Tag: Cisco

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What is Cisco Meraki?

Cisco Meraki is a product range from Cisco, providing a complete range of networking products, from access points to switches to firewalls, and even security cameras. They are powerful, packed with features, yet so simple to use. Let’s see what they have to say about themselves: Cisco Meraki is the leader in cloud controlled WiFi,

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eBGP – ECMP in depth!

My client recently did a fairly big change to the edge network in their data centre, including a migration to 4-byte AS numbers. This wasn’t without it’s challenges. So here is a (long) post about the challenges we faced, and some explanations of some of the more advanced features of BGP such as local-as no-prepend

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Python Scripting on a Cisco Nexus 7k

A few days ago I stumbled upon the python interpreter on the Nexus platform. It got me to tinkering. In the past, I have had a requirement to grab a list of all of the interfaces on a box, the IP’s, and the masks. The interfaces and IP’s can easily be obtained from a show

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Nexus 7000 Software Bug – Flash RAID Errors – 7k Reboot and Failover

It’s been a mad couple of weeks with Nexus 7000’s. My client hit a software bug on their Nexus 7k, which turned out to be a most impressive bug. It basically causes the flash drives to be erroneously marked as faulty, which then causes them to be remounted in read only. The first symptom was

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Replacing a failed Cisco Ironport Web Security Appliance Proxy

Recently we had a Cisco Web Security Appliance (WSA) Proxy fail. When I say fail, I mean a single stick of RAM failed after a reboot. Cisco said RAM isn’t replaceable so we had to RMA the whole box (odd for a device that is basically a rebadged server…maybe I have a money saving idea

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OSPF Network Types – A Neighbour Killer?

While going over some OSPF stuff today, I found a statement saying that OSPF network types have to match for routers for form a neighbour relationship. Because I’m a nerd, I questioned this. My reason? I don’t remember OSPF network type being a field in the hello packet header. And if it’s not in the

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Archiving and deleting IOS images

I recently had the need to upgrade the IOS on a Cisco switch (think it was a 3750). As usual, the flash was too small so I needed to remove (and archive/save) the old IOS before putting the new one on. A lot of the images these days include HTML and other things, so are

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Parser Views – Cisco Security

A post on techexams.net recently made me look into parser views in more detail. I read the section in the CCNA: Security Official Certification Guide about them a while back (the entire one page of it), and never really gave it much thought, but I was prompted by the post on the forum to look into them

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MTU / Fragmentation / ACL Tests – Part 2

Now that ICMP traffic is fragmenting across the network, it’s time to change and start using TCP traffic. This is a follow on from MTU / Fragmentation / ACL Tests….Part 1 and I am aiming to find out what happens to fragmented packets when matched to static extended access lists. I’m going to use a program

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MTU / Fragmentation / ACL Tests….Part 1

There was a throwaway line in a book I was reading (the CCNA: Security Official Certification Guide), that said that a disadvantage of ACL’s is: Does not filter fragmented packets with the same accuracy as non fragmented packets. I have no idea why this is true, and after a post on techexams.net, I decided to just set