VRRP

Peter H. Schmidt writes "As the world increasingly relies upon the Internet and TCP/IP-based networks, their reliability and availability have become pressing topics for both enterprises and service providers. The Internet was designed for resiliency, not the 99.999% uptime of the PSTN, but it is now being required to do both jobs. This book on VRRP -- the Virtual Router Redundancy Protocol -- details the open, RFC-track protocol which has been developed to help ensure that edge router failures can be handled automatically without affecting connectivity." Peter's complete review (below) is interesting even if you never have to deal with the network at this level. VRRP Increasing Reliability and Failover with the Virtual Router Redundancy Protocol author Ayikudy Srikanth, Adnan Adam Onart pages 540 publisher Addison Wesley rating Recommended reviewer Peter H. Schmidt ISBN 0201715007 summary An in-depth review of VRRP that is loaded with helpful and informative details.

Protocols that allow for automatic failover to a backup router have been around for a while, but they are proprietary, including Digital's IP Standby Protocol (IPSTB) and Cisco's more well known Hot Standby Routing Protocol (HSRP). These protocols have been used successfully for years, but as with all proprietary protocols, they lock users into one vendor. Plus, the test of time has shown there are ways in which they can be improved upon. VRRP has been developed in response.

VRRP lets you set up groups of routers to cover for each other, with each group acting like one virtual router with it's own MAC and IP addresses. If the main router in a group should go down, the others will quickly (in under 3-4s, typically) notice and one of them will be elected to take over. VRRP makes it easy to set up multiple routers with multiple WAN connections and make sure that WAN connectivity won't be lost if a router goes down.

As the open alternative to HSRP, you can count on VRRP being widely supported by the router vendors. Even Cisco is shipping it now. If you design, build or install routed networks of any size, VRRP is something you probably need to learn about.

Read This Book!

Let me just say up front that I think this is a very good book, and worth the read. As the title says, it is all about how to increase the reliability and failover capability of your network. VRRP is its subject, but it is treated with a thoroughness and attention to context I have rarely seen in a protocol text. Perhaps that follows from the fact that reliability and availability are only of concern due to economics; few protocols are developed to meet a business need, so most books on them never need to get beyond defining where they fit in their protocol family. Despite the context material, I found it easy to jump to the low-level technical details, yet was somewhat surprised to find myself actively enjoying the extensive introductory material.

Srikanth and Onart have put a wealth of background into the book. The first chapter treats network availability from a theoretical perspective, but does it so clearly and enjoyably that I read it straight through and felt I had learned some valuable new concepts. It also gave me all the context necessary to easily follow their discussion of the need for, conceptual operation of, and benefits from VRRP in Chapter 2.

Part II, comprising Chapters 3-6, presents the protocol, discussing its messages, state machine and issues with different LAN technologies, firewalls, tunnels and VPNs. I found this a useful complement to the RFC. Here is where I found the details I always look for first when confronting a new protocol: how many messages are there, how many states, what kind of implementation trade offs are going to be necessary? I particularly appreciated the abundance of clear, annotated diagrams in this part of the book, though they aren't confined to these chapters alone.

The chapters of Part III concern themselves with managing VRRP, and what is noteworthy here are the numerous examples of how you can configure and manage realistic scenarios. Juniper and Nortel routers are used in the examples, and you are given step by step instructions on using SNMP, the CLIs and a GUI (HP Openview). If I had to set a customer up with a redundant router configuration tomorrow, I would grab these chapters first thing.

Part IV may be the most useful part of the book for the experienced network engineer. Chapter 10 presents an excellent discussion of the pros and cons of VRRP vs HSRP and IPSBP, and includes some nice summary tables. Chapter 11 discusses the future of VRRP, and answered many of the niggling "How would it handle this scenario?" questions which had popped up as I read how the current VRRP works.

