fedora has wrong mac address in arp table

[andres]

Hi Folks,

my istallation of fedora has the wrong mac address in the arp table.
How does this happen and how do fix it?


Any ideas please.

thanx
Andre

[mrsun2005]

What is the command you are using to display the "arp table"?

[andres]

arp or arp -e

[andres]

I used
arp -d <gw ip >
arp -s <gw ip> <correct mac address>
and now I can see out
will arp -s be permanent or do I need to put it in every 5 minutes

[mrsun2005]

Is the arp information the same as the ifconfig -a information?

Example:

ifconfig -a
eth0 Link encap:Ethernet HWaddr 00:06:29:12:23:AD
inet addr:192.168.1.32 Bcast:192.168.1.255 Mask:255.255.255.0
UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1
RX packets:3577287 errors:0 dropped:0 overruns:0 frame:0
TX packets:3417405 errors:0 dropped:0 overruns:0 carrier:0
collisions:255764 txqueuelen:1000
RX bytes:808985656 (771.5 Mb) TX bytes:1810851984 (1726.9 Mb)
Interrupt:10 Base address:0x7c60 Memory:f3eff000-f3eff038
[

arp/arp -e/arp -a
[root@localhost /]# arp
Address HWtype HWaddress Flags Mask Iface
oslo ether 08:00:20:7C:84:48 C eth0
192.168.1.1 ether 00:50:54:FF:3B:E5 C eth0
[root@localhost /]# arp -e
Address HWtype HWaddress Flags Mask Iface
oslo ether 08:00:20:7C:84:48 C eth0
192.168.1.1 ether 00:50:54:FF:3B:E5 C eth0
[root@localhost /]# arp -a
oslo (192.168.1.33) at 08:00:20:7C:84:48 [ether] on eth0
? (192.168.1.1) at 00:50:54:FF:3B:E5 [ether] on eth0
[root@localhost /]#

????
I don't think you are looking at the same MAC address. If you want to make a MAC address permand, do a man page on ethers. Remember, Computers in there local broadcast domain/subnet are not using Ip addresses, they are directly using MAC addresses to talk to each other. If you put in a duplicated MAC address, your network will do funny things.

Give it a try....

Ralf

[andres]

Hi Ralf,

Ifconfig - gives you the local machines network configuration data including the local network cards' mac address, it does not give you your gateway's mac address.

The problem was that the local machine was getting the wrong mac address for the Router's internal interface.
Anyway arp -s <ip address> <mac address>
perminently puts the ip address mac address combination into the arp table on the local machine (since I did not use a temporary flag in the command)

Once I put the correct ip address and mac address in place the problem is solved -- it now works fine.

[mrsun2005]

arp -s is not permanent, next reboot you will be starting over.

Where is the wrong MAC address of your router mapping to? What is the router hardware? Linux as well or cisco?

[andres]

Hi Ralf,

The router is a Cisco, I do not have access to this puppy, but suspect it has some sort of loopback feature set.

Reboot --- ok, I'll add a script to /etc/rc.d/init.d/ to plug in the arp entry I need on reboot.
While this is a good work around -- I'm really interested to know what is causing it.

I'm going to capture the bad mac address and then get the router folks to see if they can identify what ip address its associated to and from that see if we can isolate the culpret machine and configuration.

thank you for your input -- I appreciate it.