During my last Building IPv6 Service Provider Core webinar I got a lot of questions about IPv6 over PPPoE (obviously we’re close to widespread IPv6 implementation; I never got PPPoE questions before). I wanted to test various scenarios in my IPv6 lab and thus enabled PPPoE on an Ethernet link between CE and PE routers.

This time I wanted to test multiple configurations in parallel ... no problem thanks versatile PPPoE implementation in Cisco.

It looks like everyone (and their dog) is writing about DCB and FCoE these days, but occasionally we get a fresh thought: Ron Fuller compares FC/Ethernet to East/West coast mentality. Great analogy ;)

Recently I’ve stumbled across a year-old post by James Ventre describing the reasons output rate on an Ethernet-type interface (as reported by the router) never reaches the actual interface speed. One of them: inter-frame/packet gap (IPG).

I was stunned ... I remember very well the early days of thick/thin coax Ethernet when the IPG was needed for proper carrier sense/collision avoidance detection (probability of a collision decreases drastically as you introduce IPG), but on a high-speed point-to-point full duplex link? You must be kidding.

Participants of my webinars might remember the concept of on-site workshops that I kept mentioning until the COVID-19 pandemic brought my in-person business to a halt. Almost a decade before that calamity, the networking team from a large multinational company had decided to test it in practice and invited me for a 3-day DMVPN workshop.

The agenda of these workshops is usually pretty simple:

• Day 1: technology overview and review of the existing network design/challenges.
• Day 2: work on proposed new network design.
• Day 3: tying up loose ends and preparations for pilot/migration.

We agreed on a tentative agenda along these lines and I prepared the material for the technology overview using parts of my Choose the Optimal VPN Service webinar (to compare DMVPN with other VPN solutions) and the DMVPN webinar. Oh boy, was I in for a surprise.

A while ago Ron sent me an intriguing question: “Is it possible to have two EIGRP AS numbers in the same VRF?” Obviously he’s working on a network with multiple EIGRP processes (not an uncommon pre-MPLS/VPN solution; I did a network design along the same lines almost 20 years ago).

It’s easy to run multiple EIGRP autonomous systems in the global IP routing table; just create more than one EIGRP process. They can even run over the same set of interfaces. EIGRP-in-a-VRF implementation is slightly different; you configure an address family within another EIGRP process and (optionally) specify an AS number that does not have to match the AS number of the EIGRP process.

Ethan Banks is continuing his deliberations on going independent (or not). He’s definitely collected some very interesting feedback.

Stephen Foskett shared a link to an interesting blog post: “How to Pitch A Tech Blogger”. A must read for vendors attending Tech Field Day (have you noticed there is no mention of Gartner or IDC? ;)

If you ask any networking engineer building layer-2 fabrics the traditional way about his worst pains, I’m positive Spanning Tree Protocol (STP) will be very high on the shortlist. In a well-designed fully redundant hierarchical bridged network where every device connects to at least two devices higher in the hierarchy, you lose half the bandwidth to STP loop prevention whims.

Enhanced Transmission Selection (ETS) is the second part of the Data Center Bridging puzzle (I’ve already described Priority Flow Control). It specifies two different technologies:

• Queuing mechanisms in bridges
• Data Center Bridging eXchange protocol: a Control/Negotiation protocol that allows bridges and hosts to negotiate QoS parameters in a bridged network.

Although some bridges from some vendors supported numerous QoS mechanisms in the past, 802.1Qaz is the first attempt to standardize a richer set of QoS behaviors than the strict priority queuing defined in 802.1p.

“Use FC where you feel you need to, use Ethernet (NFS, CIFS, iSCSI) everywhere else -- and save money and effort in the process”

Etherealmind and myself have been singing this song for quite some time (probably upsetting a few people working for my favorite vendor), but this time it comes straight from EMC’s CTO. And he didn’t even mention FCoE in his list of storage protocols.

Someone mentioned a while ago in a comment to one of my blog posts that the Nexus 4000 switch already supports multihop FCoE. Now that we know what multihop FCoE really is, let’s see how Nexus 4000 fits into the picture.

The Cisco Nexus 4000 Series Design Guide starts with a confusing set of claims:

• The Cisco Nexus 4000 Series Switches provide the Fibre Channel Forwarder (FCF) function.
• Nexus 4000 is a FCoE Initialization Protocol (FIP) snooping bridge.