The final section of the book is comprised of 200 pages of appendices. They start with a moderately brief but well done overview of TCP/IP and IP networks. That is followed by the complete VRRP MIB. Then we are given Linux source from http://w3.arobas.net/~jetienne/vrrpd/ and a nice commentary on it. Next is a thorough explanation of the SDL (Specification and Description Language) and flowcharts which were used to define the state machine in Part II. And if this isn't enough rigor for you, you'll be pleased that the following appendix using first-order predicate calculus to specify VRRP yet more clearly. (If you don't know what first-order predicate calculus is, just feel lucky and skip that part...) The final appendix covers UML, the Unified Modeling Language, which also is used in Part II to show how VRRP state transitions occur.

What's Not to Like?

There is very little to object to about this book. If it has a fault, it may be that it is a bit too comprehensive. VRRP is actually a fairly simple protocol, and I write that as someone who has designed and implemented protocol stacks for over 8 years. The level of rigor and detail put into VRRP in this book are worthy of something as hairy as OSPF or BGP4. I found myself getting lost in the notational details of their examples at times, they were so exactingly detailed, but I found that if I just looked at the diagram and skipped to the last paragraph, I'd get what I needed. This book would actually make a pretty good reference book on networking in general, there's so much here!

FAQs

What level of experience is needed to make good use of the information in the book?

This book has all the intro material a novice to networking could want, yet has it all so well organized that it is easy for the advanced reader to find the interesting details.

Who will find it most useful? Is there an existing, canonical book that already covers the same ground?

I think this book would be most useful for enterprise network designers, implementers and operations people, no matter what their current skill level. I couldn't find another book on VRRP, so it's good that the only game in town right now is a good book.

Is the book readable as well as technically accurate? Is the language stilted, or natural? Are examples easy to follow?

The book is very readable - unusually so. As for accuracy, I didn't notice anything amiss, and I used to QA stuff like this. Good use of language, and a ton of excellent examples.

Is the depth appropriate?

This book dives deep, but not without plenty of warning and acclimatization first for people not quite ready for the open ocean.

Are the illustrations appropriate and well executed?

Excellent, clear illustrations.

Do any extras come with the book, like a CD-ROM of additional information or code samples?

You get a full printout of the VRRP MIB, as well as commented source code.

What's missing from the book? Would it benefit from illustrations, a better index, a final chapter on practical applications?

Nothing significant.

You can purchase VRRP from bn.com. Slashdot welcomes readers' book reviews -- to see your own review here, read the book review guidelines, then visit the submission page.

Comments

Patent issues?

[paja]

Is there any mighty /dotter, who can present royalty/patent status of IBM and Cisco claiming, that parts of VRRP are patented by these companies?

Wow!

[stratjakt]

This guy sure is excited about this book.

I'm excited that Sominex is now available in paperback form.

This is the type of stuff I read on a need-to-know basis.. Ie; I need to implement it, so I get the book. Until then, just knowing what VRRP stands for is enough for most.

Re:Wow!

[Anonymous Coward]

I really can't believe someone managed to write a book on this. VRRP itself (as in the protocol) is dead simple, which is why it's absurd that cisco got a patent on it. its so simple that it basically the same concept as HSRP, which is why the cisco patent does apply to VRRP, so it's not open/free at all.

where things do get a bit more complex, is in the decision processes that specific implementations feed into setting priorities in VRRP packets. if you say, this VRRP instance has priorty 200, but less 20 if interface X goes down, which makes for a imensely more useful VRRP implementation, you start infringing more patents. nortel have one in europe i think that covers adjusting priorties according to interface states, i think theres a more general one too that bases decision on the presence or lack of specific routes in the routing table.

until these patents expire, vrrp is a closed protocol. but, it's soo simple anyway, that unless you are specifically concerned about interoperating with other boxes on the network, there is usually "another way" that's "just as good".

the most interesting thing about vrrp is that it makes a very clear case of how patents can be abused to the disadvantage of non-corporations.

