10 years anniversary

So it is a 10 years anniversary of this blog and with it there is a new challenges ahead. Due to series of unfortunate events I have lost all the content of this blog and all its backups. Though it is quite painful to see 10 years of one’s work gone I see it also as an opportunity for a fresh start. So what going to happen here next ? Well I have couple of things I would like to write about which I haven’t so far so that will be the new content.  read more

How to test IPv6 with iperf

Lately there has been yet again a big surge of interest in IPv6 and I did find to my surprise that even thought IPerf supports IPv6 for quite some time no-one actually has written how to actually do this rather trivial test.
First thing about IPv6 is that your interface on the end-point PCs will auto-assign a link-local address to itself. The link local address is in fe80::macaddress format (where one bit of the mac address can be changed depending on the implementation). So this looks fine – no problems. You should be able to ping between those ip addresses using ipv6 ping riight? Lets try to ping localhost’s ipv6 link-local address. In order to do this you need to specify the interface you are using as ping can’t lookup the address automatically as it can with IPv4. read more

DHCP option 82 and DHCP relay

I was actually playing with DHCP relay and what I did find out is kind of interesting. For what is DHCP relay look for rfc3046 .
In short it is when the client sends a DHCP a broadcast message (discover) some device  – usually the switch that is the client directly connected to – intercepts the packet and sends a unicast discover instead of it to remote server over L3. The advantage is that the amount of boadcasts in the networks drops and secondly the DHCP server can be in different subnet. This is great because you can now use centralised dhcp server for all networks. read more

Unlocking cisco devices for unsupported SFPs

Cisco as well as many other vendors locks their equipment to only work with their own branded SFPs. The problem is that none of the big vendors actually manufactures the modules themselves – they use 3rd parties like avago or finisar. This extremely shameful practice is wide spread so almost everyone does this – Cisco, Juniper, Brocade or NetApp all are guilty of this. One issue is price – the aforementioned companies are willing to ask you 10 or even 100 times more for a branded sfp under the pretense of supportability.  read more