Saturday, July 23, 2011


Well, it's been a while since I've updated this blog, but my CCIE studies continue, and I'm always on the lookout for new and exciting advances in the networking arena. Today marks the official 'release' or ratification of the new protocol TRILL (also known as Routing Bridges or RBridges). Here are the RFCs that were just released that relate to TRILL:

Routing Bridges (RBridges): Base Protocol Specification
Transparent Interconnection of Lots of Links (TRILL) Use of IS-IS
Routing Bridges (RBridges): Adjacency

In short, what TRILL accomplishes is link-state routing (IS-IS) for Layer 2 Ethernet MAC addresses in a LAN, which eliminates the need for the Spanning-Tree Protocol. It is not designed to span outside of a LAN.

TRILL has been implemented in the Nexus 7000 line for some time now, and is also of discussion as a possible component of the much anticipated Juniper QFabric. It is one of the hot topics of discussion for next generation data center designs. The reason I say 'next generation' is the fact that I have yet to see or read about it implemented in production.

Here's a pretty good excerpt from the RFC that gives a general overview of how TRILL works:

RBridges run a link state protocol amongst themselves. This gives
them enough information to compute pair-wise optimal paths for
unicast, and calculate distribution trees for delivery of frames
either to destinations whose location is unknown or to
multicast/broadcast groups [RBridges] [RP1999].

To mitigate temporary loop issues, RBridges forward based on a header
with a hop count. RBridges also specify the next hop RBridge as the
frame destination when forwarding unicast frames across a shared-
media link, which avoids spawning additional copies of frames during
a temporary loop. A Reverse Path Forwarding Check and other checks
are performed on multi-destination frames to further control
potentially looping traffic (see Section 4.5.2).

The first RBridge that a unicast frame encounters in a campus, RB1,
encapsulates the received frame with a TRILL header that specifies
the last RBridge, RB2, where the frame is decapsulated. RB1 is known
as the "ingress RBridge" and RB2 is known as the "egress RBridge".
To save room in the TRILL header and simplify forwarding lookups, a
dynamic nickname acquisition protocol is run among the RBridges to
select 2-octet nicknames for RBridges, unique within the campus,
which are an abbreviation for the IS-IS ID of the RBridge. The
2-octet nicknames are used to specify the ingress and egress RBridges
in the TRILL header.

Multipathing of multi-destination frames through alternative
distribution trees and ECMP (Equal Cost Multipath) of unicast frames
are supported (see Appendix C).

Tuesday, April 12, 2011

Cisco Releases IOU to the Masses

So finally Cisco has released their coveted IOU (IOS On Unix) that has been internal only to Cisco for many years. In a nutshell, it is an emulator that can run any normal IOS code as it would on actual equipment.

The catch now is that they are releasing it under Cisco Learning Labs, and you can't just download the software yourself to use, you must rent labs like you would for an actual rack of Cisco gear for IE studying. Still not good enough Cisco.

Currently, they only have labs for CCNA ICND2, CCNP ROUTE, CCNP SWITCH, CCNP TSHOOT and CCIP MPLS, which will cost $75 for 25 hours (only $50 for CCNA lab). Additional 5 hour blocks can also be added for an additional $20.

More information here:

Tuesday, February 8, 2011

802.11ac - The Upcoming WiFi Standard

Well the IEEE Task Group for 802.11ac has been making good progress, and has recently announced that they hope to have a draft completed by 2011 and products supporting the draft standard by 2012.

The new 802.11ac standard is the next upcoming WiFi protocol that will support speeds up to 1Gig speeds. From what I can decipher so far, it appears to be achieving the high throughput utilizing 256-QAM encoding, and a combination of 80Mhz[+80Mhz] and 160Mhz channels (and still supporting down to 20Mhz channels) formed out of the 5Ghz spectrum with MU-MIMO (multiple user - multiple in multiple out) stream/antenna usage.

Keep up to date on the matter via the IEEE webpage for TGac:

And if you really want to read up on the technical details, here is the latest TG MS Word document:

Saturday, February 5, 2011

Awesome CCIE Quick Review Guide

I recently stumbled across this gem while randomly perusing networking forums. This guide, created by Krzysztof Załęski at, uses a technique called 'mind mapping', and I'm a fan of it for quick technology refreshing.

Check out his blog for updates to the guide, or download the guide here:

Wednesday, February 2, 2011

IPv4 Address Space Exhaustion

Well as made pretty clear from the media recently, the shortage of IPv4 address space is getting close to 'no more' IPv4 address space. Within the past week, APNIC requested the last two available /8 networks to be distributed in its region. The five remaining /8's are now about to be distributed equally (per an ICANN policy) to each of the five Regional Internet Registries (RIRs), which are ARIN, RIPE NCC, APNIC, LACNIC, and AfriNIC.

Posted on the NRO website yesterday is note about a 'significant announcement' happening tomorrow (February 3, 2011) at 9:30am EST. They also mention that the event will be broadcast live over the Internet at It's pretty obvious that this is the event where the final 5 /8 networks are being allocated, as well as showcasing the dire need for IPv6 adoption.

Be sure to tune in to witness a pretty big piece of Internet history!