Re:Reliability of TCP

[Anonymous Coward]

TCP isn't the whole story tho. Don't forget aobut those UDP nameserver lookups...

We're dealing with the IP level here.

The internet is supposed to be reasonably intelligent about routing traffic around broken hardware, but the hardware that performs this task is not designed to be redundant/resilliant.

i.e. if your core router breaks, your core breaks.

VRRP is all about getting two routers/firewalls to act as a single unit, intelligently failing over as required.

I've been using VRRP for about 5 years now on Nokia IPSO and Linux boxes. I have to say it's a great solution. It really does mean that all your problems are config errors. Hardware failure is not an issue.

Not Open enough for OpenBSD

[ostiguy]

Cisco maintains patent encumberances upon VRRP - if you use/sell VRRP, and get into a completely unrelated patent/licensing/whathaveyou war with Cisco, Cisco maintains the right to seek damages for your use of VRRP.

I have come to see the merits of this position (dhartmei@ makes a good case, btw ;-) ) . The OpenBSD guys have been sitting on a VRRP package for *years* that they cannot include because this is not really an open standard.

Why does Cisco do this? It may be that they are pissy because HSRP wasn't accepted as the standard. Or they might be looking for protection as they might be afraid other people could have patent claims against stuff that might underlie VRRP - and thus these encumberances could allow them to enact a legal war of attrition as each side has competiting patent claims that would ensure deadlock.

ostiguy

No Open Source implementation because of Patent?

[gehirntot]

From reading the web, it seems that no open source implementation is possible unless a license has been obtained from Cisco.

I am not aware of any open source project that has ships VRRP. The IETF has received more information from Cisco about their Intellectual Possession in regards to VRRP.

Publisher's site/sample chapter.

[gatekeep]

Here's the publisher's page on this book. It even includes a sample chapter.

Enjoy

VRRP OpenSource code

[andi_nip]

I am very VERY surprise that nobody is talking about Keepalived (www.keepalived.org). This is the most advanced VRRPv2 code available in the OpenSource community. In addition it extend VRRPv2 rfc with a synchronization instances code that is very usefull for making persistent routing path. many extensions available.... Keepalived is wonderfull code after 2 years of debugging it is now STABLE and ready for production. the old code from jerome etienne is very draft and really not secure... look at Keepalived if you want to play with VRRP on linux.

Reliance on Secondary Routing Protos...

[jcostom]

I work for Nokia, though don't speak on behalf of the company.

One problem with VRRP v2 as it stands today. Imagine a case where you have two parallel routers and are running VRRP. If you experience an interface failure on your primary router. Ok, that interface fails over to the secondary unit. Since you only experienced an interface failure (let's suppose this is a pair of edge routers), say on the outside. Because the inside i/f of the router is still up, you need a secondary routing protocol to direct the traffic to the secondary router - introducing an asymmetric routing condition. This is easily done with OSPF.

Consider the case, however, that we're no longer talking about routers, but instead firewalls. This condition can wreak havoc with your firewalls state tracking mechanism if your firewall's connection state tracking mechanism is either not shared with the redundant unit, or your connection is fast enough that reply packets arrive before connection data is sync'd.

Enter extensions to VRRP like VRRP Monitored Circuits (aka VRRPmc), from Nokia. If you're running Nokia firewalls (which run Check Point for those who don't know), you're probably using VRRPmc.

When you configure VRRPmc, you monitor the other interfaces in use for VRRP. If one of those other interfaces goes down, you decrement your VRRP priority value by a pre-defined delta value, which if you've calculated correctly, will cause the primary unit to begin advertising VRRP priorities that are lower than what the secondary unit is advertising, thereby causing the virtual ips/macs to shoot over to the secondary unit, rather than just the i/f that failed. On the wire, it still looks like good old VRRP. I'd like to see either the monitored circuits method, or something similar implemented in the mainstream VRRP protocol.