Jens’ BLOG

I just found a Cisco bug in 12.4(20)T1: The ipv6 command is working on the wireless interface. This is fixed in all other version I tried including 12.4(24)T3, 15.0(1)M3 and 15.1(2)T. Who wants to use IPv6 over wireless LAN anyway?

Cisco, ipv6

You can find some training materials here.

At the August meeting sage@guug Berlin we’ll also have a talk about Cisco Nexus.

Cisco, networking, sage@guug

Nobody ever buys me something like this…

Cisco, FUN

I made a joke that “cisco” is the default password on most Cisco systems because they use it in theire documentation and training material. A colleague wouldn’t believe me. Than he asked me if I could check something on a customers Cisco router when he gets me a user name and password.

Guess what. cisco worked for login and enable.

For those of you who don’t know Cisco: Normally there is no default password. You can only login remotely when you configure remote access via ssh / telnet and a password. Until then you only have access to a serial console.

Cisco, WTF, networking, security

It’s always a problem to keep all your ACLs in a network coherent. Recently I was made aware of a small tool form google which makes managing ACLs on Cisco, Juniper and Linux much easier to handle.

Take a look at Capirca.

Some features, like IPv6 ACL support for Cisco is still missing, but it looks quite promising.

Cisco, Juniper, linux, networking, security

In the latest release candidate of GNS3 support for Juniper (Olive) was added. This enables you to easily integrate some virtual Juniper Routers into your virtual IOS network.

And before you ask: No I will not provide you with any IOS, PixOS or JunOS files.

Cisco, Juniper, networking

I recently reviewed a Cisco router configuration. Access via ssh was disabled and only telnet was allowed from some host. Ok, IOS only supports key authentication starting with IOS 15 but I thing that using an encrypted channel to configure and troubleshoot a router is better than clear text. And ssh is available in the standard image for quite some time.

Cisco, networking, security

In the last couple of weeks I talked to several people who are working with Cisco equipment and didn’t know about the Cisco Output interpreter.

For me it’s one of the most useful tools when troubleshooting Cisco problems. The Output Interpreter can be used to interpret output of different show commands and debug messages for Cisco IOS, PixOS, … In most cases you’ll get some useful answerers including Links to documentation.

It can be found here. You need a CCO login to use the output interpreter, if you’re working with Cisco hardware and don’t have an CCO account, get one.

Cisco

sh ip flow top-talkers is a very nice feature on Cisco IOS to check who are the top talkers in your network right now. Here’s a sample output:

To use sh ip flow top-talkers you have to configure the following:

ip flow-top-talkers
top 5
sort-by bytes


Check the manual / the help prompt for more options.

Cisco, networking