Articles in the networking category

1. Most Popular Network Reliability Technologies in 2023

   Posted on July 01, 2023 in networking

   The most popular network reliability technologies in 2023 are:

   • Network automation: This is the use of software to automate network tasks, such as provisioning, monitoring, and troubleshooting. Network automation can help to improve network reliability by reducing human errors and increasing efficiency.
   • AIOps (Artificial Intelligence for IT Operations): This is …

2. What is TCP1323Opts?

   Posted on April 15, 2023 in networking

   TCP1323Opts is a registry value that controls the use of the TCP Timestamp and Window Scaling options. These options are described in RFC 1323, which is an update to the original TCP/IP specification.

   The TCP Timestamp option allows TCP to measure the round-trip time (RTT) between two hosts. This …

3. TACACS Detected 'Invalid Argument'

   Posted on July 29, 2016 in Networking

   As always, I've changed pertinent details for reasons.

   I was working on an ASR the other day and received the follow error:

   RP/0/RSP0/CPU0:ASR9K(config-tacacs-host)# commit
   Fri Jul 29 12:55:46.243 PDT
   
   % Failed to commit one or more configuration items during a pseudo-atomic
   operation. All …

4. [OS X] Disable IPv6 Address Privacy

   Posted on November 13, 2015 in Networking

   For those that are really into privacy, the Privacy Extensions defined in RFC 4941 are a really good thing. This extension circumvents SLAAC and has the result of randomizing your IPv6 address. Like I said, if privacy is a big deal for you, this is definitely something you want enabled …

5. [Cisco] Telnet/SSH work, HTTP Gives Permission Denied

   Posted on August 27, 2012 in Networking

   Here are a few tips that might be helpful if you are having trouble accessing your Cisco router or switch via the web server.

   • Make sure you have the right password! This is pretty obvious, but it's definitely the first thing worth checking.
   • If you're using aaa new-model, you will …

6. Disable Spanning-Tree Per VLAN

   Posted on August 03, 2012 in Networking

   If you need to disable spanning-tree on a particular VLAN in your Cisco-based network, use the following command:

   Switch(config)# no spanning-tree vlan 13
   

   This will disable spanning-tree on unlucky VLAN 13.

   If you have some good examples of why you might want to disable spanning-tree for a VLAN, please …

7. Recover Lost Pre-Shared Keys

   Posted on June 25, 2012 in Networking

   Not everyone has a great password maintenance process. If you run into a situation where the group pre-shared keys for your VPN are lost, you face the option of changing the existing key (and breaking any users that are currently working), or creating a new group with a new key …

8. Cisco IPS Inline Bypass Mode

   Posted on February 06, 2012 in Networking

   On occasion, you may need to put your Cisco IPS into bypass mode. Bypass mode allows the IPS to pass traffic without inspecting it. This may be useful if you suspect the IPS is causing a problem, if you are going to run a one-time scan that would set the …

9. Enabling Stateful Switchover in the Cisco ASR1000

   Posted on December 05, 2011 in Networking

   When you get your brand new Cisco ASR1000 series router, Stateful Switchover (SSO) is disabled by default:

   Router# show redundancy states
          my state = 13 -ACTIVE 
        peer state = 1  -DISABLED 
              Mode = Simplex
           Unit ID = 6
   Redundancy Mode (Operational) = Non-redundant
   Redundancy Mode (Configured)  = Non-redundant
   Redundancy State              = Non Redundant
   

   Enable SSO!

   Router# config …

10. What are BGP Update-Groups?

    Posted on November 21, 2011 in Networking

    You've certainly noticed when look at individual BGP routes on your Cisco routers that the route is advertised to specific update-groups. It isn't obvious from that output just what those update-groups are.

    Router#show ip bgp 8.8.8.8       
    BGP routing table entry for 8.8.8.0/24 …