DHCP Scope: Full of BAD_ADDRESS Entries
Feb05

DHCP Scope: Full of BAD_ADDRESS Entries

KB ID 0001651 Problem I had a client machine struggling to get an DHCP address, and when I looked in DHCP the scope it was full of this; BAD_ADDRESS This address Is Already in Use Solution A tour of Google and forums is full of posts by people with this problem, and other than, ‘Oh I looked in the logs and fixed it’ (with no mention of what log, or where this log was), or ‘Yeah I used Wireshark and located a problem...

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Cisco Catalist Upgrading 2900, 5500 and 3700 Stacks
Dec23

Cisco Catalist Upgrading 2900, 5500 and 3700 Stacks

KB ID 0001630 Problem People are often nervous about doing this, I’m not sure why because Cisco have made it painfully simple now. That’s because instead of the old /bin files we used to use, you can now upgrade a switch (or a switch stack) using a .tar file with one command, (and it will also upgrade all the stack members and the firmware on any other network modules you have in the switches at the same time). Yes it does...

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macOS – SSH Error ‘No Matching Exchange Method Found’
Sep13

macOS – SSH Error ‘No Matching Exchange Method Found’

KB ID 0001245  Problem Note Certified working all the way up to macOS Catalina version 10.15.3 I thought my RoyalTSX had broken today, I upgraded it a couple of weeks ago, and I upgraded to macOS Catalina 10.15 the other day. After this, all my SSH sessions refused to connect with this error;   Unable to negotiate with x.x.x.x port 22: no matching key exchange found. Their offer diffie-hellman-group1-sha1 Note: You may also see the...

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Cisco IOS: Ether-Channel Trunks
Apr08

Cisco IOS: Ether-Channel Trunks

KB ID 0001533 Problem This is a subject that every time I need to create an Ether-Channel I end up checking beforehand, so it’s about time I wrote it up. We are combining two different things, an Ether-channel, (an aggregation of links) and a Trunk (the ability to carry many VLANS). If you are NOT from a Cisco background then you might want to read though the following post first to avoid confusion about the world...

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Cisco Stacking 2960-X Catalyst Switches
Jun05

Cisco Stacking 2960-X Catalyst Switches

KB ID 0001444 Problem You can stack up to 8 2960-X Switches*, you will require the stack modules and cables, (shown below).  *Note: If you are studying for an exam, and the question is StackWize the answer is 9. Solution Stack Modules: Power down the switch, remove the blanking plate and fit the module, then when powered on you can use a show inventory command to make sure the module has been detected correctly. Switch#show inventory...

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Cisco Error ‘%PHY-4-SFP_NOT_SUPPORTED’
Sep13

Cisco Error ‘%PHY-4-SFP_NOT_SUPPORTED’

KB ID 0001347  Problem This is another question I see getting asked a lot in forums! You see something like the following; 000032: *Sep 28 09:35:32.507 UTC: %PHY-4-SFP_NOT_SUPPORTED: The SFP in Gi3/0/50 is not supported (PNL-3750-Stack) 000033: *Sep 28 09:35:32.507 UTC: %PM-4-ERR_DISABLE: gbic-invalid error detected on Gi3/0/50, putting Gi3/0/50 in err-disable state (PNL-3750-Stack) The usual response is ‘Enable unsupported...

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