When to use BGP with VPLS, or when to use BGP at all?

‎08-14-2016 08:51 PM



I understand that (given the ubiquitous resources on the web) it is hard to be objective at times in forums, because everyone's experience is a bit different. I'll try not to ramble --- although that's difficult at times, I'll give my background, and finally objective(s). 


So, in summary, I've mostly worked in the core for the SMB space, and periodically enterprise, but haven't really had the chance to get much exposure to the latter (enterprise). Over the past few years I've become a bit obsessive about penetrating the enterprise market and landing a solid role. Fast forward to current, and the leads are beginning to come in, but there are certain concepts that are fuzzy to me, or that I have no practical experience with at all. 


My example is a client that I have with approximately 6 metro sites, the core MPLS maintained by a certain ISP, which generically labels their solution Metro Ethernet (of course very popular now with many ISPs). Pretty generic topology, they use Cisco 1841s as PEs and handoff to our CEs: L3 Brocade switches ... this is the same for all sites. We tag voice with standard 46 DSCP, CoS 5 (or whatever the default mapping is ---- but that's probably extraneous detail). 


Anyhow, I've really been trying my hardest to use this client as a learning platform, namely for understanding VPLS, the general nuts and bolts, route/switch/MPLS, etc. I've read through some literature from various vendors, and I feel like I understand the generic L2VPN setup that VPLS will facilitate (ethernet bridge if you will), as well as basic moving pieces of PE/CE relationship ... what I DO NOT understand at all is how, when, and why you would introduce BGP into this topology --- explained to me like I'm two years old. Don't worry, I work with condescending folks all day, hehe, you won't hurt my feelings. Yes, I've began to tear into complex/comprehensive literature on BGP signalling, etc, but if someone could explain using the topology I've given above ... I feel like it would stick more. 


As soon as I began searching for anything MPLS/BGP related, I'm overwhelmed with tons of information pertaining to MP-BGP or MPLS L3VPNs. That's great, and I'm glad this info can be found in abundance ... but I'm looking for deeper context in more fundamental terms, let's say 50k foot view. Ya know? 


A few caveats: Yes, I understand that different protocols/mechanisms can be used for signalling in MPLS cloud ... but what exactly does that mean? In a metro ethernet topology with only 6 sites, why is it advantageous to use anything other than a few P, PE, and CE routers at and LDP for signalling ... vs BGP for signalling.


Sorry for any perversion of concepts/understanding, you'll have to extend some grace to me as I'm rapidly learning this stuff, but don't have the years of experience in enterprise space as some of you gents do ... although I'd like to get there!


Thanks in advance!

Jesse W.
Sr. Systems/Network Engineer


Re: When to use BGP with VPLS, or when to use BGP at all?

‎08-15-2016 11:01 PM

I think a Juniper "dayone" book on MPLS can help. I do not know the explanation for you, but I too am interested but limited time, so I found a very good source. Check this out and see if it helps. Here is brief intro:


While there are many books and papers available that cover network architecture, MPLS services, and MPLS cores, none put all these subjects together in a “beginning-to-end” walkthrough methodology using all the necessary configuration examples for Juniper routers, with explanations for each configuration. This Week: Deploying MPLS is a seminar-in-abook on the process of designing and standing up a MPLS core, as well as provisioning MPLS services such as L3VPN, VPLS, and Layer 2 circuits. This Week: Deploying MPLS assumes readers have a working knowledge of OSPF or ISIS, iBGP, and eBGP, and have already made a choice as to which IGP to use in their network: OSPF or ISIS. These prerequisites clear the path for an elaborate walk-through deployment of a fault-tolerant MPLS network that includes the “how-to” Junos configurations along with the “why-to” explanations on why some architectural decisions are advantageous and others should be avoided.

[KUDOS PLEASE! If you think I earned it!
If this solution worked for you please flag my post as an "Accepted Solution" so others can benefit..]