Articles tagged with cisco ios

  1. IP Cache Flow - Find Abusive Hosts

    Posted on in Networking

    If you're on a router that does a lot of traffic, finding the source (or destination) of abusive hosts can be problematic. The output from show ip cache flow can be extremely long and finding anything useful can take a very long time. The following IOS regular expressions (regexes?) can …

  2. Cisco Break Sequence for Outgoing Telnet and SSH Sessions

    Posted on in Networking

    There are a few network devices out there that allow you to connect, but don't give you an option to disconnect. For example, you might be stuck at a password prompt, but have no authentication details. Most telnet clients allow you to break these connections with the ^] (control-]) command. <acronym …

  3. Cisco Catalyst 12.2(46)SE May Break SNMP ifIndexes

    Posted on in Networking

    This week I tried upgrading a Cisco Catalyst 2960 to the newest software release — 12.2(46)SE. The upgrade went just fine, but I noticed that the monitoring software was throwing SNMP errors.

    In case you don't know much about SNMP, an ifIndex identifies a specific interface on a …

  4. Cisco, NAT, and Port Range Stupidity

    Posted on in Networking

    inquisitive (photo by windchime)Anyone who has ever done anything remotely "interesting" with a run-of-the-mill broadband router is undoubtedly familiar with the concept of port forwarding. In the case of some applications (<acronym title="Peer-to-Peer">P2P</acronym> comes immediately to mind, but the <acronym title="Real-time Transport Protocol">RTP</acronym> part of <acronym title …

  5. The Annoyance of 'show config'

    Posted on in Networking

    How many times has this happened to you?

    SLAP#write memory
    startup-config file open failed (Device or resource busy)
    

    If you work in an environment where multiple users have enable access on Cisco devices, you've probably seen it more than once. This particular error is caused when another user has …

  6. Implement a Sensible Naming Policy in Cisco IOS

    Posted on in Networking

    It used to be that access lists in Cisco IOS were numbered. Not only were they numbered, but the numbers were significant to what kind of access list they were. Now access lists (and just about everything else) can be named rather than numbered. Although this seemingly innocuous change has …

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