One thing is true, someone put it there, maybe the Service Provider, Maybe the vendor. 

 You can dig on it thought.

-If I helped you somehow, please, rate it as useful.-