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Missing entries in Mac Address Table?

 
 
Jason
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      02-26-2008
Hi,

I'm studying for my CCNA exam, at some point I inadvertantly cleared all
entries from the mac address table on my 2950 switch, including the CPU
entries. I have recently been noticing some strange behaviour from this
switch, for example with port security not quite working correctly & was
wondering if the two could be related, I have since wiped the switch
(including vlan.dat) but the mac address table is still missing the CPU
entries. I only noticed these missing entries when I did a show mac-
address-table on my other 2950 & saw the difference (see below). How can I
get these entries back & hopefully return my switch to full functionality?
All suggestions greatly received as I have my exam in April & am studying
very hard at the moment.

TIA, Jase



SWITCH1#show mac-address-table
Mac Address Table
------------------------------------------

Vlan Mac Address Type Ports
---- ----------- ---- -----
1 0004.274c.9ca0 DYNAMIC Fa0/1
1 0040.63d8.ba0a STATIC Fa0/12
1 0040.63d8.bab8 DYNAMIC Fa0/4
10 0004.274c.9ca0 DYNAMIC Fa0/1
Total Mac Addresses for this criterion: 4


SWITCH2#show mac-address-table
Mac Address Table
-------------------------------------------

Vlan Mac Address Type Ports
---- ----------- -------- -----
All 000d.28f3.1680 STATIC CPU
All 0100.0ccc.cccc STATIC CPU
All 0100.0ccc.cccd STATIC CPU
All 0100.0cdd.dddd STATIC CPU
1 0004.274c.9ca0 DYNAMIC Fa0/1
1 000a.f4cb.dcc2 DYNAMIC Fa0/1
1 0040.63d8.ba0a STATIC Fa0/11
1 0040.63d8.bab8 DYNAMIC Fa0/1
2 000a.f4cb.dcc2 DYNAMIC Fa0/1
3 000a.f4cb.dcc2 DYNAMIC Fa0/1
10 000a.f4cb.dcc2 DYNAMIC Fa0/1
Total Mac Addresses for this criterion: 11

SWITCH1#show version
Cisco Internetwork Operating System Software
IOS (tm) C2950 Software (C2950-I6Q4L2-M), Version 12.1(11)EA1, RELEASE
SOFTWARE (fc1)
Copyright (c) 1986-2002 by cisco Systems, Inc.
Compiled Wed 28-Aug-02 10:25 by antonino
Image text-base: 0x80010000, data-base: 0x80528000

ROM: Bootstrap program is CALHOUN boot loader

SWITCH1 uptime is 1 hour, 6 minutes
System returned to ROM by power-on
System image file is "flash:/c2950-i6q4l2-mz.121-11.EA1.bin"

cisco WS-C2950-12 (RC32300) processor (revision G0) with 20402K bytes of
memory.
Processor board ID FOC0638Y10G
Last reset from system-reset
Running Standard Image
12 FastEthernet/IEEE 802.3 interface(s)

32K bytes of flash-simulated non-volatile configuration memory.
Base ethernet MAC Address: 00:0A:F4:CBC:C0
Motherboard assembly number: 73-5782-11
Power supply part number: 34-0965-01
Motherboard serial number: FOC06380C9A
Power supply serial number: PHI06350618
Model revision number: G0
Motherboard revision number: A0
Model number: WS-C2950-12
System serial number: FOC0638Y10G
Configuration register is 0xF
 
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Jason
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      02-27-2008
Jason <(E-Mail Removed)> wrote in
news:Xns9A50CC2421934SpamSpamSpamSpanishI@140.99.9 9.130:

