Articles in the Networking category

  1. TACACS Detected 'Invalid Argument'

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

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

    ::: highlight 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 …
  2. OS X: Disable IPv6 Address Privacy

    Mac OS X logo 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 …

  3. Cisco: Telnet/SSH work, HTTP Gives Permission Denied

    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 …
  4. Disable Spanning-Tree Per VLAN

    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 …

  5. Recover Lost Pre-Shared Keys

    Old Cisco Systems LogoNot everyone has a great password maintenance process. If you run into a situation where the group pre-shared keys for your <acronym title="Virtual Private Network">VPN</acronym> are lost, you face the option of changing the existing key (and breaking any users that are currently working), or creating a …

  6. Cisco IPS Inline Bypass Mode

    Old Cisco Systems LogoOn 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 …

  7. Enabling Stateful Switchover in the Cisco ASR1000

    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 …

  8. What are BGP Update-Groups?

    Old Cisco Systems LogoYou'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 …
  9. Cisco Catalyst NVRAM Corruption

    This is an annoying problem:

    Switch#write
    startup-config file open failed (Not enough space)
    
    Switch#dir nvram:
    Directory of nvram:/
    
    %Error opening nvram:/ (Function not implemented)
    
    1048576 bytes total (1034573 bytes free)
    

    Cisco Catalyst switches simulate NVRAM on their flash. Once in a blue moon, this simulated NVRAM will …

  10. QM FSM Error? Check Your Transform-Set

    If you see an error like the one below in your Cisco ASA log files, check with the other end and make sure your transform-set matches.

    QM FSM error (P2 struct &0xd7fed708, mess id 0xcc86fb64)!
    

    The QM FSM error message usually relates to a configuration mismatch. Although checking the crypto …

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