Jason sent me an interesting question a few days ago: “assuming a vSwitch *did* support MPLS/VPN PE router functionality, what type of protocol support would be needed on the access layer switches?”

While the MPLS/VPN support in hypervisor switches remains in the realm of science fiction, it’s worth knowing that there are at least five different transport options you can use between PE-routers. Here they are, from the most decoupled to the most tightly coupled ones:

Two months ago I wrote the Data Center Fabric Architectures post jokingly defining Borg and Big Brother architectures. In the meantime, a number of vendors have launched (or announced) their fabric products and the post badly needed an update.

I decided to move the updated text to my main web site (where it will be easier to edit), wrote an introductory section, removed a few tongue-in-cheek comments (after all, it’s time to get serious if Cisco’s Data Center blog links to your article) and added numerous links to in-depth articles and examples of individual architectures.

Nosx added a very valid point-of-view to the MPLS/VPN Common Services Design that uses a shared common service Route Target across numerous client VRFs:

This is an overly complex and unsupportable approach to shared services. Having to touch thousands of VRFs to create a shared services VPN is unacceptable. The correct approach is to touch only the "services" vrf, and import/export to each RT that you wish to insert the services into.

As always, the right answer is “it depends.” If you have few large customers, it makes way more sense to add their RTs to the common services VRF. If you have many small customers, adding RTs to the common services VRF does not scale.

My Inbox is (yet again) overflowing with great links.

IPv6

Tassos is describing the DHCPv6 prefix delegation nightmare in great details.

Cut Me Some SLAAC, Or Why You Need RA Guard by Tom the Networking Nerd describes the details of the recently-hyped SLAAC vulnerability. Conclusion: work with a vendor that knows a bit about fixing security problems.

A few days ago I got an interesting question: “What’s your opinion on the IPv6 NDP exhaustion attack and the recommendation to use /120 instead of /64?”

I guess we all heard the fundamentalist IPv6 mantra by now: “Every subnet gets a /64.” Being a good foot soldier, I included it in my Enterprise IPv6 webinar. Time to fix that slide and admit what we also knew for a long time: IPv6 is classless and we have yet to see the mysterious device that dies in flames when sniffing a prefix longer than a /64.

Jeroen sent me an interesting challenge: he would like to reload the router when the 3G WAN interface gets stuck (I thought my Nokia phone is the only one exhibiting this problem, but obviously I was wrong). The reload-on-failed-ping EEM applet I’ve published would be a perfect solution, but it uses track delay and the maximum delay timeout is three minutes, while Jeroen would like to wait 15 minutes before reloading the router.

I got totally fed up with the currently popular “flat-earth with long-distance bridging” architecture paradigm while developing the Data Center Interconnects webinar. It all started with the layer-2 hypervisor switches and lack of decent L3 network-side solutions; promoting non-scalable cloudy solutions doesn’t help either.

The network infrastructure would scale better if the hypervisors would work as MPLS/VPN PE-routers, but even MPLS would hit scalability limits when the number of servers grows into tens of thousands. The only truly scalable solution is IP-over-IP or MAC-over-IP implemented in the hypervisor switches.

A while ago I described what it takes to integrate TRILL backbone with the legacy equipment running Spanning Tree Protocol (STP). Unfortunately, Brocade decided to use a non-standard approach to BPDU handling when implementing their TRILL-like VCS fabric. VDX switches running in fabric mode can either drop incoming BPDU frames or transport them transparently across the fabric to other edge ports. Although VDX switches support STP, RSTP and MSTP (as well as RootGuard and BPDUGuard) when configured as standalone switches, the STP processing is disabled when you configure fabric mode; VCS fabric looks like a huge shared LAN segment to the end hosts and core switches.

2013-03-31: Network OS 4.0 and above supports Distributed Spanning Tree (DiST), for more details read this blog post.

HP’s FlexNetwork architecture launch at Interop has received mixed responses: from pretty positive from Tom the Networking Nerd to cautiously optimistic from Greg (Etherealmind) Ferro and more cautious analysis by Shamus McGillicuddy. For a grumpy skeptic’s take, read my FastPacket blog post.

Few days ago I enjoyed listening to the Teredo-bashing Packet Pushers Podcast during which Greg & the crew simply couldn’t avoid NAT64. Tom even wrote a follow-up post explaining why NAT is bad (we all agree with that) and why we shouldn’t use it in IPv6. Unfortunately he missed the elephant in the room: it’s all about the legacy content. IPv6-only residential users have to access IPv4-only content.