Category: MPLS
BGP-Free MPLS Core with Segment Routing
After I created the Segment Routing lab to test the relationship between Node Segment ID (SID) and MPLS labels, I was just a minor step away from testing BGP-free core with SR-MPLS.
I added two nodes to my lab setup, this time using IOSv as those nodes need nothing more than EBGP support (and IOSv is tiny compared to IOS XE on CSR):
Segment Routing Segment IDs and MPLS Labels
In one of my introductory Segment Routing videos, I made claims along the lines of “Segment Routing totally simplifies the MPLS control plane, replacing LDP and local labels allocated to various prefixes with globally managed labels advertised in IGP”
It took two years for someone to realize the stupidity over-simplification of what I described. Matjaž Strauss sent me this kind summary of my errors:
You’re effectively claiming that SRGB has to be the same across all devices in the network. That’s not true; routers advertise SIDs and must configure label swap operations in case SRGBs don’t match.
Wait, what? What is SRGB and why could it be different across devices in the same network? Also, trust IETF to take a simple idea and complicate it to support vendor whims.
Reviving Old Content, Part 2
Continuing my archeological explorations, I found a dusty bag of old QoS content:
- Queuing Principles
- QoS Policing
- Traffic Shaping
- Impact of Transmit Ring Size (tx-ring-limit)
- FIFO Queuing
- Fair Queuing in Cisco IOS
I kept digging and turned out a few MPLS, BGP and ADSL nuggets worth saving:
Reviving Old Content, Part 1
More than a decade ago I published tons of materials on a web site that eventually disappeared into digital nirvana, leaving heaps of broken links on my blog. I decided to clean up those links, and managed to save some of the vanished content from the Internet Archive:
- OSPF Flooding Filters in Hub-and-Spoke Environments
- Implicit and Explicit Null Label in MPLS networks
- Default Routes in BGP
- Filter Excessively Prepended BGP Paths
I also updated dozens of blog posts while pretending to be Indiana Jones, including:
Worth Reading: Seamless Suffering
When someone sent me a presentation on seamless MPLS a long while ago my head (almost) exploded just by looking at the diagrams… or in the immortal words of @amyengineer:
“If it requires a very solid CCIE on an obscure protocol mix at 4am, it is a bad design” - Peter Welcher, genius crafter of networks, granter of sage advice.
Turns out I was not that far off… Dmytro Shypovalov documented the underlying complexity and a few things that can go wrong in Seamless Suffering.
EVPN: The Great Unifying Theory of VPN Control Planes?
I claimed that “EVPN is the control plane for layer-2 and layer-3 VPNs” in the Using VXLAN and EVPN to Build Active-Active Data Centers interview a long long while ago and got this response from one of the readers:
To me, that doesn’t compute. For layer-3 VPNs I couldn’t care less about EVPN, they have their own control planes.
Apart from EVPN, there’s a single standardized scalable control plane for layer-3 VPNs: BGP VPNv4 address family using MPLS labels. Maybe EVPN could be a better solution (opinions differ, see EVPN Technical Deep Dive webinar for more details).
Why Would You Need VXLAN Transport?
It’s amazing how sometimes people fond of sharing their opinions and buzzwords on various social media can’t answer simple questions. Today’s blog post is based on a true story… a “senior network architect” fully engaged in a recent hype cycle couldn’t answer a simple question:
Why exactly would you need VXLAN and EVPN?
We could spend a day (or a week) discussing the nuances of that simple question, but all I have at the moment is a single web page, so here we go…
Why Is MPLS Segment Routing Better than LDP?
A while ago I made a statement along the lines of “MPLS segment routing is the best thing that happened to MPLS control plane in a decade”. Obviously some MPLS-focused engineers disagree with that and a few years ago I decided to write a lengthy blog post explaining the differences between using MPLS SR with IGP (or BGP) versus more traditional IGP+LDP approach.
Obviously, I wasn’t making any progress on that front, so the only way forward was to record a short video on the topic which didn’t work well either because the end-result was a set of three videos (available with free or paid ipSpace.net subscription).
Worth Reading: MPLS and ExaBGP
Jon Langemak is on a writing spree: after completing his MPLS-on-Junos series he started a deep dive into ExaBGP. Well worth reading if you’re enjoying detailed technical blog posts.
Segment Routing Anyone?
One of my readers listened to a podcast where a $vendor described how they found another use case for source routing IPv6 segment routing (SR): 5G networks… and wondered whether SR made a comeback or is about to.
To figure out what segment routing is, watch the webinar we did with Jeff Tantsura a while ago.
I don’t know nearly enough about mobile networks to have an opinion, however…
Using MPLS+EVPN in Data Center Fabrics
Here’s a question I got from someone attending the Building Next-Generation Data Center online course:
Cisco NCS5000 is positioned as a building block for a data center MPLS fabric – a leaf-and-spine fabric with MPLS and EVPN control plane. This raised a question regarding MPLS vs VXLAN: why would one choose to build an MPLS-based fabric instead of a VXLAN-based one assuming hardware costs are similar?
There’s a fundamental difference between MPLS- and VXLAN-based transport: the amount of coupling between edge and core devices.
EVPN with MPLS Data Plane in Data Centers
Mr. Anonymous (my most loyal reader and commentator) sent me this question as a comment to one of my blog posts:
Is there any use case of running EVPN (or PBB EVPN) in DC with MPLS Data Plane, most vendors seems to be only implementing NVO to my understanding.
Sure there is: you already have MPLS control plane and want to leverage the investment.
Synchronizing BGP and OSPF (or OSPF and LDP)
Rich sent me a question about temporary traffic blackholing in networks where every router is running IGP (OSPF or IS-IS) and iBGP.
He started with a very simple network diagram:
Do Enterprises Need MPLS?
Continuing the Do Enterprises Need VRFs discussion, let’s see which enterprise networks might need MPLS.
Do you need VRFs?
Read the previous blog post. If the answer is NO, you can stop reading. Otherwise, carry on.
PCEP and BGP-LS Questions and Answers
Julien Lucek concluded his PCEP and BGP-LS webinar with a lengthy Q&A session addressing all sorts of questions from the audience (to access all videos in this webinar, register here).