Discovering MAC addresses for Switch ports

Hello and thanks for looking at my question,
My company has inherited a network which has some very poor documentation. We really have no clue, nor does the customer, what machines are connected to what switch ports.
My co-worker and I were discussing the best way to find this out with the least amount of effort, but can't agree on a single solution. Any recommendations would be greatly appreciated.
Thanks.
Sincerely,
Brent

Brent,
After you do the 'sho arp' and now have MAC to IP translation, do a 'sho mac-address table' to show MAC to port translation. Save both tables to an Excel spreadsheet and tie them together. You should be able to come up with a good cross reference table (depending upon your Excel skills).
This also gives you a switch-by-switch breakout. It's also a very helpful troubleshooting method to find rouge devices and shut down a port (for instance).
Hope this is helpful.
Jim

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Many thanks for the swift response. However, there is no WAN MAC address on the box or on the device anywhere. I even used magnifying glass to find one .
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ARP table not populating mac address for previously reachable IP address

Router has been online and working fine with one BGP neighbor for almost 2 years and no downtime. 2 weeks ago, added a 2nd BGP peer. Everything worked fine for 2 weeks, then all of a sudden yesterday the 2nd BGP peer is disconnected and does not come back. ISP checks and sees everything looks fine on their end. We cannot even ping each other now.
Upon investigation, the ARP table is not even populating the MAC address for the BGP peer IP anymore (same local subnet). Stays "incomplete" in the table no matter what we do, including clearing arp table, changing IP address, etc.
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End up rebooting the router and lo-and-behold, everything is working normally again. 2nd BGP peer peers up instantly.
I should also mention that the 1st BGP peer worked flawlessly throughout, taking all the Internet load and having no issues throughout.
Also, the FE ports for the 2nd BGP peer are on an HWIC FE card plugged into the router. The 1st BGP peer is plugged into the built-in GE interface. 2901 running: c2900-universalk9-mz.SPA.151-4.M4.bin
Lastly, no router resource issues, no error messages, no logs. Just the BGP peer disconnecting.
I have never, in 20 years working with Cisco routers seen something like this before. This is the most fundamental aspect of IP and Ethernet that was not working.
Has anyone ever seen this behavior before??
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version 15.1
service timestamps debug datetime msec localtime show-timezone
service timestamps log datetime msec localtime show-timezone
service password-encryption
service internal
service sequence-numbers
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aaa authentication login TAUTHEN local group tacacs+ enable
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aaa authorization exec LAUTHOR local if-authenticated
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match access-group name Customer-VPNs
class-map match-any media
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class-map match-any signaling
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fair-queue
policy-map queue
class signaling
bandwidth percent 5
class media
priority percent 50
class Customer-Voice
priority percent 40
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interface GigabitEthernet0/0
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speed auto
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interface FastEthernet0/0/0
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ip address 1.1.1.1 255.255.255.252
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ip flow egress
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ip access-list standard SNMP_SOURCES
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ip prefix-list L3-DEFGW seq 5 permit 0.0.0.0/0
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ip prefix-list COLO-LPREF-OUT seq 5 permit 1.2.3.0/24
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When you were checking the ARP table was there an entry for Fast0/0/0?
HTH
Rick

How many mac-addresses a single port can store ?

How many mac-addresses a single port can store ?
And also what is the max limit for mac-addresses on a switch ?
Regards,
Chandu

Hi,
I don't think there is a limit per port.
The limit is the max number of entries in the CAM table so if for example the CAM table limit is 8000 and you already got 7200 entries you can have the 800 enties on different ports or on one port.
Regards
Alain
Don't forget to rate helpful posts.

I need to change the MAC Address for Airport on MacBook

I have a specific need to change my son's Airport MAC address as his school requires the use of USB network cards that aren't compatible with MACs. These cards are needed because the school's router uses MAC address filtering.
Before we upgraded his Mac to Snow Leopard, we were able to change the MAC address to the MAC address of the useless dongal the school supplied. We basically created an AppleScript program that ran the "sudo ifconfig en1 ether xx:xx:xx:xx:xx:xx" and all was good.
This command no longer works for changing the MAC address. We tried it as root user as well and by typing it into the terminal window as root. After running the command, we can run "ifconfig en1" and it does display the new mac address but when we turn the airport on and try to connect, it just hangs and won't connect.
Our other non-Snow Leopard still works fine after running the commands so I'm guessing Apple disabled this functionality. It's hardly a security issue by being able to change your mac addres.
Is there a new way to accomplish this? I've searched everywhere.
Thanks!

Would an easier solution be to provide the school's IT admin with your mac address and have it added? If they can add a block of mac addresses for the usb dongles, they can add more for machines that cannot use the dongle.
Also: "It's hardly a security issue by being able to change your mac address."
While it may not be a security issue for your machine, it is a security for the school network who is using mac address filtering as hopefully only one part of their wireless security.
That being said, have you read this?
http://osxdaily.com/2008/01/17/how-to-spoof-your-mac-address-in-mac-os-x/

How do I find the Mac address for my 8900?

I have a wireless network and can't connect to it at all. I have looked and typed in Blackberries search engine and came up with nothing, only answers are about a MAC computer, not what I am looking for.
I have to add the Mac address to the wireless network in order to get past the firewall and this is not working for me, any ideas.
Thank you,
Animal
Raising teenagers is like trying to nail
jell-O to a tree!

Found it,
Overview
To find the Media Access Control (MAC) address of a Wi-Fi® enabled BlackBerry smartphone, complete the following steps:
Click Options.
Click Status.
The WLAN MAC field displays the MAC address for the BlackBerry smartphone.
Raising teenagers is like trying to nail
jell-O to a tree!