> Hi,
>
> I'm studying for my CCNA exam, at some point I inadvertantly cleared
> all entries from the mac address table on my 2950 switch, including
> the CPU entries. I have recently been noticing some strange behaviour
> from this switch, for example with port security not quite working
> correctly & was wondering if the two could be related, I have since
> wiped the switch (including vlan.dat) but the mac address table is
> still missing the CPU entries. I only noticed these missing entries
> when I did a show mac- address-table on my other 2950 & saw the
> difference (see below). How can I get these entries back & hopefully
> return my switch to full functionality? All suggestions greatly
> received as I have my exam in April & am studying very hard at the
> moment.
>
> TIA, Jase
>
>
>
> SWITCH1#show mac-address-table
> Mac Address Table
> ------------------------------------------
>
> Vlan Mac Address Type Ports
> ---- ----------- ---- -----
> 1 0004.274c.9ca0 DYNAMIC Fa0/1
> 1 0040.63d8.ba0a STATIC Fa0/12
> 1 0040.63d8.bab8 DYNAMIC Fa0/4
> 10 0004.274c.9ca0 DYNAMIC Fa0/1
> Total Mac Addresses for this criterion: 4
>
>
> SWITCH2#show mac-address-table
> Mac Address Table
> -------------------------------------------
>
> Vlan Mac Address Type Ports
> ---- ----------- -------- -----
> All 000d.28f3.1680 STATIC CPU
> All 0100.0ccc.cccc STATIC CPU
> All 0100.0ccc.cccd STATIC CPU
> All 0100.0cdd.dddd STATIC CPU
> 1 0004.274c.9ca0 DYNAMIC Fa0/1
> 1 000a.f4cb.dcc2 DYNAMIC Fa0/1
> 1 0040.63d8.ba0a STATIC Fa0/11
> 1 0040.63d8.bab8 DYNAMIC Fa0/1
> 2 000a.f4cb.dcc2 DYNAMIC Fa0/1
> 3 000a.f4cb.dcc2 DYNAMIC Fa0/1
> 10 000a.f4cb.dcc2 DYNAMIC Fa0/1
> Total Mac Addresses for this criterion: 11
>
> SWITCH1#show version
> Cisco Internetwork Operating System Software
> IOS (tm) C2950 Software (C2950-I6Q4L2-M), Version 12.1(11)EA1, RELEASE
> SOFTWARE (fc1)
> Copyright (c) 1986-2002 by cisco Systems, Inc.
> Compiled Wed 28-Aug-02 10:25 by antonino
> Image text-base: 0x80010000, data-base: 0x80528000
>
> ROM: Bootstrap program is CALHOUN boot loader
>
> SWITCH1 uptime is 1 hour, 6 minutes
> System returned to ROM by power-on
> System image file is "flash:/c2950-i6q4l2-mz.121-11.EA1.bin"
>
> cisco WS-C2950-12 (RC32300) processor (revision G0) with 20402K bytes
> of memory.
> Processor board ID FOC0638Y10G
> Last reset from system-reset
> Running Standard Image
> 12 FastEthernet/IEEE 802.3 interface(s)
>
> 32K bytes of flash-simulated non-volatile configuration memory.
> Base ethernet MAC Address: 00:0A:F4:CBC:C0
> Motherboard assembly number: 73-5782-11
> Power supply part number: 34-0965-01
> Motherboard serial number: FOC06380C9A
> Power supply serial number: PHI06350618
> Model revision number: G0
> Motherboard revision number: A0
> Model number: WS-C2950-12
> System serial number: FOC0638Y10G
> Configuration register is 0xF


For anyone who is interested I have solved the mystery of the missing
MAC address table entries & strange switch behavior. It seems that the
switches were running different versions of IOS.

SWITCH1 was running version:

c2950-i6q4l2-mz.121-11.EA1.bin

with SWITCH2 running version

c2950-i6q4l2-mz.121-13.EA1.bin

Once I copied the IOS from SWITCH2 to SWITCH1 everything started working
correctly & the MAC address tables matched. I think the MAC address
table in SWITCH1 was always missing the CPU entries but I only noticed
when compared to SWITCH2, and I wrongly assumed that I had somehow
deleted them - it's all part of the learning curve i suppose.

Jason.
 
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