Extreme Networks Switch – “Error: VLAN Default cannot be disabled because it is configured for an L2 Protocol.”

It is pretty standard practice to disable the default VLAN and renumber its tag ID for security reasons, from version 22.4 and above we often go this issue when performing these basic commands: We’d get the error as below. In our case we don’t want to run STP (Spanning Tree Protocol) because we’re using either […]

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Monitor Rx and Tx Errors on Extreme Networks Switches via SNMP Query (using NagiosXI)

It is helpful to monitor the RxErrors and TxErrors on ports on Extreme Networks switches to get a heads up on any issues before they begin to impact service. The Extreme Networks MIB can be downloaded from the Extreme Networks support portal to assist you in finding the relevant SNMP OIDs, the below is an […]

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Active Directory Certificate Services (ADCS) PKI Domain Admin Vulnerability

Microsoft have published a vulnerability: https://msrc.microsoft.com/update-guide/vulnerability/ADV210003 which allows an attacker to use the NTLM authentications to begin an attack chain to make an unauthenticated NTLM connection that is then relayed to allow a connection to the Active Directory Certificate Services (ADCS), this assuming the auto-enrollment is enabled means that an attacker can make a request […]

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What’s the Difference Between UPC and APC (LC) Connector?

A single-mode or multi-mode duplex fibre optic patch cable a simple enough item, commonly you’ll find these with an LC connector on the end. What are the types? The default type is typically a UPC (Ultra Physical Contact) type connector, if you were to ask a supplier for a fibre patch cable this is normally […]

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Dell Openmanage DNS Records for Server Initiated Discovery (with Microsoft DNS)

OpenManage Enterprise version 3.4 allows automatic discovery of servers that have iDRAC firmware version 4.00.00.00 or later. The appliance can be configured to allow these servers to automatically locate the console by querying the DNS and initiate their discovery. The instructions (and this) give the use of the TUI or manual creation for Dell Openmanage […]

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Putty.exe – “Couldn’t agree a key exchange algorithm”

I had this issue today, on a host that had recently had a software upgrade. Problem: A host to which I was connecting with SSH gave this error: “Couldn’t agree a key exchange algorithm (available: Curve25519-sha256@libssh.org, ECDH-sha2-nistp521, ECDH-sha2-nistp384, ECDH-sha2-nistp256)”. Solution: In my case I updated to a later release of Putty.exe and the issue was resolved. […]

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Leaky Print Spooler Vulnerability (CVE-2021-1675)

So it appears that there is a vulnerability identified in Microsoft Windows machines running Active Directory, this is covered on the Register: https://www.theregister.com/2021/06/30/windows_print_spool_vuln_rce/ Until you patch this you can just disable the “Printer Spooler” service on your Domain Controllers and well to be honest you don’t need this running on the Domain Controller anyway. Edit: […]

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