IP-4-ZERO_ADDR: Zero MAC address for ip in ARP cache

Could someone hlep me with this log message: IP-4-ZERO_ADDR: Zero MAC address for <ip> in ARP cache
It just started appearing in our Cisco 10012 CMTS, and all of the documentation is very vague as to what it is and how to fix it. I'm hoping someone else has seen the message and can help clarify it's meaning. Thanks in advance!

Your not the only one with these logs mess :
Jan 20 13:05:10: %IP-4-ZERO_ADDR: Zero MAC address for 10.100.xxx.69 in ARP cache
Jan 20 13:30:02: %IP-4-ZERO_ADDR: Zero MAC address for 10.100.xxx.69 in ARP cache
I thing the reason is that someone has a worm or something ping-flooding/scanning the network, check your arp table for incompletes.
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Martin
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I am afraid I didn't get the clear picture of the issue mentioned in the post. Could you please elaborate a little bit? If you connect a device/computer wired and then later you connect it wirelessly. It is obvious that you would get to see two different MAC addresses for the same device, one for the LAN adaptor and other one for WLAN adaptor. If that is what you are referring to?
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On the bottom label it should list the MAC address.
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Pretty pictures no info.. think kid's book.
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Settings/General/About/WiFi Address.

MAC Address for iPAD

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How do you find the phone's mac address for Droid RAZR Maxx HD?

how do you find the phone's mac address for Droid RAZR Maxx HD?

Ann154 wrote:
WalrusM wrote:
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Motorolas list them under About Phone > Status.
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MAC address for HP PRO CP1525NW

I want to enforce MAC filtering in my router.The OS is win7 home pro 64 bit.
How do I find the MAC address for my CP1525nw printer? It is not on the label, and the router reports only the name of the printer.
This question was solved.
View Solution.

First, MAC filtering is not a security measure because it is so easily defeated. Read more here: http://blogs.zdnet.com/Ou/?p=43
If you want to continue, print a self test from the front of the printer: Reports > Config Report. It will be listed as the Hardware address.
Say thanks by clicking "Kudos" "thumbs up" in the post that helped you.
I am employed by HP

"failed to get MAC address for machine"

here is the jist of things.
installed leopard and have it pimped out to my personal specs. I like where everything is and how things are working. No issues. just so you know, i only use WIFI for internet, i share with the guys upstairs. In order to get wifi on my machine, i use a USB dongle. works great no issues with it ever, well until i physically broke it. No big deal. So i replaced it with another one, different drivers/chipset worked.. And since i installed leopard i only backed it up once with TM, i dont care for daily/hrly backups, weekly is fine for me. Now after 2 weeks and a new usb network card. TM gives me an error. i click on the little red i and it says "the backup volume could not be found" so googled and searched the forums not much help, so i tried and formated my ext drive repaired and click on TM again, same error. In the error log in console, right after i turn on TM i get this error, "failed to get MAC address for machine" then 180 secs later, TM fails. again, and again.
Can anyone tell me where i can find what MAC address its looking for??? ethernet has never been plugged in to my machine ever. its only been online via USB wifi. Im really lost here, i dont know what i can do.. im sure if i try another drive ill get the same error. please help if you can.. much appriciated.
Jamie

yeah i get a 'failed to get mac address' message too. what's weird is that it seems that leopard 'broke' my ethernet (there was no mac address, couldn't connect to the internet through ethernet after a clean install), and then 10.5.2 'fixed' it. for some reason, i have an 'ethernet 2' heading in system preferences that works correctly and has a mac address and everything, while the regular 'ethernet' tab doesn't work at all. however, i still get this time machine error. i don't understand why time machine is so incredibly fickle. sorry, i'm really of no help to anyone, other than adding another voice to the frustration.

WES610N - only one MAC address for all connected devices

Hi! I use a WES610N 4-port WLAN bridge to connect my audio and video devices (Pioneer AV receiver, Samsung TV set and a WD Live TV box) to my E4200 router upstairs. This works fine and the WLAN connection works stable and fast. There's a Synology 212j NAS running DM 3.2 connected to my E4200 router. On this NAS a DLNA/UPnP media server is running to stream audio and video from the NAS to my Receiver, to my TV set and to the WD Live TV box. Audio and video is ok but i also want to send photos from the NAS direct to the TV and WD Live. To see the photos in the correct solution i have to configure a DLNA profile on the media server for each DLNA client which connects to the media server. I have to configute this based on the device name, IP address and MAC address shown in the clinet list of the media server. So far so good - and here's my problem: Every device connected to the WES610N is seen with the same MAC address - the one of the WES610 - by the media server. This confuses the server and it's not possible to assign a DLNA profile to each of the devices (TV, Receiver, WD box) because the IP - MAC pairing always changes when one of the devices sends data packets to the media server. So the assigned profile configuration gets lost and switches back to standard DLNA profile and photos can not be displayed correct by the devices. So what i would need is that every device connected to the WES610N is seen by the media server by it's on MAC address. Is there a solution or are there plans to implement this in future firmware versions? Thx, BR Christian

You can try the following combination of settings :-
A] With the help of Cisco Connect Software (if at all you have installed the router with the help of this software)
1] Open the software and go to the option which says "Router Settings"
2] Then click on the option which says "Advanced Settings" which will take you to the router's configuration page.
3] Lower the MTU (Maximum Transmission Unit) from 1500 to 1400 or less (usually found on your routers main/ basic setup page)
4] Then click on Security tab disable SPI Firewall Protection, uncheck Filter Anonymous Internet Requests...
B] If you haven't installed Cisco Connect then you can log on to the router's user interface using it's default IP address in the browser which is 192.168.1.1 and type in 'admin' as the password leaving the user name field blank. This will take you to the router's web interface and then follow steps as mentioned above to make the changes.
Then check the connectivity status...

Discovering MAC addresses for Switch ports

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